Mixer shower running hot then cold

[nstewart30]

Hi there,

I have just purchased a house where there is a valiant hot water heater and a mixer shower on the bath taps.

The shower goes from scalding hot to cold very quickly. The cold water pressure is greater than the hot and my theory is that the cold is pushing the hot back on itself and causing the boiler/water heater to switch off.

Would putting a 22mm check valve on both the hot and cold supply remedy the intermittent heat in the water?

 

[ChrisOxford]

Is your cold supply direct off the mains, and hot from a tank?

 

[BlueMoonMole]

Run your shower, walk over to your boiler and see for yourself!

Is the boiler coming on, and going off, intermittently, whilst the shower is running?

 

[nstewart30]

Is your cold supply direct off the mains, and hot from a tank?

Ironically, it's the other way around. Hot is a direct feed into the water heater and cold is from a tank in the loft.

 

[nstewart30]

Run your shower, walk over to your boiler and see for yourself!

Is the boiler coming on, and going off, intermittently, whilst the shower is running?

The boiler stays on constantly when I change the setting on the mixer tap to taps only. It goes on and off when I put it on the shower mode. I've checked it by looking at it too.

 

[ChrisOxford]

What about when you select shower mode and hot as possible? Does the boiler still cycle on and off?

Have you checked any filters?

Do you have (or can you get) the manufacturer's instructions for the mixer?

BTW, does it have a hot tap, separate cold tap, a temperature control and a diverter to select bath or shower?

 

[nstewart30]

What about when you select shower mode and hot as possible? Does the boiler still cycle on and off?

Have you checked any filters?

Do you have (or can you get) the manufacturer's instructions for the mixer?

BTW, does it have a hot tap, separate cold tap, a temperature control and a diverter to select bath or shower?

Unfortunately, I can't get hold of the manufacturers instructions.

I have tried as hot as possible, but still have the same problem.

The mixer unit has a separate cold and hot feed, no temperature control and a knob at the centre to change it from tap to shower.