Losing pressure, but no leak detected by gas tracer

[Sarah321]

I think it is unvented, yes - they have given me a quote to to the following work 're-pipe airing cupboard to include and auto air vent and to replace teh 2 port valve for a spring return type'. They had a devil of a job refilling the system with water after it had be drained due to the fact that it's unvented.

As for pressure testing the system - they have gone up to 2.5 - 3 bar testing with water, but I was told that they only went to 1 bar when pressure testing with gas.

I have taken some photos of the airing cupboard upstairs with the 3 tanks if that's any use! Thank you all so much for taking time to talk about this - I am really grateful.

 

[Sarah321]

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• Sarah321
• 7 Feb 2012
• 1

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• Sarah321
• 7 Feb 2012
• 1

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• Sarah321
• 7 Feb 2012
• 1

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[Onetap]

Yes and no Onetap

They only pressure tested to 1 bar so no it wouldn't.

The bigger worry is if it's an unvented cylinder, then that will not be the problem, as the pressure within the cylinder would also increase the system pressure, (in reverse if you know what I mean)

It would be pointless to pressure test the system unless the unvented cylinder had been drained.

If it is an unvented cylinder, is would more probably leak into the heating system, causing a pressure increase, if the coil was leaking (I think that's what you said). IMHO it is more likely to be the boiler heat exchanger, with the water going into the condensate drain.

Maybe the way to establish what is happening is to isolate the heating system, cutting in valves if required. Then run the boiler to heat the cylinder only, with the hot water being run down the drain at a rate equal to the boiler output. If the return is kept above 60 degC, there should be no condensate and a pressure loss & water from the condensate drain shows the heat exchanger or its seals are knackered. Otherwise tip some dye into a towel rail and just run the cylinder, as above. The dye will show up in the DHW or the condensate drain if there is still a leak.

 

[Onetap]

I think it is unvented, yes - they have given me a quote to to the following work 're-pipe airing cupboard to include and auto air vent and to replace teh 2 port valve for a spring return type'. They had a devil of a job refilling the system with water after it had be drained due to the fact that it's unvented.

That's a bit of a mess, but it's not relevant to the problem with the leak; don't let them touch it until the leak is resolved. There should have been a 2-port valve (usually a Honeywell) supplied and fitted with the cylinder and virtually all domestic 2-port valves are spring return.

PS And isolate and disconnect the filling loop whilst it is being tested, to ensure there are is no leak back into the mains supply.

 

[doitall]

I agree don't let them do any work outside of the leak.

They'll try to recover the money their incompetence is costing

 

[gas112]

OP .
Way back you say hey isolated the boiler and you had a bowl under condensate to catch anything coming out .
And you said the pressure still dropped.
Have i read it wrong, did it drop when isolated or the minute they turned it back on.

 

[Sarah321]

OP .
Way back you say hey isolated the boiler and you had a bowl under condensate to catch anything coming out .
And you said the pressure still dropped.
Have i read it wrong, did it drop when isolated or the minute they turned it back on.

While the boiler was off, the pressure went down to zero (very quickly), but nothing came out into the bowl.

 

[gas112]

Providing boiler was properly isolated then the leak has to be on the boiler somewhere , i cannot believe they would then investigate anything else on the system.
After such a result i would be isolating the boiler emptying the system and disconnecting boiler tails to make sure valves where not passing. If they are not passing there is no point looking elswhere
All very basic to be honest

 

[compheat]

A good friend of mine, who is also a very good plumber had a similar fault on a band B condensing comi. He'd done every thing possible to trace the leak but couldn't find anything

Thats when I turned up anyway the leak was traced to a fault on the recouperator that was leaking internally and running down the condense pipe.

If youve spent so much money trying to find this leak and you know that its the boiler why not just change that???

 

[Agile]

Any loss of pressure is a very simple problem, basically just a leak!

I really cannot understand how so many people can act so incompetently!

I wonder if anyone has actually checked that the PRV vent pipe really is continuous through the wall?

Tony

 

[middlesbrough]

Agile

I was thinking that myself , ive seen enought wc o'flows just into the cavity.

Im assuming all D2 pipes were checked both from the cylinder and boiler should they be one there.

 

[wehr]

Hi, did your problem ever get sorted? We've had exactly the same trouble over the past two weeks. Steve