Water tank overflowing outside house

[Milloy]

Hi - have had a problem now with the cold water tank that feeds the hot water cylinder over flowing outside our house.

This first happened on boxing day and strangely happened overnight when no heating or hot water was switched on.

As the cold water tank was old - (and it later became apparent the over flow blocked) this emptied over my dining room.

So - believing that it was a hole in the old cold water tank, we had this replaced.

About a week later again overnight and again with no hot water or heating switched on (gas fired boiler system) same thing happened. This time plumber came out and believed it was a faulty thermostat on the hot water cylinder boiler so changed it and put a new overflow pipe outside the house - at least now stopping more water coming into my dining room.

All well for 3 weeks - then last week trickles of water from the over flow outside the house - again over night and again no hot water or heating switched on.

On investigation the pipe that takes the cold water from the cold water tank to the hot water cylinder was warm - at the cold water tank in the loft. More so the water in the cold water tank was warm.

Drained system and problem stopped. A week passes by then happens again.

Called plumber and he now seems to think it is to do with the cold water pressure pushing back through the system.

The hot water pressure is so low in our house there is a pump to push the water through when the hot taps are turned to draw.

He believes that the problem could be happening at a mixer tap and somewhere the cold water pressure is pushing the water back through the whole system.

Whilst I trust his judgement - I was wondering if anyone else has any views on what the problem could be?

He is coming to fit a pressure reducing valve this week so fingers crossed...

Sorry for long thread, but as you can see we've already changed a lot of things on our system and we're fast running out of cash...

Would really appreciate some views on this..

 

[crockett]

question - is the feed and expansion tank in your loft higher than the larger cistern ? If so, it could be a failure of the coil inside your cylinder, which would cause this problem. Worst case scenario, new cylinder Without viewing though, it could be a couple of things, the advice your plumber gave you being one of them.

 

[dextrous]

He is coming to fit a pressure reducing valve this week so fingers crossed

Think his reasoning is sound, but not sure about a PRV Think double check valves on the hot water supplies to the mixer taps would be more appropriate.

 

[crockett]

Dextrous makes a valid point there. A check valve would be a better option.

 

[Milloy]

Thanks Guys - for my info what's the difference between a check valve and PRV?

 

[tamz]

A pressure reducing valve does what it says, reduces the incoming pressure.

A check (or double check) valve stops backflow.

Check valves are the solution.

 

[TicklyT]

A check valve on the hot feed to a problem mixer tap / shower valve should cure the problem, if that is the problem. They should be fitted anyway.

Try closing the service valves on mixer taps / shower valves overnight to see if that cures the trouble

 

[ManxPlumber]

When you had a new CWST fitted, did you replace the float valve and was the water level set?

...water from the overflow usually points to a knackered diaphragm washer

 

[Milloy]

Ok. The plumber came out and instead of fitting valves to each tap area, he fitted one way to the pipe feeding the hot water cylinder.

One on the cold water feed to the cylinder from the cold water tank, and one to the hot water feed from the cylinder to the taps.
All well - then yesterday same problem with water coming from the safety vent into the cold water tank.

Called another local plumber who said due to having 3 to 4 bar pressure in the area he didn't think no amount of valves was going to solve this problem and what I needed was a pressurised cylinder. Quoting £3k to £3.5k to fit one.

Question I have is as follows:
Are the points made above about putting valves around all the taps, showers still valid (and a cheaper option than a pressurised cylinder)?

And - as in the future I will want the cylinder removing, to aid a loft conversion, can I replace the whole system with a combi boiler system and will this work ok?

Please help - losing my mind, and if I have to spend £3k I'd rather spend it relacing the whole system with a combi boiler...

 

[Nige F]

Ok. The plumber came out and instead of fitting valves to each tap area, he fitted one way to the pipe feeding the hot water cylinder.

One on the cold water feed to the cylinder from the cold water tank, and one to the hot water feed from the cylinder to the taps.


Please help - losing my mind, ...

I`m losing the will to live if that`s what "" Plumbers " in london get up to

 

[Milloy]

So I gather you think that was a complete waste of time then?

Ok - if you can solve my problem - let me know, I'll pay!

4 bar pressure apparently in this area so if it is putting check valves on taps that will solve it - please say and I'll happily pay for this and tear my bathroom to pieces to fit one to the shower.
As you can hopefully understand I am reluctant to do this until I am convinced that this is the answer.

Thans