I am turning a small box room into a wet room with a high flow shower.
However id like to keep running cost right down so am considering trying to
recover the heat in the waste water going down the plug hole to preheat the
cold water going into the thermostatic shower valve.

I cant seem to find any products for sale in the uk that do this, so am
considering making one myself.

Has anyone had a go at building one?

Steve

"R.P.McMurphy" wrote in message
...
I am turning a small box room into a wet room with a high flow shower.
However id like to keep running cost right down so am considering trying to
recover the heat in the waste water going down the plug hole to preheat the
cold water going into the thermostatic shower valve.

I cant seem to find any products for sale in the uk that do this, so am
considering making one myself.

Has anyone had a go at building one?

Steve

I'm thinking of the same thing myself, but don't know of any product. On
problem is that the waste water contain scum and hair, bits of soap etc, and
it's low pressure so cannibalising a boiler heat exchanger won't work. I'm
thinking of coiled microbore piping ( several in parallel ) inside a flat
box where the waste water can hang about for a few seconds. The other option
is to redirect the trap outlet so that it goes to a length of 40mm waste
pipe inside which some copper tube could be coiled for the cold water, the
40mm waste eventually conecting back up with the old waste outlet.

many configurations possible, all with small problems involved

Andy

R.P.McMurphy brought next idea :
I am turning a small box room into a wet room with a high flow shower.
However id like to keep running cost right down so am considering trying to
recover the heat in the waste water going down the plug hole to preheat the
cold water going into the thermostatic shower valve.

I cant seem to find any products for sale in the uk that do this, so am
considering making one myself.

I would run an outlet copper pipe close to the cold inlet for as long a
distance as possible, perhaps ensuring good thermal contact by
soldering the two side by side and wrapping insulation round the pair.
The larger the two pipes and slower the flow through them, the more
heat will be transfered between them.



--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

R.P.McMurphy wrote:
I am turning a small box room into a wet room with a high flow shower.
However id like to keep running cost right down so am considering trying to
recover the heat in the waste water going down the plug hole to preheat the
cold water going into the thermostatic shower valve.

I cant seem to find any products for sale in the uk that do this, so am
considering making one myself.

Has anyone had a go at building one?

Steve


I havent, so take any info with this in mind. I figured a good idea
might be to wrap 4 equal lengths of microbore round the copper drain
pipe, soldering in place, and parallelling the microbores using a 4:1
manifold at each end. Typical lengths are 2-3' for the unit.

Reasons for paralleled microbo
1.you get much more contact area with the drain pipe than you would
with larger pipes
2. its easy to spiral it round by hand
3. Differential thermal expansion should not cause any serious
problems. (untrue of long straight pipes in parallel)
4. Due to microbore flexibility, the finished structure is robust and
leakproof. This is untrue of pipe-in-pipe types.

Best thing to do with this water is to feed it to the cold inlet on a
thermostatic shower, as you said.

If you're creating a setup, there is another way to gain heat at very
low cost, with less return than your drain exchanger. That is to use a
low cost high capacity solar collector between header tank and HW tank,
with draining and bypass valves for winter. By low cost I mean a
pancake of plastic pipe under polythene, on either flat roof or wall.


NT

I havent, so take any info with this in mind. I figured a good idea
might be to wrap 4 equal lengths of microbore

Just a thought here - wouldn`t microbore be more prone to blockages
from hair or anything else that went down the plug`ole ?

(i`ve got sod all experience of plumbing, just a wild question)

--
Please add the word "newsgroup" in the subject line of personal emails
**** My email address includes "ngspamtrap" and " ****

Colin Wilson explained :
Just a thought here - wouldn`t microbore be more prone to blockages
from hair or anything else that went down the plug`ole ?

He was suggesting using the microbore for the cold feed, wrapped around
a copper drain.....

Good idea BTW (using microbore).

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

R.P.McMurphy wrote:
I am turning a small box room into a wet room with a high flow shower.
However id like to keep running cost right down so am considering
trying to recover the heat in the waste water going down the plug
hole to preheat the cold water going into the thermostatic shower
valve.

I cant seem to find any products for sale in the uk that do this, so
am considering making one myself.

