Mixer tap on a gravity fed hot water system

[ksareen]

Hi all

Just moved into a house and out of several things the wife complained about was that there were seperate taps for HOT and COLD in the bathroom sink. She wanted a MIXER instead and she gets what she wants.

The basin HOT water tap is gravity fed but the mixer shower valve is pump fed (negative head). The expansion tank (at the top), header tank (in the middle) and copper tank (at the bottom) are all in the first floor airing cupboard.

The issue I've now is that the HOT WATER pressure is much less compared to stand alone tap. The COLD WATER is as good as before but when used as a MIXER tap, the cold is actually pushing HOT WATER back and filling up the HEADER TANK (overflow fitted).

When installing the mixer basin valve, I used the flexi hoses with isolation valves built in. Can they reduce the flow rate?

Is there a way to fix this or should I go back to stand alone taps. I could put pressure reducing on COLD TAP but how to get the HOT WATER back to its original flow rate?

OR should I feed the HOT WATER from the pump.

The hot water flow rate in the kitchen sink (mixer tap) is also not very good. What I've also noticed is that the OLD ball valve in the header tank is slower to fill the header tank compared to the New ball valve in my cistern. Not sure if it matters though in this situation.

Thanks for yout help in advance..

 

[WHPES]

Don't do that. Completely unnecessary on the hot and the shower will already have integral ones present in the mixer. They are only to comply with the water regs in the event of a fault and do not have any usefeulness in normal operation.

 

[ksareen]

The reason for doing both HOT and COLD was that at the moment, when using both taps (as mixer), the cold is pushing HOT water back into the copper cylinder and into the header tank. DC valve would stop that.

But you are right. When I would install pumped HOT and equalising/ balancing valve, then I won't need DC on the HOT pipe.

Thanks once again.