I've recently fitted a power shower for a friend (I know, I should have
run a mile...)

It's one of those all in one wall mount showers that basically takes tank
pressure hot and cold feeds and pumps them to the head, with a non-
thermostatic mixer. Sort of like the separate pump and mixer type, but
all in one box over the bath. It was a replacement for an existing one of
the same type but different make.

However... although it appears to work at first, it won't go hotter than
lukewarm even though the hot feed is *hot*.

After talking to the Creda techies, it loks like it's quite sensitive to
(a) flow and (b) balanced pressure on the hot and cold feeds.

The cold is a 22mm feed from the header tank then a 15mm drop inside the
wall to the shower. The hot is a 22mm feed from the top of the cylinder,
down under the floor then along to the head of the bath, then a 15mm feed
back from there along the bath and up the wall to the shower - obviously
losing a noticeable amount of pressure on the way compared to the cold.

I was thinking that to put this right, I'll need to run a more direct
feed from the top take off of the cylinder direct to the shower.
Unfortunately the cylinder is in a cupboard across the landing from the
bathroom, so a level pipe run is impossible.

If I run 22mm up to the loft and across, then drop 15mm to the shower,
that will be almost exactly the same path as the cold takes. *Except* for
the lift from the tank to the loft.

Before I start hacking it all about to do that, I thought I'd check with
you lot whether you think that will work?

PCPaul wrote:

Before I start hacking it all about to do that, I thought I'd check with
you lot whether you think that will work?

Have you tried throttling back the cold feed rate a little by turning
down its isolation valve? i.e. drop the dynamic pressure to the cold a tad.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 16 May, 18:43, John Rumm wrote:
PCPaul wrote:
Before I start hacking it all about to do that, I thought I'd check with
you lot whether you think that will work?

Have you tried throttling back the cold feed rate a little by turning
down its isolation valve? i.e. drop the dynamic pressure to the cold a tad.

--
Cheers,

John.

/================================================== ===============\
| * * * * *Internode Ltd - *http://www.internode.co.uk* * * * * *|
|-----------------------------------------------------------------|
| * * * *John Rumm - john(at)internode(dot)co(dot)uk * * * * * * *|
\================================================= ================/

Backing up John's comment, try running it with hot only - ie turn of
cold isolator - and then the other way round and see if there is a
pressure feed problem. How long does it take to fill a 5 litre
bucket, etc.?

Rob

On Sat, 16 May 2009 18:43:14 +0100, John Rumm wrote:

PCPaul wrote:

Before I start hacking it all about to do that, I thought I'd check
with you lot whether you think that will work?

Have you tried throttling back the cold feed rate a little by turning
down its isolation valve? i.e. drop the dynamic pressure to the cold a
tad.

Yes I did - but it had to be almost down to off before it made much
difference, at which point the pump started to starve..

Both feeds have the usual ball type isolating valves on them as well -I
was wondering how much restriction they put on compared to full bore
lever valves - between that and replacing speedfit plastic pipes with
copper, could that make a significant difference?

"PCPaul" wrote in message
m...
On Sat, 16 May 2009 18:43:14 +0100, John Rumm wrote:

PCPaul wrote:

Before I start hacking it all about to do that, I thought I'd check
with you lot whether you think that will work?

Have you tried throttling back the cold feed rate a little by turning
down its isolation valve? i.e. drop the dynamic pressure to the cold a
tad.

Yes I did - but it had to be almost down to off before it made much
difference, at which point the pump started to starve..

Both feeds have the usual ball type isolating valves on them as well -I
was wondering how much restriction they put on compared to full bore
lever valves - between that and replacing speedfit plastic pipes with
copper, could that make a significant difference?


I have a similar unit though mine is Showerforce and under the main control
knob is a moveable stop that you can set so as to restrict the lever
movement towards the hot side in doing that restricts the hot water in.
Worth a check
Trevor Smith

PCPaul wrote:
On Sat, 16 May 2009 18:43:14 +0100, John Rumm wrote:

PCPaul wrote:

Before I start hacking it all about to do that, I thought I'd check
with you lot whether you think that will work?

Have you tried throttling back the cold feed rate a little by turning
down its isolation valve? i.e. drop the dynamic pressure to the cold
a tad.

Yes I did - but it had to be almost down to off before it made much
difference, at which point the pump started to starve..

Both feeds have the usual ball type isolating valves on them as well
-I was wondering how much restriction they put on compared to full
bore lever valves - between that and replacing speedfit plastic pipes
with copper, could that make a significant difference?

PCPaul wrote:


Both feeds have the usual ball type isolating valves on them as well
-I was wondering how much restriction they put on compared to full
bore lever valves - between that and replacing speedfit plastic pipes
with copper, could that make a significant difference?

For a power shower I would have thought that you'd really want full bore
valves. Trying to suck through your standard "cheapie" ball valve is bound
to mess with the output.

Tim

"PCPaul" wrote in message
om...
I've recently fitted a power shower for a friend (I know, I should have
run a mile...)

It's one of those all in one wall mount showers that basically takes tank
pressure hot and cold feeds and pumps them to the head, with a non-
thermostatic mixer. Sort of like the separate pump and mixer type, but
all in one box over the bath. It was a replacement for an existing one of
the same type but different make.

However... although it appears to work at first, it won't go hotter than
lukewarm even though the hot feed is *hot*.