Has anyone had a go at building one?

Steve

Oh! its a saving pennies thread. Ho-hum
--
Sir Benjamin Middlethwaite

On Wed, 1 Feb 2006, R.P.McMurphy wrote:

I am turning a small box room into a wet room with a high flow shower.
However id like to keep running cost right down so am considering trying to
recover the heat in the waste water going down the plug hole to preheat the
cold water going into the thermostatic shower valve.

I cant seem to find any products for sale in the uk that do this, so am
considering making one myself.

Has anyone had a go at building one?

No, but I did read a website once by a company (US-based IIRC) who did.
Sorry I don't have the address but I do remember the following:

The right way to do it is to have a *vertical* drainpipe - the falling
water then tends to form a thin film which adheres to the inside of the
pipe. The inside of the drainpipe must be smooth i.e. you can't put a coil
inside the drain pipe - it has to be around the outside. Obviously good
thermal contact between heat carrying parts is essential - you can't just
wrap a coil around; it has to be soldered or brazed. It goes without
saying that plastic is right out, at last for heat transferring components.

As with all heat exchangers, the flow direction of the two fluids should
be opposite otherwise you will never extract more than 50% of the
available heat. i.e. if your drain water is falling vertically then your
cold water flow should be upwards.

I can think of no easy DIY way of continuously brazing a copper spiral to
a central tube. I would think that a more practical design would be to
have two concentric tubes, with the drain flow in the central tube and the
cold water flowing between the central tube and the outer tube.

HTH


--
Alistair Riddell - BOFH
Microsoft - because god hates us

On Wed, 01 Feb 2006 18:49:32 +0000, Harry Bloomfield wrote:

Colin Wilson explained :
Just a thought here - wouldn`t microbore be more prone to blockages
from hair or anything else that went down the plug`ole ?

He was suggesting using the microbore for the cold feed, wrapped around
a copper drain.....

Good idea BTW (using microbore).

This has come up from time to time as a suggestion.

I am fairly sure that copper waste pipe is compatible with the push fit
waste fittings.

A problem I can aticipate if this works is that you will have to keep
upping the flow rate from the electric shower using the
temperature adjuster. You may run out of travel and need to have a shower
which you can then put on half power.

You may well have already thought this through but the outlet from the
microbore pre-heater should be at the plug hole of the bath/shower-tray.

I'd try 'tack' soldering the microbore to the water pipe using potable
'green' lead-free solder every 25cm or so and then come along after
using CH/gas pipe leaded solder (which has a lower melting point) to
finish the job.

It might just be possible to turn a typical 9kW Electric shower into a
20kW shower typical from a combi.

Just to save a +lot+ of hassle I'd put some 1/4 turn bypass isolators
around the gizmo - you'd be pretty ****ed off if you found you could not
get the water through fast enough in August to shower safely.

Note that only the better stocked PMs will have 35/42/50 mm Cu pipe.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

wrote:

I havent, so take any info with this in mind. I figured a good
idea might be to wrap 4 equal lengths of microbore round the
copper drain pipe, soldering in place, and parallelling the
microbores using a 4:1 manifold at each end.

And then wrap the whole thing in thick insulation.

"Ed Sirett" wrote in message
news
On Wed, 01 Feb 2006 18:49:32 +0000, Harry Bloomfield wrote:

Colin Wilson explained :
Just a thought here - wouldn`t microbore be more prone to blockages
from hair or anything else that went down the plug`ole ?

He was suggesting using the microbore for the cold feed, wrapped around
a copper drain.....

Good idea BTW (using microbore).

This has come up from time to time as a suggestion.

I am fairly sure that copper waste pipe is compatible with the push fit
waste fittings.

A problem I can aticipate if this works is that you will have to keep
upping the flow rate from the electric shower using the
temperature adjuster. You may run out of travel and need to have a shower
which you can then put on half power.

You may well have already thought this through but the outlet from the
microbore pre-heater should be at the plug hole of the bath/shower-tray.

I'd try 'tack' soldering the microbore to the water pipe using potable
'green' lead-free solder every 25cm or so and then come along after
using CH/gas pipe leaded solder (which has a lower melting point) to
finish the job.

