Power shower goes cold in winter


Postby beardo » Mon Dec 14, 2009 4:33 pm

Hot water cylinder in airing cupboard.
Cold water tank in loft.

Shower pump feeding power shower.

During the summer months the system works fine. I get fantastic pressure and superb water temperature. If anything it's a little too good and I have to turn the temperature down a lot - but this is a nice problem to have.

As soon as the outside temperature drops to maybe sub 5 degress C, the shower performance becomes erratic to say the least. Sometimes it works well enough to have a decnet shower but mostly, it's icy cold interspersed with moments of warmth. If I turn the shower off and then on, it's warm again but quickly goes cold.

If I turn the temperature right up on the shower control the temperature increases to scalding point but the water pressure drops to a dribble.

Any ideas?

The only other possible symptom that I experience which may not be related is that, is if I switch off a hot tap very quickly the shower pump kicks in with an intermittent whirring until I run a tap again.
beardo
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Postby rosebery » Mon Dec 14, 2009 11:38 pm

It doesn't sound as though its piped properly at all. The clue is the taps para at the end. The shower should have totally separate hot and cold feeds from other taps etc.

Can you give a better wordpicture of how it is piped please.

Cheers
rosebery
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Joined: Wed Sep 26, 2007 8:55 pm


Postby plumbbob » Mon Dec 14, 2009 11:47 pm

Are you sure this is a proper power shower and not simply an electric shower with a pumped cold supply????
plumbbob
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Postby beardo » Tue Dec 15, 2009 4:40 pm

[quote="rosebery"]It doesn't sound as though its piped properly at all. The clue is the taps para at the end. The shower should have totally separate hot and cold feeds from other taps etc.

Can you give a better wordpicture of how it is piped please.

Cheers[/quote]

I hope this helps a little. I apologise in advance for my lack of plumbing / heating knowledge.

Watermill SS45DLV pump
2x Showerforce Riva Mixer Shower (they are never used at the same time) - 1 in each bathroom.

The pump is located on the floor of the airong cupboard, next to the hot water cylinder.
There looks to be a cold water feed from the loft going into one side of the pump and a feed from the HWC going into the other side.

Both feeds have stop cocks on them.

There are two outlets from the pump that disappear up into the loft. I don't know, at the moment what happens to those further down the pipe run.

According to the shower installation instructions there should be separate hot and cold feeds connected to the mixer, but I can't confirm that this was actually done.

One of my first thoughts about this problem was to do with water density. It makes sense (to me) that the colder the water gets, the denser it gets, and therefore with the extra 10ft of gravity supplied power is overpowering the hot water pumped from the HWC. Does this make sense to you? I was wondering if the pump was shot but it's summertime performance is great.
beardo
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Joined: Mon Dec 14, 2009 4:19 pm


Postby beardo » Tue Dec 15, 2009 4:41 pm

[quote="plumbbob"]Are you sure this is a proper power shower and not simply an electric shower with a pumped cold supply????[/quote]

I'm as sure as I can be.

It's a Showerforce Riva Mixer Shower with a Watermill SS45DLV pump.
beardo
Posts: 5
Joined: Mon Dec 14, 2009 4:19 pm


Postby rosebery » Wed Dec 16, 2009 12:12 am

"I hope this helps a little. I apologise in advance for my lack of plumbing / heating knowledge."

Everything bit of data helps. Don't be sorry.

"There looks to be a cold water feed from the loft going into one side of the pump and a feed from the HWC going into the other side."

Trace the cold feed up into the loft and ensure that it IS separately connected to the CWST from the other services. Whilst you are up there have a look at the pipes that "disappear up into the loft". They will be taking the output from the pump to each shower. Are they lagged?

PlEase describe the pipework between the HW cylinder and the pump. Is the hot teed off the vertical pipe at the top of the cylinder that takes hot to the taps or is it fed by a second pipe that apears to come out of the flange on the tp of the cylinder or is it fed by a second pipe coming out of the side of the cylinder?


