Unvented cylinder no cold water to multiple outlets

[Rich55]

Hi, I’m having issues with cold water to multiple outlets. Taps, showers, toilets cold water is fine at the kitchen sink. The hot water system is a Glenhill unvented cylinder. Hot water is fine at all outlets. I assumed the cold outlets not working were from the balanced cold from the combination valve. I replaced the complete combination valve but this didn’t fix the issue.
The neighbour had the very same issue they replaced the combination valve and it cured the issue.
There is a double check valve just after the mains stopcock but the hot water and cold to kitchen are fine so I doubt that is an issue.
Photo below of the new combination valve. I don’t think the issue is the new combination valve as I tried bypassing the valve by linking the feed pipe before the combination valve to the balanced cold pipe. Any one have any ideas?

 

[fowlerboi]

Just want to double check you have the valve the right way round. That top pipe goes to the cylinder feed right?

If the answer is yes then it's not the valve. The valve is fairly simple, if water is going to your hot water cylinder then it will be going to the balanced cold. The issue will be further down the line on the balanced cold, whether that's a blockage or another faulty valve you will have to trace. Realistically I would say changing that combination valve should be done by someone who holds an unvented ticket as it ensures the safe working of your cylinder.

 

[ShaunCorbs]

Sorry to say you need to be g3 / unvented registered to work on unvented cylinders

 

[Rich55]

Just want to double check you have the valve the right way round. That top pipe goes to the cylinder feed right?

If the answer is yes then it's not the valve. The valve is fairly simple, if water is going to your hot water cylinder then it will be going to the balanced cold. The issue will be further down the line on the balanced cold, whether that's a blockage or another faulty valve you will have to trace. Realistically I would say changing that combination valve should be done by someone who holds an unvented ticket as it ensures the safe working of your cylinder.

(For the record i am a qualified plumber and hold an unvented ticket.)
Thanks for the reply, yes the top pipe goes to the cylinder feed. very odd how the neighbour had the very same issue which was fixed by replacing the combination valve.

 

[Rich55]

Sorry to say you need to be g3 / unvented registered to work on unvented cylinders

No need to be sorry, I’m a fully quailed plumber with the appropriate unvented ticket. I didn’t install the system and the pipework is all hidden away so was looking for ideas for help!

 

[ShaunCorbs]

I’m guessing hot water is fine ?

 

[Rich55]

I’m guessing hot water is fine ?

Yep hot water is fine.

 

[ShaunCorbs]

You tried linking cold to the balanced I suspected you have a nrv or another valve somewhere

 

[Rich55]

I did try linking the cold to the balanced which didn’t help. You could well be right, the pipework is installed behind the cylinder in the airing cupboard so really difficult to get to. Tracing the balanced cold it goes down under the floor there’s no other visible valves.

 

[Chuck]

What's the history? Did the problem happen suddenly, gradually, after the house had been sold/empty, etc. Has there been any DIY or other building work done? Do you get no flow, or just reduced flow at the outlets the don't 'work'?

You've ruled out a leak between the combination valve and the affected outlets, e.g. by checking the water meter is not running continuously?

My guess is that you are looking for a valve that someone closed and has not been reopened properly; may appear to be open but has a seized gate or jumper. If the system has been converted from a traditional CW tank in the roof check there isn't an old gate valve still up there.

Maybe a section of pipe has been crushed flat by DIY. Has plastic pipe been used anywhere? Could it be twisted or bent too tightly somewhere?

 

[Rich55]

What's the history? Did the problem happen suddenly, gradually, after the house had been sold/empty, etc. Has there been any DIY or other building work done? Do you get no flow, or just reduced flow at the outlets the don't 'work'?

You've ruled out a leak between the combination valve and the affected outlets by checking the water meter is not running continuously?

My guess is that you are looking for a valve that someone closed and has not been reopened properly; may appear to be open but has a seized gate or jumper. If the system has been converted from a traditional CW tank in the roof check there isn't an old gate valve still up there.

Maybe a section of pipe has been crushed flat by DIY. Has plastic pipe been used anywhere? Could it be twisted or bent too tightly somewhere?

Hi chunk really appreciate the reply. Even if to make sure I’m not being a idiot and missing something simple.
The house is a new build only a few years old. So the system hasn’t been converted. No building work has been carried out since the house was built. My understanding is that it happened quite suddenly.
The house hasn’t been left unoccupied.
There is no water from the cold outlets at all other then a tiny trickle into the toilets through a Torbeck valve. As it’s an equilibrium valve the torbeck valve now doesn’t shut off it trickels in very slowly until it overflows. I guess I need to isolate the toilet to see if I then get a small trickle out of the taps. I didn’t do this yet as it was difficult to get to with no isolation valve.
I haven’t checked the meter. But I can’t hear any water running or see where that much water could go.
The cylinder is on the first floor, the balanced cold pipe goes under the floor in 22mm plastic and is bent rather then elbowed down. Possible kink but been fine for a number of years 22mm plastic unlikely to link for no reason.
I wasn’t going to mention this as i thought it might just confuse the issue but the installer has also teed off the feed to the unvented cylinder after the combination valve and before the cylinder feed. This goes into the wall. And I assume upstairs as the upstairs en-suite all works fine shower, toilet and basin.
It seems the balanced cold straight off the combination valve which goes under the floor is causing the issue.

 

[fowlerboi]

A large amount of debris in the balanced cold pipes made its way into the filters? While unlikely its an easy check and would explain why the float valve may overflow

 

[Rich55]

I will certainly check for debris. If it isn’t that then I did have another thought which is probably even less likely lol

At one point I had the balanced cold outlet on the combination valve blanked off. And I left the balanced cold pipe which was connected to the valve open.

I then slowly turned the water back on. water started coming out of the pipe.. the water shouldn’t be flowing in that direction (back into the combination valve, if it was connected) Could this be cross flow from the bar mixer shower. There are no mixer taps. Unlikely but maybe the bar mixer shower could be part of the problem. There was quite a lot of debris solder ect in the original combination valve I replaced.

 

[ShaunCorbs]

Yes bar mixer but depending on age they might not have check valves in hence why water was flowing back

 

[Rich55]

Yes bar mixer but depending on age they might not have check valves in hence why water was flowing back

The house is a new build so can only be a few years. Probably no check valves like you say.

 

[ShaunCorbs]

The house is a new build so can only be a few years. Probably no check valves like you say.

Do they have a bath tmv3 under it

 

[Rich55]

Do they have a bath tmv3 under it

They do have a bath, I haven’t checked behind the panel for a tmv3 tho

 

[ShaunCorbs]

First port of call I would

 

[Rich55]

First port of call I would

are you saying they could have come off the tmv and instead of just going to the bath they may have taken that feed to the whole main bathroom then down to the cloakroom below?