It might just be possible to turn a typical 9kW Electric shower into a
20kW shower typical from a combi.

Just to save a +lot+ of hassle I'd put some 1/4 turn bypass isolators
around the gizmo - you'd be pretty ****ed off if you found you could not
get the water through fast enough in August to shower safely.

Note that only the better stocked PMs will have 35/42/50 mm Cu pipe.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html


Thanks for all the ideas, I think im going down the
'meter-of-copper-pipe-with-microbore-soldered/braised-to-it' route. where
can I get the copper pipe from of the right size that will fit straight into
the ubend from the shower? what size? also concerned about making sure
flow rate is not restricted....how many 10mm or 8mm microbore will I need to
wrap around the copper waste pipe to keep a free flowing run from the 22 mm
supply?

Oh by the way im not using an electric shower, im using a thermostatic
shower valve, http://tinyurl.com/dwmdb supplied from a 3bar pump
http://tinyurl.com/bl5ou .

Steve

On Wed, 1 Feb 2006 16:44:57 -0000, "R.P.McMurphy"
wrote:

Has anyone had a go at building one?

Loads of people. Go for a simple two concentric tube contra-flow
design. Obviously the drain tube is in the middle, and make this as big
and thin walled as you can. Anything with multiple tubes is asking for
blockage trouble, or slow drainage flow which is nearly as bad. They
need to be concentric or you'll not get a usefully large enough surface
area - it doesn't matter how closely you solder the tubes, it's the
water-copper interface that has the highest temperature drop across it.

Not too much weight of metal, or the steady-state flow might be fine but
it takes too long to warm up,.

Any book on model engineering boilermaking will give you the
construction details, but you can get away with simple flat plate
endplates, you don't have to flange them - just use small bent stakes in
the endplates so as to hold the tubes central while you solder them. Use
silver solder, in two grades, to assemble it. This allows you assemble
it in two stages and still use soft solder to install it in place.

As the drain tube has to run half-empty (or else it will glug) then some
designs use a horizontally squashed oval tube, so as to have better
metal-water contact area with less-full tubes. This is still easy to
make.

Make a simple spreadsheet up too and run the numbers for the heat
transfer - it's worth putting some real figures on it.

On Wed, 1 Feb 2006 16:44:57 -0000, "R.P.McMurphy"
wrote:

I am turning a small box room into a wet room with a high flow shower.
However id like to keep running cost right down so am considering trying to
recover the heat in the waste water going down the plug hole to preheat the
cold water going into the thermostatic shower valve.

Compared with the cost of the water these devices use the fuel cost
is fairly low. Application of some Black Bodge Tape to the shower
head would be far more effective.

--
Peter Parry.
http://www.wpp.ltd.uk/

Alistair Riddell wrote:
On Wed, 1 Feb 2006, R.P.McMurphy wrote:

I am turning a small box room into a wet room with a high flow shower.
However id like to keep running cost right down so am considering trying to
recover the heat in the waste water going down the plug hole to preheat the
cold water going into the thermostatic shower valve.

I cant seem to find any products for sale in the uk that do this, so am
considering making one myself.

Has anyone had a go at building one?

No, but I did read a website once by a company (US-based IIRC) who did.
Sorry I don't have the address but I do remember the following:

The right way to do it is to have a *vertical* drainpipe - the falling
water then tends to form a thin film which adheres to the inside of the
pipe. The inside of the drainpipe must be smooth i.e. you can't put a coil
inside the drain pipe - it has to be around the outside. Obviously good
thermal contact between heat carrying parts is essential - you can't just
wrap a coil around; it has to be soldered or brazed. It goes without
saying that plastic is right out, at last for heat transferring components.

As with all heat exchangers, the flow direction of the two fluids should
be opposite otherwise you will never extract more than 50% of the
available heat. i.e. if your drain water is falling vertically then your
cold water flow should be upwards.

I can think of no easy DIY way of continuously brazing a copper spiral to
a central tube. I would think that a more practical design would be to
have two concentric tubes, with the drain flow in the central tube and the
cold water flowing between the central tube and the outer tube.

