Bristan shower sometimes cold

21 Apr 2010
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United Kingdom

I have a Bristan Pisa shower with a pump on it. Sometimes when I turn it on the water doesn't get hot so after a while I turn if off again and on the second or third time it does. When it doesn't come on warm sometimes the pump gives a little squeal but nothing changes. When the shower does start up warm I think the pump sounds quieter. Sometimes I have no problems at all.

What I am wondering is if I should be looking at the pump or the thermostatic cartridge? The temperature control knob has a bit of play on it by which I mean that it doesn't move the valve when you first start moving the knob. It also moves by itself sometimes a short way from the set position.

I have taken out the cartridge and it seems ok but I am not really sure what I should be looking for.

New cartridges seem to be expensive so I don't want to replace it unnecessarily!

Does anyone have any ideas as to what could cause this intermittent hot problem ?

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A problem such as this could indicate and problem with either the pump or the shower itself.

My advise at this point is to start at the shower, as this will remove it from the list of problems so to say.

With these Bristan showers the cartridges have an internal thermostat which can stick, it is this thermostat piston which causes most temperature problems on older un-serviced units.

I would suggested removing and stripping the cartridge down, when the cartridge comes out it looks like a solid brass lump, this is the not the case.

If you look at the cartridge there is two sections for a spanners (indicated by flat areas) from memory they are just behind the first seal (long spindle end) and after the third seal (short spindle end) if you put your spanner on so they are either side of the cartridge it should unscrew in the middle, once unscrewed pull out the piston.

Once out, clean and grease the o-ring and put it back in, job done, this should restore the showers operation.

If this is doesn't I would start looking at the pump.

It might be worth finding out who makes the pump and talk to them, as pumps are generally the same but manufactures tend to vary some parts so advice can get lean as I've dealt with all pumps yet.
Thanks for the advice, I will have a closer look at the cartridge. I didn't realise it came apart any further !
Well it took a while but after taking apart the shower again the thermal control did look a bit dodgy so I decided to get a new cartridge. Then when it arrived I spent about a week looking for some silicone grease (got it from Maplins). Finally I now have it in and so far I haven't had a cold shower. The power seems much better too. All I need now is a small allen key to tighten up the temperature control knob. I just don't seem to have one the right size. One day it will all be finished.
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For anyone who has this problem and who is looking for an answer, I went through all this including getting a new cartdidge. However when it happened again all I did was to clean up the outside of the part of the cartridge and grease it ( get this from your plumbers) and it works a treat.

If you are having problems getting the cartridge out, as the nut is very thin, get yourself a 30mm box spanner from E-Bay

Yes it is a design faullt but easy to fix.

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