I'm taking a year off from renovations during 2009, but next spring I'm
planning to renovate the main bathroom on my bungalow here in sunny
Cumbria. As you probably know it gets quite cold here and I
continually plot ideas to save heating oil - I used 1000l since the
beginning of November.

The boiler is a new Mistral Condensing 50-90 unit, and I have an OSO
pressurised 210l water tank (thanks Dr.D, I know about thermal stores,
and in 20 years that'll be the way I'll go). I'll lay in lots of wall
insulation, of course, and if I can, the heating will go underfloor as
I did in the Sitting Room, with insulation under (I used 100mm in the
Sitting Room). The loft is 250mm insulated.

So it seems to me that the biggest waste of heat left in the bathroom
will be the grey-water from SWMBO's daily baths - she does not do
showers. I'm planning on a smaller bath (sssh!) But is there a simple
way of using the waste heat in the grey-water for heating (aside from
letting it go cold in the bath tub before pulling the plug)?

R.

Richard A Downing wrote:

So it seems to me that the biggest waste of heat left in the bathroom
will be the grey-water from SWMBO's daily baths - she does not do
showers. I'm planning on a smaller bath (sssh!) But is there a simple
way of using the waste heat in the grey-water for heating (aside from
letting it go cold in the bath tub before pulling the plug)?

Call me a killjoy but I think that amount of heat economically recoverable
this way in a domestic setting is minimal. You might come across the odd
enthusiast but I think you'll find most folk here will say the same.

Tim

On Wed, 11 Feb 2009 16:57:46 +0000, Richard A Downing wrote:

As you probably know it gets quite cold here and I continually plot
ideas to save heating oil - I used 1000l since the beginning of
November.

Only 1000? We've got through nearly 2000 since the end of November. Will
be due to order another 2000 in about 10 days time...

But is there a simple way of using the waste heat in the grey-water for
heating (aside from letting it go cold in the bath tub before pulling
the plug)?

Even if you can effectively recover it what are you going to do with such
"low grade" heat? Any medium you recover the heat into is only going to be
around the upper 30's C at best. Too cool even for under floor heating.

How much actual energy is there in a bath full of water? Is it worth
recovering given that it is such low grade?

--
Cheers
Dave.

In article et,
"Dave Liquorice" writes:
On Wed, 11 Feb 2009 16:57:46 +0000, Richard A Downing wrote:

As you probably know it gets quite cold here and I continually plot
ideas to save heating oil - I used 1000l since the beginning of
November.

Only 1000? We've got through nearly 2000 since the end of November. Will
be due to order another 2000 in about 10 days time...

But is there a simple way of using the waste heat in the grey-water for
heating (aside from letting it go cold in the bath tub before pulling
the plug)?

Even if you can effectively recover it what are you going to do with such
"low grade" heat? Any medium you recover the heat into is only going to be
around the upper 30's C at best. Too cool even for under floor heating.

How much actual energy is there in a bath full of water? Is it worth
recovering given that it is such low grade?

You could just leave it to cool down before pulling the plug.
That way, the heat has passed into the house. The moisture it
generates by evaporation might not be welcome though. Could
cover the top to prevent evaporation, but then it will take
much longer to cool.

If you're into DIY refrigeration, another option would be to
pump the heat from the bath back into the hot water cylinder.
You could affix evaporater pipework to the back of a (metal)
bath, and have a condenser coil in the bottom of your hot water
cylinder. Then you cool or even chill the bath water, dumping
the heat back into the hot water cylinder. Almost certainly
not worth it, but might be good fun. ;-)

I've thought about recovering the heat from a shower. That's
easier because you can just construct a reverse flow heat
exchanger to transfer the waste heat to the hot water cylinder
inlet flow, as they'd both be flowing at the same time.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

"Andrew Gabriel" wrote in message
...
In article et,
"Dave Liquorice" writes:
On Wed, 11 Feb 2009 16:57:46 +0000, Richard A Downing wrote:

As you probably know it gets quite cold here and I continually plot
ideas to save heating oil - I used 1000l since the beginning of
November.

Only 1000? We've got through nearly 2000 since the end of November. Will
be due to order another 2000 in about 10 days time...

But is there a simple way of using the waste heat in the grey-water for
heating (aside from letting it go cold in the bath tub before pulling
the plug)?

Even if you can effectively recover it what are you going to do with such
"low grade" heat? Any medium you recover the heat into is only going to
be
around the upper 30's C at best. Too cool even for under floor heating.

How much actual energy is there in a bath full of water? Is it worth
recovering given that it is such low grade?

You could just leave it to cool down before pulling the plug.
That way, the heat has passed into the house. The moisture it
generates by evaporation might not be welcome though. Could
cover the top to prevent evaporation, but then it will take
much longer to cool.