HTH


--
Alistair Riddell - BOFH
Microsoft - because god hates us

This has come up in the past. You are right a US company, GFX, makes a
drain heat recovery that works and is feasible. I looked at it in aid
to extend the size of the cylinder. A quick Goggle gives
http://groups.google.co.uk/group/uk.d-i-y/browse_frm/thread/483788ba33e75325/78c747aee553e52f?lnk=st&q=gfx+group%3Auk.d-i-y&rnum=4&hl=en#78c747aee553e52f

R.P.McMurphy wrote:
I am turning a small box room into a wet room with a high flow shower.
However id like to keep running cost right down so am considering trying to
recover the heat in the waste water going down the plug hole to preheat the
cold water going into the thermostatic shower valve.

I cant seem to find any products for sale in the uk that do this, so am
considering making one myself.

Has anyone had a go at building one?

Steve

Just a half-baked idea: How about combining it with a grey water
recovery system? Thus the hot grey water is stored in a tank where it
hangs around giving time for heat recovery until someone flushes the
loo. You could get a good spiral of cold water pipe in the tank.
Perhaps the tank could also cool into a room as "radiator"? Pass the
water to the tank through a radiator? Think on't.

Chris

Alistair Riddell wrote:
On Wed, 1 Feb 2006, R.P.McMurphy wrote:

I am turning a small box room into a wet room with a high flow shower.
However id like to keep running cost right down so am considering trying to
recover the heat in the waste water going down the plug hole to preheat the
cold water going into the thermostatic shower valve.

I cant seem to find any products for sale in the uk that do this, so am
considering making one myself.

Has anyone had a go at building one?

No, but I did read a website once by a company (US-based IIRC) who did.
Sorry I don't have the address but I do remember the following:

The right way to do it is to have a *vertical* drainpipe - the falling
water then tends to form a thin film which adheres to the inside of the
pipe. The inside of the drainpipe must be smooth i.e. you can't put a coil
inside the drain pipe - it has to be around the outside. Obviously good
thermal contact between heat carrying parts is essential - you can't just
wrap a coil around; it has to be soldered or brazed. It goes without
saying that plastic is right out, at last for heat transferring components.

As with all heat exchangers, the flow direction of the two fluids should
be opposite otherwise you will never extract more than 50% of the
available heat. i.e. if your drain water is falling vertically then your
cold water flow should be upwards.

I can think of no easy DIY way of continuously brazing a copper spiral to
a central tube. I would think that a more practical design would be to
have two concentric tubes, with the drain flow in the central tube and the
cold water flowing between the central tube and the outer tube.

HTH


Vertical orientation does maximise efficiency, but isnt practical for
downstairs, and horizontal pipes also work ok.

Soldering a microbore spiral onto the copper drain tube isnt hard in
principle. You just wrap another 1/4 turn on, solder, wrap another 1/4
turn, solder etc. Note you wrap all 4 microbores on in parallel, not
one after the other. Straightforward, pretty slow, probably quite
satisfying.

The xsa of 4x8mm microbores is equivalent to one 16mm pipe, and 4x 10mm
pipes has the xsa of one 20mm pipe.

The idea mentioned of slightly squashing the centre section of the pipe
to ovalise it would of course help maximise efficiency, as long as its
not overly squashed, nor squashed too near the ends.


NT

wrote in message
oups.com...
Alistair Riddell wrote:


The xsa of 4x8mm microbores is equivalent to one 16mm pipe, and 4x 10mm
pipes has the xsa of one 20mm pipe.


Resistance to flow is also strongly dependent on the diameter of the pipe,
ie the distance between peak flow in the middle of the pipe and near zero
flow at the pipe material.

Don't buy a power shower or put your cold inlet inside and lying on the
bottom of the waste pipe so that the warm waste water will heat up the
cold

Fred wrote:
wrote in message
oups.com...
Alistair Riddell wrote:


The xsa of 4x8mm microbores is equivalent to one 16mm pipe, and 4x 10mm
pipes has the xsa of one 20mm pipe.


Resistance to flow is also strongly dependent on the diameter of the pipe,
ie the distance between peak flow in the middle of the pipe and near zero
flow at the pipe material.

yes, since its only a shortish pipe length I didnt want to get into it
too much, but its true enough that reistance will be higher than a
standard 16 or 20mm pipe, so 10mm microbore would probably be a better
choice.

