Confusing overflow issue I've had for over 6 months

Thank you for taking a look...

Like I said I've had this issue for over 6 months now and have multiple different plumbers look and the problem and still no one knows what seems to be the issue.

Firstly...

I live in a 3 floor block of flats on the top floor, and have a new combi boiler installed 4 years ago.

This problem started at around the beginning of summer this year, when I noticed the cold water tap was sometimes running warm water, I gave it a quick google and was informed that it could be the heating of the pipes during the summer, since this was an intermittent issue, I didn't think much of it. Around the same time we started getting water overflowing, at this time we wasn't aware if the issue was connected or still is.

The plumbers have checked the water tank and the ball valves and said that's not the issue, we recently changed all our mixer taps in the house, and still last night we still had the water running from the overflow pipe.

The plumber also said the it could be my neighbors with the issue since only our two flats was experiencing this issue and no one else in the block of flats is getting hot water from their cold tap, I'm waiting to hear back when they get their taps changed to see if the problem is fixed.

I should also mention I don't have access to the loft where the tanks are stored, I have to call out someone from the council with a key to the access ladder and key to the loft, and also that the tanks are communal.

The only issue I have mentioned which the plumbers have not looked at is, our boiler; when the the taps and central heating setting is turned on, and radiators are turned of at the thermostat, they will come on regardless if the taps and being used. So we set the boiler to only supply the taps, and we've back-seated this problem when the overflow started, and it just occurred to me whether the two things could be connected.

I know it's a lot of information, but we've it's been 6 months and we're no closer to fixing it. It's become a lot worse in the recent couple of days, where have the taps running constantly to stop the overflow pipe from running.

Thanks for the help in advanced.

 

1. With warm water coming from the cold taps and an overflow running, I'd suspect an overheating hot water cylinder pushing hot water up the vent pipe into the cold water storage cistern.
2. If you have a combi boiler it is unlikely that you have a hot water cylinder, so if 1. is correct, unlikely to be your problem.
3. More likely to be the neighbour experiencing the same problem. Could be a boiler problem or a failed immersion heater thermostat.

 

Thanks for the quick reply.

Yes I don't have water cylinder, however I'm not sure of the plumbing setup my neighbor has but I assume its similar since our block of flats had boilers changed around the same time.

So it could be my boilers thermostat? because like I said the radiators would turn on by simply using the taps in the house, could that result in a different of water pressure, causing an overflow?

 

You have a combi boiler and a cold water cistern? What does the cistern supply, bathroom? Any reason that the cold water cisterns supply to your flat was retained and not moved over to the mains as you now have mains hot water to balance the supplies?

Does your neighbour have a combi too? May be time to move over to full mains and decomm the cold cistern

Your radiators coming on when the hot water is run is another issue and wouldn't normally be connected to your water issues.

 

I assume that's the setup I have no way accessing the loft.

I've had 6 or 7 plumber come take a look, they all mentioned I was connected to the tank, and only suggested that the council should of disconnected me from the tank when the boiler was installed.

I'm still waiting for my neighbor to get his taps changed, how likely is it be that or should I start making calls to the switch over to mains.

Thanks for the help.

 

Sorry don't know how to remedy the warmed cold water pipes but consider the possibility of legionilla growth in the potable cold water supply.

Came across legionilla whilst staying in an apartment abroad.

 

I'm not sure that's the case we've had multiple plumbers in the roof looking at the tanks and they said that its all fine, ball valve is not rusty or anything wrong with the tanks.

However I was told that I should not be connected to the tanks in the loft if I have combi boiler, is this true?

Could that be causing the overflow ?

 

A friend of mine has an ex LA flat - combi boiler does hot water to sink, bath, basin. Cold mains water to sink and feeds combi. But the WC and cold to bath and basin are from a communal roof tank. The question is What overflow is running @ your flat ?

 

Yes I think the overflow is from the communal tank.

 

Do you have a shower mixer in the bathroom ?

 

I do, but I've replaced it yesterday with a brand new one.

 

Ah, I wondered if it might have leaked mains hot from the combi to the tank fed cold.

 

How would I remedy this ?

 

On each supply pipe ( ie, Hot and Cold) fit a single check valve - That is the name of the valve, as opposed to a double check valve which is used (for example ) on an outside tap . Easily obtained from screwfix etc. connects with compression ends complete. Then the water should only go the correct way.

 

The check valves would certainly remove the possibility of backflow through the cold, only thing I would add to that though is when using them on a gravity fed supply even a single check valve could affect the flow quite significantly.

The council boiler swaps were done on the tightest of budgets, moving the whole flat over to mains was an extra cost that they didn't need to spend, they did have to upgrade the heating system though to meet government guidelines and incentives.

Get the cold swapped over to the main, should be reasonably easy to do and then share the costs with your neighbour. Probably could have done it for the same price as swapping out all the taps and it also removes the thought of at least 50 gallons of cold water (nearly a 1/4 ton) resting above your head