CH system leak but where?

[Blacky]

Hi

I have a pressurised system for both CH and Hot water with a tank. The boiler is a Worcester Bosch Greenstar.

A few years ago I thought I had a leak in pipes buried in the concrete floor, so had new pipes fitted dropped from the first floor. All good and system working again.

Now a few years later the pressure is dropping again. Refill to 2 bar and within 5 hours it is back to zero, as measured by the pressure gauge on the boiler in the loft, and without the boiler being on ie it is all cold.

There are no drips from the pressure relief pipe outside. None of the radiators or pipes are leaking other wise there would be stains on the ground floor ceilings.

If I switch the system on hot water flows round the system but within a few hours at least 3 of the radiators are completely empty of water.

Can anyone who understands how these systems work give me a clue as to where to check next please.

I'm thinking that I might put a pressure gauge on the CH side and isolate the boiler. This would identify if it's the boiler that's at fault.

Anything else I should be trying?

 

[WLF85]

Are you sure the radiators are "completely out of water"?

Any reason why you are pressurising a cold system to 2 bar?

 

[Blacky]

When the system is on and the radiators are warm I can feel warm water at the bottom of the empty radiators but the radiators go cold about 2 inches from the bottom and all the way to the top. When I bleed the radiators I can feel the warm water moving up the rad.

No reason for 2 bar other than its still in the green zone.

 

[WLF85]

How can there be warm water in the bottom of an "empty" radiator? If there is water in there it's not empty is it?!

Your description is all over the place.

Hopefully someone else will understand your magic radiators and offer some guidance.

 

[ollski]

if its a greenstar cdi its usually a cracked primary heat exchanger discharging through the condensate pipe. Are you getting water running down the condensate pipe with the boiler turned off?

 

[Blacky]

Hi WJF - ok, maybe the radiator isn't completely empty but it's 90% empty. Does that make any difference? I thought that the siginifcance was that most of the water has drained away rather than work out what % had drained away.

Hi ollski - yes it's a Greenstar 30cdi Classic.. The condensate pipe discharges into the soil stack so it's not visible. All inside the loft space. I will find a joint and see what's happening. Thanks for the input.

 

[WLF85]

Hi WJF - ok, maybe the radiator isn't completely empty but it's 90% empty. Does that make any difference? I thought that the siginifcance was that most of the water has drained away rather than work out what % had drained away.

Hi ollski - yes it's a Greenstar 30cdi Classic.. The condensate pipe discharges into the soil stack so it's not visible. All inside the loft space. I will find a joint and see what's happening. Thanks for the input.

I never said you should work out what percent had "drained away". You're the one who said the radiators were "completely empty".

 

[Madrab]

To identify whether boiler or not ... Pressurise system, shut off boiler flow and return valves. If pressure still drops then it's the boiler. If it doesn't but drops when you open the valves back up, it's in the CH circuit ... simples.

 

[Blacky]

Thanks madrab. Did what you suggested & it's not the boiler.

Yesterday I was in the house & topping up the heating every couple of hours as the pressure was dropping from 2 bar to zero that quickly. Then I noticed that the cold water tank in the loft was over flowing. On checking this tank it's full of dirty water, which feeding through into the hot taps in the bathroom.

I bet the leak is in the hot water tank. I checked the pipe which runs from the cold water tank into the hot water tank and it was warm. So water must be flowing from a hole in the coil inside the hot water tank, into the hot water and then back up into the cold water tank.

Hot water tank now scheduled for replacement, and hoping that the mystery is solved.

Thanks for your input. Much appreciated