Shower pump problem All aspects of plumbing questions and answers, help, tips and information

[need help]

I have a thermostatic shower in my main bathroom which operates from a pump just above in the attic. The problem is that it loses good pressure within 5-10 seconds or sometimes it starts off with poor pressure. During those initial seconds the pressure is great, no problems. I think I can hear the pump in the attic almost "gasping" like if its taking in air or something at times. Can anyone give me ahint about what might be happening here and how to sort it?

[Dave From Leeds]

Where is the pump fed from? Is it from a cold water storage tank in the attic? If so it may be that the tank isn't filling properly. Check out the ball valve.

[need help]

yes cold water from a storage tank in the attic. Hot water from the immersion. When I looked it didnt seem that there was any problem with the tank filling up. There is lime in the cold tank though.

[Dave From Leeds]

If your pump has a small bleed off at the top like a radiator bleed valve, try opening it (when the shower is off) to see if any air is trapped in the pump body. Another thing to try is to get someone to turn on the shower whilst you observe the cold water tank. See if any air bubbles appear from the bottom of the tank when the shower pressure dies. This could also indicate air in the pump. This is the sort of logical step by step approach that I normally take with problems, eliminating one possible cause at a time before admitting defeat and calling on someone more knowledgeable.

[plumbbob]

Where exactly does the shower draw the water off the hot water system? It is possible when the pump starts it is drawing air down the expansion pipe causing the loss of pressure you describe.

To test, get someone in the loft to cover the vent pipe with their thumb and start the pump running. Does it now work? Is the thumb being sucked onto the pipe?