NT

On Wed, 01 Feb 2006 20:56:24 +0000, R.P.McMurphy wrote:


"Ed Sirett" wrote in message
news
On Wed, 01 Feb 2006 18:49:32 +0000, Harry Bloomfield wrote:

Colin Wilson explained :
Just a thought here - wouldn`t microbore be more prone to blockages
from hair or anything else that went down the plug`ole ?

He was suggesting using the microbore for the cold feed, wrapped around
a copper drain.....

Good idea BTW (using microbore).

This has come up from time to time as a suggestion.

I am fairly sure that copper waste pipe is compatible with the push fit
waste fittings.

A problem I can aticipate if this works is that you will have to keep
upping the flow rate from the electric shower using the
temperature adjuster. You may run out of travel and need to have a shower
which you can then put on half power.

You may well have already thought this through but the outlet from the
microbore pre-heater should be at the plug hole of the bath/shower-tray.

I'd try 'tack' soldering the microbore to the water pipe using potable
'green' lead-free solder every 25cm or so and then come along after
using CH/gas pipe leaded solder (which has a lower melting point) to
finish the job.

It might just be possible to turn a typical 9kW Electric shower into a
20kW shower typical from a combi.

Just to save a +lot+ of hassle I'd put some 1/4 turn bypass isolators
around the gizmo - you'd be pretty ****ed off if you found you could not
get the water through fast enough in August to shower safely.

Note that only the better stocked PMs will have 35/42/50 mm Cu pipe.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html


Thanks for all the ideas, I think im going down the
'meter-of-copper-pipe-with-microbore-soldered/braised-to-it' route. where
can I get the copper pipe from of the right size that will fit straight into
the ubend from the shower? what size? also concerned about making sure
flow rate is not restricted....how many 10mm or 8mm microbore will I need to
wrap around the copper waste pipe to keep a free flowing run from the 22 mm
supply?

Oh by the way im not using an electric shower, im using a thermostatic
shower valve, http://tinyurl.com/dwmdb supplied from a 3bar pump
http://tinyurl.com/bl5ou .

As I said in my reply
" Note that only the better stocked PMs will have 35/42/50 mm Cu pipe."
The 42mm pipe will fit in the outlet of the shower trap. And I think it
will fit into pushfit waste fittings aswell as compression type (of course).

Since there are 4x10 to 1x22 'manifolds' available I think you should go
with that on pragmatic grounds.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

Andy wrote:
"R.P.McMurphy" wrote in message
...
I am turning a small box room into a wet room with a high flow shower.
However id like to keep running cost right down so am considering trying to
recover the heat in the waste water going down the plug hole to preheat the
cold water going into the thermostatic shower valve.

I cant seem to find any products for sale in the uk that do this, so am
considering making one myself.

Has anyone had a go at building one?

Steve

I'm thinking of the same thing myself, but don't know of any product. On
problem is that the waste water contain scum and hair, bits of soap etc, and
it's low pressure so cannibalising a boiler heat exchanger won't work. I'm
thinking of coiled microbore piping ( several in parallel ) inside a flat
box where the waste water can hang about for a few seconds. The other option
is to redirect the trap outlet so that it goes to a length of 40mm waste
pipe inside which some copper tube could be coiled for the cold water, the
40mm waste eventually conecting back up with the old waste outlet.

many configurations possible, all with small problems involved

Andy


I would avoid any version with cold pipes inside the drain pipe myself.
You'd soon have these problems:

1. soap, hair, grease build up round the cold pipe, making for much
reduced heat transfer.
2. This muck-catching arrangement causes a pipe block
3. It also causes a foul smell outside, if you have an open drain,
since much muck is perpetually trapped in there.
4. You cant clear it by rodding.
5. And if Murphys law holds true, your drain rod will jam solid inside
the piping.

If you must use a pipe-in-pipe, have the drain as the central pipe.

