Pressure Relief Valve

Joined
19 Sep 2007
Messages
114
Reaction score
0
Location
Oxfordshire
Country
United Kingdom
Hi,

I've got water dripping through the tundish on my megaflo system. Quite a stream of water is coming out of the overflow pipe.

I've recharged the air gap and still have the issue. The water is cold so is not coming from the pressure relief valve on the cylinder. It continues to drip even if I isolate the water supply, so it appears to be coming from the water inlet pipe at the bottom of the cylinder.

I think I've narrowed it down to the pressure relief valve on the incoming supply...

https://www.unventedcomponentseurop...unit-pressure-relief-manifold-core216000.html

The question is should I get the whole thing replaced or just the cartridge...

https://www.unventedcomponentseurop...2116-pressure-relief-cartridge-zrc214009.html

Is there anything in the whole unit that could have failed or will replacing the cartridge solve the problem in most cases? This whole valve was replaced 3 years ago.

Don't worry, a local plumber certified to do this work will change the kit for me. I won't be taking any chances!
 
Sponsored Links
Hi,

Just a thought...

The boiler was serviced recently and the dripping was noticed a few days later. Is this a coincidence or could it be connected?
 
I would try charging the bubble up again, try doing it a few times, these units don't always replace the air bubble properly using just the T&P. I tend to drain them further down than just using the T&P till it stops, open a hot tap and release the pressure from the cylinder, keep the hot tap open and then drain the cylinder more and then re-fill
 
Thanks for that. Can you explain further how to do this.

I normally isolate the water, turn on the lowest hot tap, hold open the pressure relief valve on the side of the cylinder and close it when water stops running from the tap. Then let water flow back in again and turn off the hot tap.

Am I missing a step?
 
Sponsored Links
Nope, not missing a step and that's the megaflo usual steps but I always drain more water out using the drain off valve, the more air you introduce the more likely the bubble will be created properly.

I have had it on occasion where it hasn't reset the bubble properly using just the T&P valve.
 
Hi,

Just tried but no success I'm afraid.

I can hear water going through pipes in the airing cupboard even when the water supply is isolated both in the airing cupboard and via the main stopcock.

Any other thoughts?
 
I'm guessing the bubble has been low for sometime and the PRV has been dripping for a while and may just have debris on the seating.
You could wrap a dishcloth around the tundish (to stop the water splashing everywhere) and open the PRV to flush the seating through.
Flush it several times until it appears to close properly.
However, even a drop every minute will soon add up and cost you on the water meter.
 
OK, just tried that but again no luck.

You're right about the water, I dread to think how much we've lost over the last few days!
 
So when you isolate the system via the mains stop tap and the feed to the hot water cylinder, do the taps still run, even just a trickle?
 
Simple thing to do is undo the nut from tpr valve or expansion relief valve and see what one leaks then replace it!

could obviously be a dodgy pressure reducing valve but doubt it.
 
Simple thing to do is undo the nut from tpr valve or expansion relief valve and see what one leaks then replace it!

could obviously be a dodgy pressure reducing valve but doubt it.

whatever one it is dripping try opening it so it snaps back a few times. It helps sometimes but rear
 
Madrab

OK, I turned the mains stopcock off and also isolated the feed to the cylinder.

The hot tap continues to run normally, the cold tap is producing NO water at all.

Gasplumber

The TPR valve (I assume you mean the valve on the side of the cylinder) is definitely not leaking as the water going into the tundish is cold. I tested this earlier by letting a small amount of water through and it remained warm after travelling to the tundish.

I've tried snapping the valve loads of times on both valves, but no change.

I'll try and post a few pictures.

One thing to mention is that when all water is isolated, water is still going to the tundish and you can hear water 'noises' in the airing cupboard.

Any more ideas?
 
If you leave the hot water tap open does it stop eventually or does it just keep running even with the stop tap supplying the cylinder shut off? If it doesn't ever stop then that's why you can't replenish the bubble and why the cold water expansion is still passing through the tundish.
 
The compressed bubble acts like a large energy reservoir...after isolating the cylinder you need to leave the hot tap running for a while until the bubble pressure energy dissipates at which point the water should stop.

Does the main stopcock isolate ALL the cold taps?

A rare situation can occur whereby some cold taps (especially the kitchen sink) are fed directly from the mains rather than from a take off after the pressure reducing valve. If the street pressure is particularly high this can mean that the cold tap pressure can be somewhat higher than the hot tap pressure and there exists the chance of backflow across a faulty mixer valve ie. the hot side becomes presurised above the pressure reducing valve setpoint.
 
Madrab

I'm pretty sure the hot water will stop but I didn't want to leave it going at the moment just because so much water is being wasted. The water pressure has been fine and continues to be so, if that is relevant.

Gasguru

The main stopcock does stop ALL the cold taps.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top