If you're into DIY refrigeration, another option would be to
pump the heat from the bath back into the hot water cylinder.
You could affix evaporater pipework to the back of a (metal)
bath, and have a condenser coil in the bottom of your hot water
cylinder. Then you cool or even chill the bath water, dumping
the heat back into the hot water cylinder. Almost certainly
not worth it, but might be good fun. ;-)

I've thought about recovering the heat from a shower. That's
easier because you can just construct a reverse flow heat
exchanger to transfer the waste heat to the hot water cylinder
inlet flow, as they'd both be flowing at the same time.

See my post on the gfx. If can be DIYed by having a pipe in pipe and reverse
flow.

On Wed, 11 Feb 2009 19:41:12 +0000 (GMT)
"Dave Liquorice" wrote:

On Wed, 11 Feb 2009 16:57:46 +0000, Richard A Downing wrote:

As you probably know it gets quite cold here and I continually plot
ideas to save heating oil - I used 1000l since the beginning of
November.

Only 1000? We've got through nearly 2000 since the end of November. Will
be due to order another 2000 in about 10 days time...

Two active young-for-our-age oldies. No kids. Few visitors. Lots of
insulation. 20 degree thermo setting. South-facing big K-glass/Argon
windows.

But is there a simple way of using the waste heat in the grey-water for
heating (aside from letting it go cold in the bath tub before pulling
the plug)?

Even if you can effectively recover it what are you going to do with such
"low grade" heat? Any medium you recover the heat into is only going to be
around the upper 30's C at best. Too cool even for under floor heating.

How much actual energy is there in a bath full of water? Is it worth
recovering given that it is such low grade?


OK, I'm convinced. Scrap that idea....

Thanks.

R.

In article , Richard A
Downing writes

But is there a simple
way of using the waste heat in the grey-water for heating (aside from
letting it go cold in the bath tub before pulling the plug)?

I've often wondered if this could be used to warm up the cold feed to a
mixer shower (or even an elcetric one). It'd need to be a thermostatic
mixer, however.

--
(\__/)
(='.'=) Bunny says Windows 7 is Vi$ta reloaded.
(")_(") http://imgs.xkcd.com/comics/windows_7.png

Mike Tomlinson coughed up some electrons that declared:

In article , Richard A
Downing writes

But is there a simple
way of using the waste heat in the grey-water for heating (aside from
letting it go cold in the bath tub before pulling the plug)?

I've often wondered if this could be used to warm up the cold feed to a
mixer shower (or even an elcetric one). It'd need to be a thermostatic
mixer, however.

http://wiki.diyfaq.org.uk/index.php?...Heat_Exchanger

In article , Tim S
writes

http://wiki.diyfaq.org.uk/index.php?...Heat_Exchanger

Thanks :-)

--
(\__/)
(='.'=) Bunny says Windows 7 is Vi$ta reloaded.
(")_(") http://imgs.xkcd.com/comics/windows_7.png

"Tim S" wrote in message
...
Mike Tomlinson coughed up some electrons that declared:

In article , Richard A
Downing writes

But is there a simple
way of using the waste heat in the grey-water for heating (aside from
letting it go cold in the bath tub before pulling the plug)?

I've often wondered if this could be used to warm up the cold feed to a
mixer shower (or even an elcetric one). It'd need to be a thermostatic
mixer, however.

http://wiki.diyfaq.org.uk/index.php?...Heat_Exchanger

Also, and this works......and tested by the US dept of energy.
http://gfxtechnology.com/faq.html

Also..I don't know much about these...
http://www.shower-save.com/

A cut from a thread in uk.d-i-y from 2006: Payback was 2 years, by a real
user.
"I cut my DHW heating by somewhere between 1/3 and 1/2 by installing a
waste-water heat-exchanger."

"daestrom" wrote in message
...

"Doctor Drivel" wrote in message
reenews.net...

"daestrom" wrote in message
...

"Derek Broughton" wrote in message
...
Ron Purvis wrote:

I think you are off on your figures. According to
http://www.fsec.ucf.edu/solar/apps/sdhw/dhwsave.htm the typical home
uses 20 gallons of hot water per day for the first two persons and 15
gallons of hot water for each additional person. That would be 25,550
gallons of hot water per year for a family of four.

OK, I'll accept those numbers. Anyone got a better figure on the
average cost of heating water? My numbers for heat required are, if
anything, on the low side, but at $25/million BTU, and only 25,000
gallons per year, you're talking $250/year (somebody else said
$20/month, so same ballpark).
Still plenty to make a commercial solar water heater pay off.

I cut my DHW heating by somewhere between 1/3 and 1/2 by installing a
waste-water heat-exchanger. Running hot water for a shower and letting
all the energy go down the drain (literally), just doesn't make sense.
Of course, this system only recovers heat from *running* water, so baths
and dish washing doesn't affect it.