I would be hesitant to make them this way as diffrential thermal
expansion could cause a lot of stress, and solder is a very soft metal.
Wrapping microbore round the drain pipe eliminates these problems,
though it does mean a fair amount of soldering. Its possible it may
work ok unsoldered, eg with some grease and zinc oxide wiped where the
pipes touch, and just some solder at each end, or maybe even large a
stainless jubilee clip.

BTW theres no point insulating the thing once made. If you've got
insulation to use, put it somewhere on the hot pipe.


NT

wrote:
Andy wrote:
"R.P.McMurphy" wrote in message
...
I am turning a small box room into a wet room with a high flow shower.
However id like to keep running cost right down so am considering trying to
recover the heat in the waste water going down the plug hole to preheat the
cold water going into the thermostatic shower valve.
snip
1. soap, hair, grease build up round the cold pipe, making for much
reduced heat transfer.
2. This muck-catching arrangement causes a pipe block
3. It also causes a foul smell outside, if you have an open drain,
since much muck is perpetually trapped in there.
4. You cant clear it by rodding.
5. And if Murphys law holds true, your drain rod will jam solid inside
the piping.

I was wondering about something like this.
Preliminary design was:

Hair filter.

Channeled plate to take the flow of water and distribute it into an
evenly falling circular curtain of 10cm diameter (or so).
Copper coil, 10cm*30cm or so of close-wound pipe.

Cold comes in at bottom of coil, and leaves top warmed by the water film
flowing over it.

The plus over the american 'coil wrapped round pipe' should be better
heat transfer, without a long vertical drop.
The minus is of course need for occasional cleaning.

To address the cleaning issue, I was planning either to make the coil
completely removable, with something like (but not) hozelok connectors,
or to have the channeled plate removable, so that you have access to the
inside and the outside of the coil in the 20cm*30cm well it sits in.

(The well is designed to never have water sitting in it)

Ian Stirling wrote:
wrote:
Andy wrote:
"R.P.McMurphy" wrote in message
...
I am turning a small box room into a wet room with a high flow shower.
However id like to keep running cost right down so am considering trying to
recover the heat in the waste water going down the plug hole to preheat the
cold water going into the thermostatic shower valve.
snip
1. soap, hair, grease build up round the cold pipe, making for much
reduced heat transfer.
2. This muck-catching arrangement causes a pipe block
3. It also causes a foul smell outside, if you have an open drain,
since much muck is perpetually trapped in there.
4. You cant clear it by rodding.
5. And if Murphys law holds true, your drain rod will jam solid inside
the piping.

I was wondering about something like this.
Preliminary design was:

Hair filter.

Channeled plate to take the flow of water and distribute it into an
evenly falling circular curtain of 10cm diameter (or so).
Copper coil, 10cm*30cm or so of close-wound pipe.

Cold comes in at bottom of coil, and leaves top warmed by the water film
flowing over it.

The plus over the american 'coil wrapped round pipe' should be better
heat transfer, without a long vertical drop.
The minus is of course need for occasional cleaning.

To address the cleaning issue, I was planning either to make the coil
completely removable, with something like (but not) hozelok connectors,
or to have the channeled plate removable, so that you have access to the
inside and the outside of the coil in the 20cm*30cm well it sits in.

(The well is designed to never have water sitting in it)

I guess it would work, yes. Its adding maintenance though. But a 1'
drop, if your bath's on the ground floor you probably wont have that
much room.

Ah: because it would fil with muck and gunge, and people being busy
with more pressing things, you'd end up with such units getting stinky.
I would want to keep any possible stink gen on the other side of the
water trap. But that then makes it inaccessible...


NT

wrote:
Ian Stirling wrote:
wrote:
Andy wrote:
"R.P.McMurphy" wrote in message
...
I am turning a small box room into a wet room with a high flow shower.
However id like to keep running cost right down so am considering trying to
recover the heat in the waste water going down the plug hole to preheat the
cold water going into the thermostatic shower valve.
snip
1. soap, hair, grease build up round the cold pipe, making for much
reduced heat transfer.
2. This muck-catching arrangement causes a pipe block
3. It also causes a foul smell outside, if you have an open drain,
since much muck is perpetually trapped in there.
4. You cant clear it by rodding.
5. And if Murphys law holds true, your drain rod will jam solid inside
the piping.

