Cylinder coil split?

[Dan Robinson]

 

[Boodle]

Ok. So overnight the mains water was turned off, and the ballcock on the cylinder header tank was already tied up. The level in the f&e tank stayed the same, and the cylinder header tank rose around 1cm, but the hot water cylinder did come on this morning so I guess warm water will expand slightly.

Will there be a nrv in my shower mixer that can be replaced? Should I put another nrv as close to the shower as possible, after the pump this time? How likely is it that I fitted a diff nrv in the first place and how dirty do they get?

 

[denso13]

I would try and isolate the shower first, just to confirm that is where the problem lies. If you put in another NRV and it still happens you will be back to square one.

 

[Boodle]

Ok, that's Saturdays job then. Without taking up the bathroom floor I can only isolate the hot feed before it branches to the shower and bath. This will at least rule out the bathroom and kitchen sink mixers.

 

[Agile]

It is always a risk to have a system with unbalanced supply pressures and mains pressure on the cold taps.

Is seems pretty common for joystick type taps and many showers to leak internally from cold to hot ( when turned off ).

They should always be fitted with NRVs. But rarely are! They can be fitted anywhere along the supply pipe to an outlet. They do not need to be close to the oulet.

I would not greatly trust single NRVs to be very reliable and if the mains pressure was at all high would always fit double NRVs.


A few months ago I reluctantly went to a lady who had a British Gas contract and an unvented cylinder. They had made many visits to cure intermittent discharges from the pressure release valve on the unvented cylinder but seemed unable to diagnose the problem.

I traced the problem to a leaking joystick tap on a basin in her en-suite.

Due to the controls on the unvented cylinder it would only discharge when the mains supply pressure exceeded the set pressure on the unvented. That was mostly overnight when mains pressures can rise significantly.

Tony

 

[Boodle]

It is always a risk to have a system with unbalanced supply pressures and mains pressure on the cold taps.

Is seems pretty common for joystick type taps and many showers to leak internally from cold to hot ( when turned off ).

They should always be fitted with NRVs. But rarely are!

I would not greatly trust single NRVs to be very reliable and if the mains pressure was at all high would always fit double NRVs.


A few months ago I reluctantly went to a lady who had a British Gas contract and an unvented cylinder. They had made many visits to cure intermittent discharges from the pressure release valve on the unvented cylinder but seemed unable to diagnose the problem.

I traced the problem to a leaking joystick tap on a basin in her en-suite.

Due to the controls on the unvented cylinder it would only discharge when the mains supply pressure exceeded the set pressure on the unvented. That was mostly overnight when mains pressures can rise significantly.

Tony

Thanks for the advice, this is the first house I have worked on that has a hot water cylinder, all the others have run from a combination boiler, and I never had any issues.

Is there a maximum pressure a single nrv can resist?

 

[Agile]

In theory, from the construction they should easily resist 3 bar. The higher the reverse pressure the greater the pressure closing the seal!

But they sometimes get dirt stuck under the seals.

Loft tanks are not the cleanest way to handle water. Even if they do have the correct lid they can have lime scale deposits inside.

But be aware that in your own case you and those advising here are only trying to guess at what is happening to your system.

A NRV should not leak when everything is new and clean. But a double NRV greatly lessens any chance of leakage.

Tony

 

[denso13]

But be aware that in your own case you and those advising here are only trying to guess

You are doing it again! Do you not see how patronising your posts can be?

Are you not "guessing" every time you post what you think is a solution?

OP, ignore Agile's advice. NRV's should not always be fitted to mixer taps - it depends on the system and tap design.

 

[Agile]

But be aware that in your own case you and those advising here are only trying to guess at what is happening to your system.

Tony

Denso, please do try to read what I have actually said!

"those advising here" includes me equally with everyone else!


Because I have been to so many mixer taps/showers with leaking seals, I would always advise fitting an NRV when the supply pressures are unbalanced.

I would expect that most tap suppliers would also advise them. But unbalanced supplies are ( luckily ) pretty rare now that combi boilers and unvented cylinders are the usual type of system.

Boodle, do you really want to ignore my advice?

 

[ianmcd]

Boodle, do you really want to ignore my advice?

Boodle you would be better listening to a plumber, who Agile thinks he is far superior too.

 

[bernardgreen]

But unbalanced supplies are ( luckily ) pretty rare now that combi boilers

What about pressure drop ( which is flow rate dependent ) through the combi heat exchanger without a matching reduction on the cold supply ?

 

[Boodle]

Well, that got confusing.

I'll isolate the bath and shower, and see what happens.

 

[FiremanT]

Boodle,your thread got caught up in the current round of(according to the Mods) Agile baiting.It is because he writes a lot of drivel and often incorrect content. But try not to get sidetracked by it all. All comments here are calculated guesswork, based on experience, and the more RELEVANT info is supplied, the better the chances are that the solution will be discovered.

And, BTW, there must be hundreds of thousands of "unbalanced" H&C systems still around, so not exactly "rare" (Another Agile blooper)

 

[denso13]

Well, that got confusing.

I'll isolate the bath and shower, and see what happens.

Apologies Boodle. Let us know how you get on.

 

[Boodle]

I appreciate everyone's input so far. It's given me plenty to think about and check.

Finger crossed I can sort it easily, the how water tank doesn't stay warm long!