Small central heating leak?

[drives]

Hi all,

We have a large-ish central heating system with 16 radiators. System boiler. We have recently swapped out the old vented cylinder and gravity fed CH system for an unvented cylinder and sealed CH system. Our issue that I need to sort is that the pressure gauge is consistently dropping around 0.05 bar a day.

As a bit of background, when we had it gravity fed I was regularly bleeding the upstairs radiator directly above the boiler- on a weekly basis. The water was always quite black so I thought it might possibly be some corrosion contributing to the issue, but we have had one or two plumbers round over the last couple of years to service and they suggested a small leak somewhere. We definitely have no visible leaks so if we do, I can only surmise that it is ground floor level under the floorboards.

For unvented we now have a magnetic filter and largely due to the above observations I requested a power flush. When bleeding the rads all comes out clear now. I have checked and rechecked all radiator connections. No patches on ceiling or floors. No obvious damp.

What would people generally recommend as next steps? Plumber/specialist leak detection company? A leak stop solution to add to the CH system? We are currently renovating the house albeit annoyingly I have already redone around a third of the downstairs flooring- but, I guess it could still be effectively surveyed at least from other rooms by taking out a floorboard or two.

Anything else obvious I can check? Boiler seems fine and is regularly serviced.

 

[foxhole]

New hot water cylinder..?

 

[terryplumb]

I assume you are losing 0.5 bar ,not 0.05 bar. If so, water is definitely being lost from the system.
Have you checked the PRV pipework for any signs of water dripping externally ?
How old is the boiler ?

 

[drives]

I assume you are losing 0.5 bar ,not 0.05 bar. If so, water is definitely being lost from the system.
Have you checked the PRV pipework for any signs of water dripping externally ?
How old is the boiler ?

So I am losing 0.05 bar a day. Essentially lost around 0.2 bar over the course of around 4 or 5 days- this is how I have measured it.

Is the PRV pipework the white plastic pipe that runs from the bottom of our boiler? It runs internally to the washing machine drain (utility room). I can't see any obvious signs but will monitor that more closely if that's the right pipe. I know the plumber installed some kind of additional pressure relief valve in the loft with the new hot water cylinder. I have checked all of that pipework and it is all dry.

 

[terryplumb]

The white pipe is the condensate drain ,and water will trickle from / through it when the boiler is burning gas.
The pressure relief valve in the loft is more likely linked to the unvented cylinder.
Show us some pics of pipework below the boiler or tell us the make and model.
How old is the boiler....???

 

[drives]

Valiant Ecotec plus 428- around 15 years old I believe.

Here's some photos. I've included some of the cylinder and what I assume is the pressure relief valve by the side of the pressure gauge.

 

[terryplumb]

You are correct ,the PRV is to the left of the pressure gauge. The copper pipe below the tundish should go out externally ,and be visible outside. If there are no signs of water dripping at the tundish then the PRV can be ruled out.
That leaves a leak on the system ,or a pin hole leak in the heat exchanger of the 15 year old boiler.

 

[drives]

You are correct ,the PRV is to the left of the pressure gauge. The copper pipe below the tundish should go out externally ,and be visible outside. If there are no signs of water dripping at the tundish then the PRV can be ruled out.
That leaves a leak on the system ,or a pin hole leak in the heat exchanger of the 15 year old boiler.

Yes the pipe goes out externally. The turndish is bone dry.

I am guessing if there was a leak in the heat exchanger it would be visible underneath? No signs of any leaks there...we do have it serviced annually as well so would hope that they would have found an issue.

Thanks very much for your help. Assisted in understanding my system a bit better and ruling out some possibilities. Guessing it might be into the realms of specialist leak detection, or looking at an additive to the CH system albeit latter feels like a bit of a bodge or destined to fail a bit further down the line even if it does fix it?

 

[terryplumb]

If the heat exchanger is pin holed ,water will trickle out the white pipe when the boiler is NOT operating. It will not be leaking under the boiler ,and may not be obviously apparent if the white pipe is sealed into waste pipework.
Adding leak sealing chemicals is not something I would advise ,and specialist leak detection company's are expensive and often not successful.

 

[drives]

If the heat exchanger is pin holed ,water will trickle out the white pipe when the boiler is NOT operating. It will not be leaking under the boiler ,and may not be obviously apparent if the white pipe is sealed into waste pipework.
Adding leak sealing chemicals is not something I would advise ,and specialist leak detection company's are expensive and often not successful.

Right ok. What would be your recommendation? We have pipework under ground floor floorboards- this is my main concern.

Will double check the pipe. It just runs into a wider waste pipe. Bit awkward but not sealed and can check

 

[terryplumb]

Firstly rule out the heatex. It there is a crawl space below the ground floorboards ,lift a few boards and get down to take a look.