Non return valve- Hot water bath?!

[Deleted member 84317]

Hi

(System is header tank in loft, indirect hot water tank)

After the hot water isolation valve under my bath, there is a non return valve between the isolation valve and the hot water tap.

When I switch the hot water (mixer tap) on in the bath nothing happens until I flick the SINK mixer tap on and off and then the hot water runs in the bath (the non return valve sticks closed, till you mess with the sink mixer tap).

I have tried without a non return valve in the line but then water comes out of the overflow from the header tank in the loft, to the outside, so I have put a new non return valve back in.

Now the sink 'trick' doesn't work any more N.R Valve must me stuck closed and won't release. Clearly the N.R valve shouldn't be there.

Any ideas anyone?

Regards
Adam

 

[ShaunCorbs]

You’ve installed the nrv the correct way ?

 

[Deleted member 84317]

You’ve installed the nrv the correct way ?

The previous non plumber house owner fitted it and to be honest that could be it . Is it normal common/to have one there?

 

[ShaunCorbs]

Yes if the cold is mains fed

 

[Deleted member 84317]

Yes if the cold is mains fed

Forgive me if I'm being thick, even though this is only when I want hot water? (the nr valve is only on the hot feed pipe)

 

[snowhead]

Yes it needs to be there, you've found out what happens when it's not there.

There probably isn't sufficient pressure on the hot side to lift the spring in the NRV.

 

[Deleted member 84317]

Yes if the cold is mains fed

The flow arrow points towards the taps in the bath, wrong way??

 

[ShaunCorbs]

correct way

 

[Deleted member 84317]

correct way

Oh Have you any suggestions for my problem?

 

[JCplumb]

Oh Have you any suggestions for my problem?

Seperate hot and cold taps or a mixer that only allows the mix after the valves, the normal advice for your type of tap and water system would be to fit an NRV, if the pressure is too low to operate the NRV then new taps - unless you want to get a pump installed, but the expense and future maintenance is more costly/problematic than just getting new taps.

 

[Stu-B]

Sounds like you need new mixer tap, the cartridge has bust and it’s sending cold water up the hot pipe back filling the cylinder then up the expansion pipe, filling loft tank then out of the over flow.
Some idiot has tried a cheap fix by fitting a non return on the hot but the, pressure on the cold is greater and keeping it shut until you open the other tap.

New taps and bin the nrv


Seen it loads

 

[Chalked]

Must be a bath mixer , or is there a mixer under the bath?

 

[Millsy 82]

The correct thing to do would be to equalise the pressure by running a tank fed cold to your bath.

You could try a low pressure non return valve.

 

[Deleted member 84317]

correct way

Do you agree with installing new taps Shaun?

 

[ShaunCorbs]

Do you agree with installing new taps Shaun?

Well depends if the taps at fault can you remove the hot side cartridge

 

[Deleted member 84317]

Well depends if the taps at fault can you remove the hot side cartridge

This is the tap (photo’s). I can remove it, what do you think?

 

[Deleted member 84317]

What I mean is, does that tap have a cartridge?

 

[Darren Jackson]

You actually do need NRV's on both the hot and cold pipes as per water regs, one to stop the cold forcing its way up the hot water pipes and filling the header tank up and the other on the cold feed pipe for backflow prevention and possible cross contamination of the potable water. If you are having problems then fit a pressure reducing valve on the cold feed pipe to the tap in question to balance the feeds.

 

[Millsy 82]

You actually do need NRV's on both the hot and cold pipes as per water regs, one to stop the cold forcing its way up the hot water pipes and filling the header tank up and the other on the cold feed pipe for backflow prevention and possible cross contamination of the potable water. If you are having problems then fit a pressure reducing valve on the cold feed pipe to the tap in question to balance the feeds.

Water regs would say you would need one on the cold feed as it cat 2? I think.

 

[Millsy 82]

The problem is cheap taps can't cope with the pressure difference so as someone else has said if you do change the taps you need one that mixes outside of the spout.

Otherwise re pipe your cold feed and remove the non return valve.

 

[ShaunCorbs]

Wouldn’t say that tap was good for low pressure installs / unbalanced

 

[Deleted member 84317]

Well depends if the taps at fault can you remove the hot side cartridge

Would reducing the cold pressure by using the isolater valve be worth a go/experiment?

 

[Millsy 82]

Would reducing the cold pressure by using the isolater valve be worth a go/experiment?

From my experience no. You either re pipe or change the tap. You can try fitting pressure reducing valves, using an isolator that will eventually start leaking as they don't seem to like being left inbetween, you can try a low pressure non return valve but eventually you will end up replacing the tap or re piping it.

 

[ShaunCorbs]

Bes sell a banalncing valve for mains to gravity hot water

Water Pressure Equalising Valve - 16711 | BES.co.uk

 

[Welder]

Bes sell a banalncing valve for mains to gravity hot water

Water Pressure Equalising Valve - 16711 | BES.co.uk

That will not work for this Shaun. The max difference in pressure is too large.

That tap is actually not too bad for pressure. However, the only way to make it safe and not have the cold pressurising the hot supply is to swap the tap for two seperate, traditionally valved, taps.
NO modern (1/4 turn) type bath tap will work with pressure this low.
Some kitchen taps keep the water seperated until the spout end (so you'd not get the back pressure) but the hot flow rate with still be appalling.

Sorry. It's bite the bullet time.