Pulsating shower

[Ezra]

New here and have browsed to try to find a problem similar to mine. If I have missed it, I apologise.

I have had a mixer shower fitted to an extension. Gravity system. 2 bar cold. 0.2 bar hot. shower on same level as large hot water cylinder. Large water tank in attic, 4.5 metres from hot water tank.

Mixer is minimum running water pressure 0.1 bar but optimum at 0.5 bar. Maximum running water pressure 5 bar.

The problem is the shower will most often pulsate when running (1-2 pulses a second). If I adjust the temp to full HOT it will stop; if I adjust the temp to full COLD it will stop. If I gingerly move from the 38 degrees to hot, I can stop it pulsing.

Not sure about the hot water temp from the tank, just know it's very hot!

Any ideas abut how to resolve this? It's for my mother so it needs to be right.

Thanks
Ez

 

[HERTS P&D]

You can not have a mixed pressure supplies on a shower.

Andy

 

[Ezra]

Hi Andy,

are you suggesting the pressure variation on the hot and cold feed is the problem?

I have a mira 723 thermostatic shower in the main house and it is absolutely fine and the pressure will presumably be the same to that one????

I should add (perhaps) that I have no central heating (electric storage heaters)...

Thank you,
Ez

 

[kbdiy]

Sounds to me as though the shower stat is busy trying to compensate for the varying pressure between the 2 feeds, hence the pulsing as it tries to find the right balance. Too much pressure variation between the hot and cold I would say.

Is the cold feed direct from the mains? If so can you run a new feed direct from the cold water tank in the loft? That should give a more balanced flow.