After talking to the Creda techies, it loks like it's quite sensitive to
(a) flow and (b) balanced pressure on the hot and cold feeds.

The cold is a 22mm feed from the header tank then a 15mm drop inside the
wall to the shower. The hot is a 22mm feed from the top of the cylinder,

If you have not taken the hot feed off the top of the cylinder strictly
in accordance with the manufactures fitting instructions then it is very
likely that not enough water is being drawn into the pump due to
sucking air fron the open vent.

Fitting a Surrey or an Essex flange can usually be an answer to this
problem.

down under the floor then along to the head of the bath, then a 15mm feed
back from there along the bath and up the wall to the shower - obviously
losing a noticeable amount of pressure on the way compared to the cold.

I was thinking that to put this right, I'll need to run a more direct
feed from the top take off of the cylinder direct to the shower.
Unfortunately the cylinder is in a cupboard across the landing from the
bathroom, so a level pipe run is impossible.

If I run 22mm up to the loft and across, then drop 15mm to the shower,
that will be almost exactly the same path as the cold takes. *Except* for
the lift from the tank to the loft.

Before I start hacking it all about to do that, I thought I'd check with
you lot whether you think that will work?

On Sun, 17 May 2009 14:38:17 +0100, Heliotrope Smith wrote:

If you have not taken the hot feed off the top of the cylinder strictly
in accordance with the manufactures fitting instructions then it is
very likely that not enough water is being drawn into the pump due to
sucking air fron the open vent.

Fitting a Surrey or an Essex flange can usually be an answer to this
problem.

It isn't, like I said it's from the hot bath tap. *But* the previous
shower which was the same type did work successfully, so I thought I had
a chance. Wrong.

Fitting a Surrey or an Essex flange can usually be an answer to this
problem.

Can I tee off the 22mm pipe already coming from the top of the tank for
the DHW supply? I suppose the main point I need an answer to is: can I
tee off there, go straight up to the loft (but staying below the bottom
of the cold header tank), then across and down to the shower?

Will there be enough pressure in the system to get the hot flowing up and
over successfully, or does it lose it in going over the top? Will the
pump pull hot through, or will it just create a vacuum and starve the
pump?

On Sun, 17 May 2009 13:34:53 +0100, Tim Downie wrote:

PCPaul wrote:


Both feeds have the usual ball type isolating valves on them as well -I
was wondering how much restriction they put on compared to full bore
lever valves - between that and replacing speedfit plastic pipes with
copper, could that make a significant difference?

For a power shower I would have thought that you'd really want full bore
valves. Trying to suck through your standard "cheapie" ball valve is
bound to mess with the output.

They only cost a pound or so more - why do people use the cheapie type at
all?

How about speedfit plastic pipes - are they much worse than copper?

"PCPaul" wrote in message
om...
On Sun, 17 May 2009 14:38:17 +0100, Heliotrope Smith wrote:

If you have not taken the hot feed off the top of the cylinder strictly
in accordance with the manufactures fitting instructions then it is
very likely that not enough water is being drawn into the pump due to
sucking air fron the open vent.

Fitting a Surrey or an Essex flange can usually be an answer to this
problem.

It isn't, like I said it's from the hot bath tap. *But* the previous
shower which was the same type did work successfully, so I thought I had
a chance. Wrong.
OK I re-read your original post and though it does'nt mention the hot tap it
does seem to infer it

Fitting a Surrey or an Essex flange can usually be an answer to this
problem.

Can I tee off the 22mm pipe already coming from the top of the tank for
the DHW supply? I suppose the main point I need an answer to is: can I
tee off there, go straight up to the loft (but staying below the bottom
of the cold header tank), then across and down to the shower?

The manufactuers fitting instructions probably prefer Surrey or Essex flange
fitting. However, they may show diagrams of pipework configuations and
indicate how and where these can be connected to.
If you cannot connect as shown it is likely to be a waste of time.

Will there be enough pressure in the system to get the hot flowing up and
over successfully, or does it lose it in going over the top? Will the
pump pull hot through, or will it just create a vacuum and starve the
pump?

As long as the pipework runs at a lower level than the cold storage tank
then there should be no problem.

Heliotrope Smith wrote:

Can I tee off the 22mm pipe already coming from the top of the tank for
the DHW supply? I suppose the main point I need an answer to is: can I
tee off there, go straight up to the loft (but staying below the bottom
of the cold header tank), then across and down to the shower?

The manufactuers fitting instructions probably prefer Surrey or Essex flange
fitting. However, they may show diagrams of pipework configuations and
indicate how and where these can be connected to.
If you cannot connect as shown it is likely to be a waste of time.

Some of this will depend on how much power the pump has. Some of these
"all in one" wall mounting jobbies are fairly low pressure anyway and
often work in quite "non optimal" configurations - but only deliver
underwhelming results when working.

The more powerful the pump the more important the "correct" plumbing
becomes.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sun, 17 May 2009 23:59:38 +0100, John Rumm wrote:

Some of this will depend on how much power the pump has. Some of these
"all in one" wall mounting jobbies are fairly low pressure anyway and
often work in quite "non optimal" configurations - but only deliver
underwhelming results when working.

The more powerful the pump the more important the "correct" plumbing
becomes.

I'm expecting this to be only 'adequate' - I like a can-only-barely-stand-
up-under-it shower myself, but this isn't for me.

I gather from Creda that matching the input pressures is more important
for it to work satisfactorily than anything else, so that's what I'm
mostly fussed about.