"According to the shower installation instructions there should be separate hot and cold feeds connected to the mixer, but I can't confirm that this was actually done."

Absolutely correct - that is what the above is trying to check.


"Therefore with the extra 10ft of gravity supplied power is overpowering the hot water pumped from the HWC. Does this make sense to you?"

Sorry but no it doesn't I'm afriad. You do not actually have a static head difference between hot and cold at all. The HWC is replenished by a pipe which runs from the CWST and feeds cold into the bottom of the tank as hot is drawn off. So the static head for hot and cold at the pump is almost exactly the same. They are only mixed at the shower valve.


"I was wondering if the pump was shot .......... "

So was I initially - how old is it?


"........... but it's summertime performance is great."

Thats the 64k question and one which my overworked liitle excuse for a brain is having difficulty getting around at this time of night.

Cheers
rosebery
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Joined: Wed Sep 26, 2007 8:55 pm


Postby beardo » Fri Jan 15, 2010 8:47 pm

Apologies for not replying sooner. I've been otherwise engaged for the last month or so.

I hope you don't mind but I'm including a link to some photo's of the pipework in the hope that they speak a thousand words.

Google "picasaweb.google.com/Douvre/Shower?feat=directlink"


"Trace the cold feed up into the loft and ensure that it IS separately connected to the CWST from the other services. Whilst you are up there have a look at the pipes that "disappear up into the loft". They will be taking the output from the pump to each shower. Are they lagged?"

They've got the foam type insulation on them, so yes but I'm not sure how good it is. I can confirm that the cold feed is separate from the other services.

"PlEase describe the pipework between the HW cylinder and the pump. Is the hot teed off the vertical pipe at the top of the cylinder that takes hot to the taps or is it fed by a second pipe that apears to come out of the flange on the tp of the cylinder or is it fed by a second pipe coming out of the side of the cylinder?"

Photo on the link.


"So was I initially - how old is it?"

Not sure. I've been in this house for 6 years and I inherited the pump with it, and yes it's always been bad. Embarassing how long I've left it for.

Appreciate all the advice.
beardo
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Joined: Mon Dec 14, 2009 4:19 pm


Postby plumbbob » Sat Jan 16, 2010 11:13 pm

I think one possibility that needs crossing off the list is that any inline filters are partially blocked. This would make sense because in the winter the cold supply from the header tank is colder so more hot water is required in the mix to reach the required temperature.

A restricted hot flow would be evident as poor flow when the shower temperature is turned up to full hot - a symptom you mentioned.

Filter strainers are usually situated in the pump inlets and/or in the legs of the shower valve.

You are sure all the isolating valves are definitely fully open?

Does the pump note change when the shower temperature is changed to hotter and the shower becomes erratic?? It could be that the increase in demand for hot water is causing air to be drawn in causing an airlock.
plumbbob
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Joined: Wed May 07, 2008 9:59 pm


Postby beardo » Mon Jan 25, 2010 8:49 am

Hi Plumbob

"I think one possibility that needs crossing off the list is that any inline filters are partially blocked. This would make sense because in the winter the cold supply from the header tank is colder so more hot water is required in the mix to reach the required temperature."

This is also my suspicion. I guess the limescale has taken it's toll.

"Filter strainers are usually situated in the pump inlets and/or in the legs of the shower valve."

So, is this something that can be replaced or is it a case of replacing the pump?

"You are sure all the isolating valves are definitely fully open?"

Yes.

"Does the pump note change when the shower temperature is changed to hotter and the shower becomes erratic?? "

It certainly does. It's not a particularly quiet pump anyway but it does go quite high pitched and sounds like it's struggling.

Many thanks
beardo
Posts: 5
Joined: Mon Dec 14, 2009 4:19 pm


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doctor
Posts: 4
Joined: Tue Jan 19, 2010 10:30 am


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