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Bad hot water pressure from newly installed shower valve

Postby Ronbrownlow » Tue Dec 28, 2010 4:53 pm

We have a low pressure system where it is a lagged hot water cylinder and mains pressure cold.

The shower valve is a thermostatic mixer for use with low or high pressure systems (so say instructions) (low pressure as low as 1bar) Crosswater EV1210EC

I've taken the shower valve off and just opened the valve and it jets out fine.

I've taken the controls off the end of the shower valve and put the shower valve back on and then open the valves again and the flow is still much restricted.

I've taken out the one way valves in the shower valve and tried again, still loss of pressure is experienced.

Have I got the wrong shower valve? Any ideas?
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Postby plumbbob » Wed Dec 29, 2010 12:49 am

I would not consider one bar to be "low pressure". Generally low pressure would be described as 0.1 bar.

A shower unit working at 0.1 bar would require 1 metre head of water to work satisfactorily. ie,a metre would be required measuring between the shower head and the bottom of the header tank.

A one bar mixer would require 10x that ie, 10 metres.


Very very few showers will work with mixed pressure hot and cold feeds and those that do require special adapters fitted. You are certain this is one of those?

I avoid mixed pressure installations even if the shower will work as I have found them to be very temperamental.
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Postby jim the plumb » Fri Dec 31, 2010 12:36 pm

Your post would suggest the cold water is overpowering the hot water from the cylinder to the shower.

You haven't mentioned whether the cold supply to the shower is from the mains or the tank in the loft.

If it is mains, you need to run new pipework from the loft tank to the shower (cold in). This way the water supply will be equal.

You say it is new - did you install it?

HTH jimbo
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Postby htg engineer » Fri Dec 31, 2010 8:37 pm

The cold and hot water must be tank fed, you should not have a shower fed from hot water tank and mains cold water - if the mains cold water ever goes off - whoever is showering could be scalded.

For the shower to work properly you need both hot and cold at same pressure.

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