Warm Water in Cold Cistern!!!

[MON5TER]

Hi

I have a gravity fed hot water cylinder. The cold cistern is in the loft and has a 22mm pipe serving the cylinder.

I have warm water in the loft cistern and its discharging from the overflow!!

I think I might know whats wrong but I would be grateful of some advice!

I have recently installed a new mixer tap shower unit. The cold supply is direct mains fed, the hot is gravity fed. I have installed a single impellar pump to boost the hot system and fed this and the cold mains through a presssure equalisation valve just before the mixer tap. One of these: http://www.plumbworld.co.uk/-230

What I think may be happening is that the mains cold pressure is pushing back down the hot supply via the eq. valve. This in turn is pushing hot water back to the cyliner and back up the supply pipe into the cistern.

Does this sound probable and if it is, what on earth do I do about it???

The mixer tap is not thermostatic which is why I put in the equalisation valve. It all seemed to work fine....

Is there a problem with the eq. valve in that it should act as a none return/check valve to the supply with the lowest pressure?

Is there some sort of additional none return/check valve I can fit to the hot supply just after the pump but before the eq valve? Something like this http://www.plumbworld.co.uk/344-1881

Or is the eq. valve just not for this purpose???

I seem to have spent hours under the bath and thought I had it sorted.

Any help would be very gratefully received.

Many thanks.

 

[Rob]

yes you need to fit a check valve on the hot pipework just before the shower.

 

[MON5TER]

Hi Rob884

Do you mean after the eq. valve and before the shower or before the eq valve?

I suspect the former as it seems to be the valve that is at fault?

Anyone know whether I have a faulty valve? Seems odd that it should do this considering the purpose of the product...?

Many thanks.

 

[Rob]

Id imagine it only equals the working pressures i.e when its being drawn.

When the water is static then the mains is obviously greater.

Just fit the check valve as close as you can to the actual shower unit.

 

[uknokianut]

you could fit a non return valve on the outlet of the hot water cylinder , that way - no water will go back up to the tank via the cold feed . Also if you fit any other mixers on the system this will solve any further problems.

 

[MON5TER]

Id imagine it only equals the working pressures i.e when its being drawn.

When the water is static then the mains is obviously greater.

Just fit the check valve as close as you can to the actual shower unit.

Sorry to question your recommendation but I just want to be sure I get it right....

If the pressurised cold is going into the eq. valve and passing across the valve and back down the hot supply pipe, if the check valve is fitted after the eq. valve and right by the mixer taps, surely it will have no effect?

It seems that the cold is getting into the hot within the body of the eq valve. There are 100mm pieces of copper pipe and a short flexible tap connector on the output side of the eq. valve serving the hot and cold sides of the taps. There is nothing else to allow hot to pass over to cold apart from within the mixer but when the valves on this are shut I don't think there is any water getting into the body of the mixer unit.

Would it not be better to put it on the hot supply just before the eq. valve?

Thanks for all your suggestions so far

uknokianut, sounds good in principle but there is difficult access to the cylinder pipework as its cleverly been built into a cupboard by the previous owners. It'll be much easier to fit under the bath and I don't intend to fit any other mixers.

Also if someone else is drawing hot it will be compromised by the mains cold flowing back down the pipes!

It still seems strange to me that the eq. valve should allow this to happen unless it is normal proctice to install with a check valve? There is a full installation diagram in the box and it is not mentioned.

 

[uknokianut]

hi - yes cut the NRV into the hot supply before the eq valve

 

[MON5TER]

Any views on whether the eq. valve is faulty and should be replaced or go with the check valve?

Which of these would be suitable?

No1: http://www.plumbworld.co.uk/344-1881

No2: http://www.plumbworld.co.uk/344-1884

Thanks again for all the help.

 

[masona]

Isn't it best take the cold feed from the cold water storage tank for the same equal correct pressure?

 

[MON5TER]

Isn't it best take the cold feed from the cold water storage tank for the same equal correct pressure?

Masona, it would be ideal and then I could fit a twin impellar booster but i couldn't get a supply from the cistern to the taps without major disruption and messing up existing decoration and flooring.

What I hoped would be a fairly simple job has turned in to a right royal pain in the ass!!

Still don't know whether the pressure eq. valve is faulty though.

Anyone???

 

[donametchi]

is the high temp stat on the boiler working properly?is the boiler constantly running?