I have one of the largest units and it is a two-pass type so is not the
most efficient model they have. Mine cost only about $270, did the
installation myself.

http://www.gfxtechnology.com/

What was the payback period?

I have a family of five. Even with a low-flow shower head, that works out
to about 34000 gallons of water a year. Of course it's mixed hot and cold
to create just a nice 'warm' shower of about 100F. The average year-round
water supply temp for me is 55F. So that works out to about 127 Therms of
NG a year. When I bought the thing, NG was $0.80/therm. The payback with
that 5% interest on $270 worked out to just about three years. With NG
prices running $1.30/therm, it's under 2 years. But mine has already paid
for itself.

Nice one daestrom, you obviously did your homework on payback. This company
have been threatening to setup in the UK (or have an agent) for a time.
Googling brings up some very encouraging feedback, and seems a better
investment than solar. The US government sites speak highly of it.

Unfortunately most homes here don't have basements, as they do in the USA,
so difficult to locate in a house. I see they have just brought out a batch
processing unit that can be located anywhere, so clawing back bathwater is
possible not just shower water. They use a controller and pump, so more
complicated. As my 4 year girl likes splashing about in a bath, the payback
might be a bit longer for me using the shower version.

But looks like they can be DIYed. One copper inside another, differential
controller and a pump. They work by the water spiralling around the pipes
and sticking to the sides as gravity pulls the water down. If a pump forced
water through too fast maybe it would not do this and heat wasted. Just a
thought. The pump's speed would have to be calculated.

Currently most people just would not believe they actually work.

On Feb 12, 8:02*am, Mike Tomlinson wrote:
In article , Richard A
Downing writes

But is there a simple
way of using the waste heat in the grey-water for heating (aside from
letting it go cold in the bath tub before pulling the plug)?

I've often wondered if this could be used to warm up the cold feed to a
mixer shower (or even an elcetric one). *It'd need to be a thermostatic
mixer, however.


So have I, and i think it could. A counterflow heat exchanger might
recover 80% of the heat. Yo ushoudl then be able to have a high flow
rate shower running on a small electric shower heater.

Robert

On 12 Feb, 13:04, RobertL wrote:

A counterflow heat exchanger might recover 80% of the heat. *

Does "counterflow" have any real meaning when we're talking about such
a small flow, that's so intermittent?

Andy Dingley wrote:
On 12 Feb, 13:04, RobertL wrote:

A counterflow heat exchanger might recover 80% of the heat. *

Does "counterflow" have any real meaning when we're talking about such
a small flow, that's so intermittent?

You wont get good recovery if its not counterflow.


NT

"Richard A Downing" wrote


So it seems to me that the biggest waste of heat left in the bathroom
will be the grey-water from SWMBO's daily baths - she does not do
showers. I'm planning on a smaller bath (sssh!) But is there a simple
way of using the waste heat in the grey-water for heating (aside from
letting it go cold in the bath tub before pulling the plug)?


Others seem to dismiss the heat recovery option.
It may be more energy/cost efficient to look at filtering and re-using the
grey water for toilet flushing/garden watering.
Leave you to do the maths though

Phil

TheScullster wrote:
"Richard A Downing" wrote

So it seems to me that the biggest waste of heat left in the bathroom
will be the grey-water from SWMBO's daily baths - she does not do
showers. I'm planning on a smaller bath (sssh!) But is there a simple
way of using the waste heat in the grey-water for heating (aside from
letting it go cold in the bath tub before pulling the plug)?


Others seem to dismiss the heat recovery option.
It may be more energy/cost efficient to look at filtering and re-using the
grey water for toilet flushing/garden watering.
Leave you to do the maths though

Phil

By doing that you would recover the heat, as the warm water would sit
around long enough to go cold. That would be useful 9 months of the
year.

Evaporation from leaving bathwater in situ might be countered with a
few drops of oil. What effect doing this would have on bath cleaning I
dont know.


NT

On 12 Feb, 08:52, wrote:

Evaporation from leaving bathwater in situ might be countered with a
few drops of oil. What effect doing this would have on bath cleaning I
dont know.

What a super idea.

Just let me think; why do lubricated air compressors (as against oil-
free compressors) often come complete with oleophilic and activated
charcoal filters for connection to the receiver's condensate drain?

Ah yes; that would be because it is very environmentally unfriendly
and very illegal to put oil into the drainage system.

Is there any area of technology in which you don't hold your expertise
in high regard and don't feel a compulsive need to propagate your half-
baked ideas across the internet?

Onetap wrote:
On 12 Feb, 08:52, wrote:

Evaporation from leaving bathwater in situ might be countered with a
few drops of oil. What effect doing this would have on bath cleaning I
dont know.

What a super idea.

Just let me think; why do lubricated air compressors (as against oil-
free compressors) often come complete with oleophilic and activated
charcoal filters for connection to the receiver's condensate drain?