I was wondering about something like this.
Preliminary design was:

Hair filter.

Channeled plate to take the flow of water and distribute it into an
evenly falling circular curtain of 10cm diameter (or so).
Copper coil, 10cm*30cm or so of close-wound pipe.

Cold comes in at bottom of coil, and leaves top warmed by the water film
flowing over it.

The plus over the american 'coil wrapped round pipe' should be better
heat transfer, without a long vertical drop.
The minus is of course need for occasional cleaning.

To address the cleaning issue, I was planning either to make the coil
completely removable, with something like (but not) hozelok connectors,
or to have the channeled plate removable, so that you have access to the
inside and the outside of the coil in the 20cm*30cm well it sits in.

(The well is designed to never have water sitting in it)

I guess it would work, yes. Its adding maintenance though. But a 1'
drop, if your bath's on the ground floor you probably wont have that
much room.

Ah: because it would fil with muck and gunge, and people being busy
with more pressing things, you'd end up with such units getting stinky.
I would want to keep any possible stink gen on the other side of the
water trap. But that then makes it inaccessible...

A water trap could easily be done simply by making the inlet do:



| |
\wwwwwwwww|wwwww|wnwww/
.\___________________/.
: :
: :
O O
: :
O O


(O = pipe, : = falling water, www = water surface, n = water spirit (nymph, or
similar)

Andy Dingley wrote:
On Wed, 1 Feb 2006 16:44:57 -0000, "R.P.McMurphy"
wrote:

Has anyone had a go at building one?

snip details

Make a simple spreadsheet up too and run the numbers for the heat
transfer - it's worth putting some real figures on it.

That's what I'd be interested in seeing. What actual potential heat
gain is there? How does that translate into energy saved (if you're
into being green) or money saved (if that does it for you)

--
Steve F

Fitz wrote:
Andy Dingley wrote:
On Wed, 1 Feb 2006 16:44:57 -0000, "R.P.McMurphy"
wrote:

Make a simple spreadsheet up too and run the numbers for the heat
transfer - it's worth putting some real figures on it.

That's what I'd be interested in seeing. What actual potential heat
gain is there? How does that translate into energy saved (if you're
into being green) or money saved (if that does it for you)

the one time I calculated this, the payback was excellent. These things
do look like a genuinely good idea.


NT

Ian Stirling wrote:
wrote:

I guess it would work, yes. Its adding maintenance though. But a 1'
drop, if your bath's on the ground floor you probably wont have that
much room.

Ah: because it would fil with muck and gunge, and people being busy
with more pressing things, you'd end up with such units getting stinky.
I would want to keep any possible stink gen on the other side of the
water trap. But that then makes it inaccessible...

A water trap could easily be done simply by making the inlet do:



| |
\wwwwwwwww|wwwww|wnwww/
.\___________________/.
: :
: :
O O
: :
O O


(O = pipe, : = falling water, www = water surface, n = water spirit (nymph, or
similar)


I'm a little unclear about your diagram, so I might have misinterpreted
it, but its starting to look complex to construct and hard to get to
the muck storage to clean it. It seems theres no free lunch.


NT

wrote:
Ian Stirling wrote:
snip
snip
I'm a little unclear about your diagram, so I might have misinterpreted
it, but its starting to look complex to construct and hard to get to
the muck storage to clean it. It seems theres no free lunch.

Hokay. Bigger diagram.



Shower floor. Removable plug

_________________ ____ _____ ___________________
|| |H| ||
|- | | --
| \_____/ |
| : : | | |
warm out| O O |
| : : |
| O O |
| : : |
\ O O / cold in
\ /
\ /
\___ __/
| |
To waste.

H is a removable hair filter. Below that is a circular dish, forming a
trap, over the edge of which the water flows down the heat exchanger
coil.
When you remove the inspection plate, which is a 20cm dia (or possibly square)
door, with a seal round the edge, the trap comes with it.
Then you simply take a bottle brush or something a bit fatter (there is
a 5cm gap round the outside for this purpose) and clean both sides of
the heat exchanger.

I'm envisioning the heat exchanger coil being fairly close wrapped, with
perhaps 5mm gaps between pipes.

