Plumbing Question

Hot water booster pump and water temperature.


I have a hot water booster pump at the exit of my boiler (which is at almost ground level), and I can't regulate the temperature in the tap.

I normally open the hot water tap until the water gets hot, and then start slowly opening the cold water tap, but it's almost impossible to achieve any regulation because at a certain point the hot water stops flowing and all I get is cold water.

Opening the hot water more doesn't work, and if I turn down the cold water rapidly enough, nothing comes out of the tap until the hot water pump starts running again.

I can see that there is a pressure mismatch that causes this, but I have no idea how to fix it.

Would installing another type (and probably newer since I'm not sure the tap is appropriate for that installation) of shower mixer solve this issue?
Is this something that can be tuned in the booster pump? Or maybe some flow restriction on the cold water feed?

To be honest I'm also looking into installing a new mixer in the shower, but would want to fix this issue first and then think about investing in another tap. So maybe whoever can fix the water temperature problem can install the new mixer.

Any help is much appreciated.

Best regards,

3 Answers

Best Answer

As I understand you said "boiler" and think about hot water cylinder.

Anyway it looks as the cold pressure stops hot water in the mixer, so the pump is going off.
I will recommend a PRV (pressure reducing valve) to be installed on cold feed. Also non return valve on hot water but need to be check if not restrict much flow. PRV is necessary, non return as additional.
PRV cost is from £20-£60, fitting depend of access for cold pipe, but nothing fancy to do.
Hope will help.

Answered 27th Jan 2012

Provini Trades

Member since 10 Mar 2010

this can be solved relatively simply by installing a pressure reducing valve on the cold water mains pipe ( assuming the pressure difference is caused by this ) and then dialling down the pressure to match that of the hot water maintained pressured when being pumped.the higher pressure cold water is what is affecting the operation of the pump.

Answered 27th Jan 2012

Ardas Plumbing

Member since 27 Jan 2012

Hi , first and cheapest job would be to fit a non return valve on your cold pipe as close to the shower as poss , this might eliminate the cross mixing of the two feeds , of course changing the shower valve would prob fix this , but try this first as it a lot cheaper than a new shower valve , regards rob

Answered 27th Jan 2012

Robert Dent Heating & Plumbing

Member since 23 Jan 2012

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