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View the thread, titled "Basin Mixer with Mains Cold and Gravity Fed Hot" which is posted in UK Plumbers Forums on UK Plumbers Forums.

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crawf94

Hi Guys,

I’m new to the forum and looking for a bit of advice, so please take it easy on me.

I want to fit a mixer tap to a new bathroom basin, but I have mains fed cold water and gravity fed hot water. Providing I get a mixer tap suitable for low pressure will I get a decent performance from the tap. I’m concerned that as the cold pressure is much higher I will need to have the tap on full hot before I get any hot water. Would a two lever mixer tap be better for unbalanced pressures, or should I be sticking to two separate taps?

I know I could run a cold feed from the tank in the loft, but I would rather have mains cold for cleaning my teeth.

Would I need to fit check valves to both hot and cold supplies, and if so are single check valves OK are should they be double? Finally, if the pressure of the hot supply is 0.2bar how much reduction in pressure/flow would I see as a result of any check valve.

Thanks
 
The cold will overpower the Hot at the mixer.
You will need to fit a Pressure regulating valve on the cold to reduce the pressure.
If you reduce it to the same pressure as the hot, you woudn't need a Check valve, but if the cold pressure is higher you will.
 
You could buy a mixer tap that keeps the hot and cold waters separate until they leave the spout.
 
The cold will overpower the Hot at the mixer.
You will need to fit a Pressure regulating valve on the cold to reduce the pressure.
If you reduce it to the same pressure as the hot, you woudn't need a Check valve, but if the cold pressure is higher you will.

Thanks for the advice. The pressure regulating valves that I have seen have an operating output range around 1.5 - 6 bar. If 1.5 bar is the lowest I could get the pressure down to, would this still overpower the hot water at the mixer?
 
You could buy a mixer tap that keeps the hot and cold waters separate until they leave the spout.
I've tried looking for dual flow basin mixers, but there aren't that many around. There's plenty of kitchen mixers but not many basin ones. The only ones I can find are rather old fashioned and I was looking for something more contemporary looking. Anyone got any ideas where I may find one?
 
You could buy a mixer tap that keeps the hot and cold waters separate until they leave the spout.

That is the way to go. They have separate levers / heads for hot and cold and you need to ensure the taps is suitable for unbalanced systems and the pressures you have. A flow limiter in the supply pipework will help.

A single lever mixer tap is unsuitable

Don't worry too much about mixing the hot and cold together as it won't work properly due to pressure differences. Just mix the hot and cold in the basin as you would with separate taps.
 
If you've not sorted yourself yet have a look on the Pegler site ((Doncaster)) had a job last November that needed Dual Flow mono bloc basin. They fitted the bill and quite modern looking lever action stubby handles.
 
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