Inside the top of the inspection chamber are a couple of lever valves,
to enable the coil to be bypassed, allowing it to be washed with very
hot water.

Ian Stirling wrote:
wrote:
Ian Stirling wrote:
snip
snip
I'm a little unclear about your diagram, so I might have misinterpreted
it, but its starting to look complex to construct and hard to get to
the muck storage to clean it. It seems theres no free lunch.

Hokay. Bigger diagram.



Shower floor. Removable plug

_________________ ____ _____ ___________________
|| |H| ||
|- | | --
| \_____/ |
| : : | | |
warm out| O O |
| : : |
| O O |
| : : |
\ O O / cold in
\ /
\ /
\___ __/
| |
To waste.

H is a removable hair filter. Below that is a circular dish, forming a
trap, over the edge of which the water flows down the heat exchanger
coil.
When you remove the inspection plate, which is a 20cm dia (or possibly square)
door, with a seal round the edge, the trap comes with it.
Then you simply take a bottle brush or something a bit fatter (there is
a 5cm gap round the outside for this purpose) and clean both sides of
the heat exchanger.

I'm envisioning the heat exchanger coil being fairly close wrapped, with
perhaps 5mm gaps between pipes.

Inside the top of the inspection chamber are a couple of lever valves,
to enable the coil to be bypassed, allowing it to be washed with very
hot water.


ahhhh, comprendi.

May I suggest a tweak: something closer to 6" high and nice and wide,
so you get plenty of coil in there, and lots of surface area. And so
the bath isnt half way up the wall


NT

wrote:
Ian Stirling wrote:
wrote:
Ian Stirling wrote:
snip
snip
I'm a little unclear about your diagram, so I might have misinterpreted
it, but its starting to look complex to construct and hard to get to
the muck storage to clean it. It seems theres no free lunch.

Hokay. Bigger diagram.



Shower floor. Removable plug
snip
ahhhh, comprendi.

May I suggest a tweak: something closer to 6" high and nice and wide,
so you get plenty of coil in there, and lots of surface area. And so
the bath isnt half way up the wall

I'm not sure.
At some point, as you increase in diameter for a given flow, the curtain
of falling water is going to be harder and harder to get even, perhaps
even leaving bits of pipe 'dry'.
Then there is the issue of as you decrease the number of pipes a given
bit of water flows past, you increase the temperature drop from one pipe
to the next bit down, meaning that heat transfer has to be much more
rapid.
I _think_ that for a given flow of water, thin and long is better than
short and wide. I've got to do some simple simulations though.

Ian Stirling wrote:
wrote:

May I suggest a tweak: something closer to 6" high and nice and wide,
so you get plenty of coil in there, and lots of surface area. And so
the bath isnt half way up the wall

I'm not sure.
At some point, as you increase in diameter for a given flow, the curtain
of falling water is going to be harder and harder to get even, perhaps
even leaving bits of pipe 'dry'.

true. I expect in practice it would snake about, but theres no g'tee.


Then there is the issue of as you decrease the number of pipes a given
bit of water flows past, you increase the temperature drop from one pipe
to the next bit down, meaning that heat transfer has to be much more
rapid.

erm... with wider dia, less volume of water flows per second over each
degree of the pipe pancake. It also flows less distance from top to
bottom. I think it balances out ok.

I _think_ that for a given flow of water, thin and long is better than
short and wide. I've got to do some simple simulations though.

maybe, but I dont think this is the decider. Having the bath on the
floor is more important imho than a slight thermal difference.


NT

wrote:
Ian Stirling wrote:
wrote:

May I suggest a tweak: something closer to 6" high and nice and wide,
so you get plenty of coil in there, and lots of surface area. And so
the bath isnt half way up the wall

I'm not sure.
At some point, as you increase in diameter for a given flow, the curtain
of falling water is going to be harder and harder to get even, perhaps
even leaving bits of pipe 'dry'.
snip
maybe, but I dont think this is the decider. Having the bath on the
floor is more important imho than a slight thermal difference.

I'm unsure - anyway, where are the breakpoints?
How much more efficient is 4 turns than 2, ...