fluctuating water flow on mixer shower

[lostcause1798]

I’ve just had a mixer shower fitted, taking hot water from a Combi boiler.

When I turn on the shower the water flow is constant but as it heats up and once it’s warm the flow of water starts to fluctuate (pump), high pressure, low pressure, high pressure, low pressure, etc, it changes every second or even less than second.

When I run hot water in the kitchen or in bathroom bath or sink then the water flow appears constant.

Ay ideas what could be causing this / how to fix it?

Thanks.

 

[Agile]

You dont tell us the make and model of boiler!

As a start turn down the hot water temperature control on the boiler.

The boiler and shower are interacting with each other.

Why have you not complained to your shower installer and got him to sort it out?

Tony

 

[lostcause1798]

sorry - it's a Worcester 28i boiler.

The plumber that fitted it has got a job in another part of the country and is no longer around (i got it fitted a month ago - but have only fully checked it now)

The boiler is approx 2 years old, and prior to getting this shower fitted there was no shower running from it. It was just running radiators and hot water taps.

Would running the shower, with the shower head below the mixer tap cause any problems? It's not permanently like this, it's just I was holding the shower head in my hand when I checked it.

Thanks.

 

[Agile]

As a start turn down the hot water temperature control on the boiler.

Tony

 

[lostcause1798]

The boiler was actually already at the 'summer' setting and so is as low as it can go.

I did try it at a higher setting but the same thing happened.

Once the water becomes hot, the water starts to 'pulse'.

 

[kier]

which shower mixer do you have.

 

[lostcause1798]

The shower mixer make is Hansgrohe Marin Centostat Exposed Shower.

thanks