Ah yes; that would be because it is very environmentally unfriendly
and very illegal to put oil into the drainage system.

Is there any area of technology in which you don't hold your expertise
in high regard and don't feel a compulsive need to propagate your half-
baked ideas across the internet?


Who is going to be the first to tell Johnson & Johnson?

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

Rod wrote:
Onetap wrote:
On 12 Feb, 08:52, wrote:

Evaporation from leaving bathwater in situ might be countered with a
few drops of oil. What effect doing this would have on bath cleaning I
dont know.

What a super idea.

Just let me think; why do lubricated air compressors (as against oil-
free compressors) often come complete with oleophilic and activated
charcoal filters for connection to the receiver's condensate drain?

Ah yes; that would be because it is very environmentally unfriendly
and very illegal to put oil into the drainage system.

Is there any area of technology in which you don't hold your expertise
in high regard and don't feel a compulsive need to propagate your half-
baked ideas across the internet?


Who is going to be the first to tell Johnson & Johnson?

Indeed, or the many skin cleaner and hair conditioner manufacturers
that put oil in their products. Perhaps the effect of the detergent in
the bathwater went unnoticed.

To mr onetap, I dont recall claiming to be offering an expert opinion
there. This is a discussion thread, for the purpose of discussing
possibilities.


NT

On 12 Feb, 18:42, Rod wrote:

Ah yes; that would be because it is very environmentally unfriendly
and very illegal to put oil into the drainage system.

Is there any area of technology in which you don't hold your expertise
in high regard and don't feel a compulsive need to propagate your half-
baked ideas across the internet?

Who is going to be the first to tell Johnson & Johnson?

Baby oil? Mineral oil? On a baby? Why? Do they rust?
Just hand out a COSHH data sheet with every bottle.
Is it just me that associates the phrase 'mineral oil' with the words
cancer and testicular.

In article ,
"TheScullster" writes:

"Richard A Downing" wrote


So it seems to me that the biggest waste of heat left in the bathroom
will be the grey-water from SWMBO's daily baths - she does not do
showers. I'm planning on a smaller bath (sssh!) But is there a simple
way of using the waste heat in the grey-water for heating (aside from
letting it go cold in the bath tub before pulling the plug)?


Others seem to dismiss the heat recovery option.
It may be more energy/cost efficient to look at filtering and re-using the
grey water for toilet flushing/garden watering.
Leave you to do the maths though

That's what you call a hot flush...

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Richard A Downing wrote:
I'm taking a year off from renovations during 2009, but next spring I'm
planning to renovate the main bathroom on my bungalow here in sunny
Cumbria. As you probably know it gets quite cold here and I
continually plot ideas to save heating oil - I used 1000l since the
beginning of November.

The boiler is a new Mistral Condensing 50-90 unit, and I have an OSO
pressurised 210l water tank (thanks Dr.D, I know about thermal stores,
and in 20 years that'll be the way I'll go). I'll lay in lots of wall
insulation, of course, and if I can, the heating will go underfloor as
I did in the Sitting Room, with insulation under (I used 100mm in the
Sitting Room). The loft is 250mm insulated.

So it seems to me that the biggest waste of heat left in the bathroom
will be the grey-water from SWMBO's daily baths - she does not do
showers.

A quick question...

Do you have a power shower? If you do, you might be surprised at the
amount of water that can be used during a shower. I have taken to
pulling the switch cord to turn the pump off when I am soaping up and
don't need the flow of water.

Dave

On Fri, 13 Feb 2009 00:10:27 +0000, Dave
wrote:

Richard A Downing wrote:
I'm taking a year off from renovations during 2009, but next spring I'm
planning to renovate the main bathroom on my bungalow here in sunny
Cumbria. As you probably know it gets quite cold here and I
continually plot ideas to save heating oil - I used 1000l since the
beginning of November.

The boiler is a new Mistral Condensing 50-90 unit, and I have an OSO
pressurised 210l water tank (thanks Dr.D, I know about thermal stores,
and in 20 years that'll be the way I'll go). I'll lay in lots of wall
insulation, of course, and if I can, the heating will go underfloor as
I did in the Sitting Room, with insulation under (I used 100mm in the
Sitting Room). The loft is 250mm insulated.

So it seems to me that the biggest waste of heat left in the bathroom
will be the grey-water from SWMBO's daily baths - she does not do
showers.

A quick question...

Do you have a power shower? If you do, you might be surprised at the
amount of water that can be used during a shower. I have taken to
pulling the switch cord to turn the pump off when I am soaping up and
don't need the flow of water.

Go to Antarctica and you *have* to do that. 1 minute water, then
apply soap and shampoo. Then you have 1 minute to rinse off.
Fortunately they don't use combi's so that nearly all the water is at
the correct temperature.





--