Shower pump starting up at random - ideas? Help!?

[Masood]

Hi all,

I'm full of questions today!

I've been to a house with 3 bathrooms:

1 is fully pumped, thermostatic basin tap, thermostatic shower mixer
2 shower only is pumped
3 shower only is pumped

The shower is a Stuart Turner one, not sure of model number, was well hidden!

The problem is that the pump kicks on at random times, running for short bursts. I've been round looking for leaks, and there are none. Also checked if any of the taps are dripping, also none.

Any ideas as to what else could be causing this? If it makes any difference, the CWSC is one floor higher than the HWSC, I was wondering if the different pressures could be causing water to flow through the circuit, maybe in conjunction with a passing thermostatic mixer, triggering the flow switch (long shot, I know!)

The pipework is atrocious - a mix of Polyplumb and JG speedfit, mostly unsupported, and no iso valves before any of the appliances, although I doubt whether that could be the cause?

The customer does say that the problem is more frequent when the house is full and bathrooms are used more frequently.

Thanks in advance!

 

[AlexGas]

Poor install, air in the pipework. Check valve could be a solution.

 

[mountainman]

Assuming that the pump is negative head then a slight overflow or leak in a wc cistern could cause this.

 

[R1CKY]

Had similar a while back. Pump would run if a hot tap (not pumped) was shut suddenly. I put it down to the sudden stop causing a "shockwave" in the hot water pipework, which was triggering the flow switch in the pump. I put a single check valve on the hot outlet from the shower pump and it solved the problem.

 

[Masood]

Assuming that the pump is negative head then a slight overflow or leak in a wc cistern could cause this.

Will check if the WC cistern is also pumped in bathroom 1. The other two aren't so can rule those out I guess...

I may just put check valves on both outlets from the pump to rule out pressure differential or mixers...

 

[BLOD]

Personally I think you're on to the right thing with the different heights for hot & cold stored water - maybe investigate that a bit more ?
Showers like a balanced supply

 

[stevetheplumber]

is the pump one where both hot and cold impellors are adjacent to each other ie on one end of the motor if yes and you have unequal pressures the seal between them will pass water had the same thing before

 

[Masood]

Steve, no - they are on opposite ends...