Loosing pressure, but no sign of leak

[unclebob1]

Hi all,

I have an intergas her 40 SB boiler, acv smart hot water tank, 7 ufh loops and 4 radiators.

I have three zone valves and a white expansion tank


System was installed 2 and a half years ago.


I'm finding that the boiler is cutting out due to low pressure, I top it up, to 1.2 or 1.3 bar, and a few days later, it's back to low pressure.


Today I topped it up to 1.3 bar. Bathroom sink cold water turned on, and the pressure dropped to 1.1 bar.

Shower turned on (cold and hot water), and pressure dropped to 0.9 bar. Boiler was off throughout and the top up loop was off on both sides.


I have put a bit of tissue in the tundish to see if any drips, and like wise around the Addy filter in and out. All are dry.

I can see no obvious water leaks on ceilings, and no works where ufh pipe may have got damaged. Leak increased after last service (heat exchanger removed and cleaned etc, and intergas replaced the seal on the heat exchanger as it was the wrong colour...


What else can I do to try and find the leak?

 

[dilalio]

Running taps should not affect the pressure of the sealed heating system.

 

[unclebob1]

Running taps should not affect the pressure of the sealed heating system.

I thought the same, only thing I can think of that may cause this is in hot water tank expanding is causing the difference, or expansion vessel?

 

[dilalio]

If you are losing "system" pressure, this is within the sealed circuit and is caused by either a leak or an expansion problem.

The expansion vessel for the unvented cylinder (white one) is separate from the heating expansion vessel, within the boiler.

This needs to be checked for proper air charge and for any defects.

Best to first check the discharge pipe from the boiler to see if the PRV is letting by and water is escaping that way. It's unlikely that this discharge is routed through the tundish for the UV. Trace this from the boiler and check for let by.

 

[unclebob1]

Thanks for your help Dilalio, it looks like my expansion vessel is behind the boiler, so will have to get someone out to have a look at that, meanwhile, the water escape via PRV - i only have one pipe going into the waste for my boiler, i assumed this is the condenser waste. Would it come out of the same pipe?

Also if i set pressure to 1.5 bar and isolate the feed/return, and turn off the boiler, would i still see a drop in pressure if the heating expansion vessel has a fault?

 

[Nozzle]

My money is a leak in your cylinder, from primary to secondary.

Nozzle

 

[unclebob1]

My money is a leak in your cylinder, from primary to secondary.

Nozzle

I hope not - its a 3 year old tank in tank system, and in that case, i would expect the water pressure from the hot water to top up the radiator water when there is no demand? The hot water is at mains pressure, so more then the radiator water.

 

[Gasguru]

Find the boiler pressure relief valve...AFAIR it's connected to the flow pipe on the RHS under the boiler. Check this is not dripping.

 

[unclebob1]

So I have dripping from a copper pipe outside, which I believe is connected to the PRV.

The PRV is inside the boiler so looks like a job for someone to come by, it's a drip, maybe two drips in 20 seconds... Is it a case of opening the valve and let it clear out anything stuck?

 

[oilhead]

Always worth a try, but don't hold your breath.

 

[terryplumb]

So I have dripping from a copper pipe outside, which I believe is connected to the PRV.

The PRV is inside the boiler so looks like a job for someone to come by, it's a drip, maybe two drips in 20 seconds... Is it a case of opening the valve and let it clear out anything stuck?

Possibly ,but more likely a new PRV will need to be fitted.

 

[unclebob1]

Ok, either way it's inside so will need to get someone out

 

[unclebob1]

Does warranty cover this part? If so do I get in touch with intergas or normal installer?

 

[terryplumb]

That depends on the warranty ,who gave it to you and exactly what is being warranted. You must have that information surely.

 

[Gasguru]

No it's almost certainly down to lack of proper servicing ie. ensuring the red expansion vessel is properly re-charge. However, with such a large system...the underfloor pipe work and the significant primary water within the cylinder it's quite likely the 8 litre expansion vessel behind the boiler is insufficient. So either a larger single vessel or an additional vessel should have been utilised at installation.
Ideally for a typical 2 or 3 storey property the cold pressure would be set around 1 bar and you wouldn't want to see the pressure rise to more than 2 bar with the heating and hot water on and up to temperature.