Boiler Pressure Issue

[ForgedPlane]

We have a 15 month old Worcester Greenstar 4000 which was serviced last month. We have recently been experiencing intermittent pressure drops on the system and are having to top the system up to get the boiler to kick in. The pressure drops are not consistent - for example, last weekend we didn't have any drops for 3 days and then it dropped from 1.1 bar to 0.2 bar overnight on the Monday. The installer has been out to check the PRV valve and internal expansion vessel and they don't seem to have any faults. He has said that the most likely reason for pressure dropping now is a leak somewhere in the system, although there is nothing visible, and has suggested adding some Fernox Express Leak Sealer to the system as a next step (either that or calling out a professional leak detection person but clearly far more expensive!) in the hope that this fixes the issue. However, my question is - if there were a leak somewhere in the system, wouldn't the pressure be dropping more consistently? It's boggling my brain that we could not see a pressure drop for days and then suddenly see a huge drop! Any ideas?

 

[oldbuffer]

Possibility: Leak on a radiator with a TRV set low. Only comes on (and leaks) when room temperature below set temperature?

 

[jj4091]

If you can manage without your heating for a few days then isolate the flow and return pipes. If you don't get any drop in pressure then that would suggest a problem with the boiler

 

[Stuckinarut]

Leak sealer on a 15 month old boiler! As above, maybe isolate boiler from system. Check for any old fittings left in if a conversion was carried out, like gate valve bypasses

 

[autobotdad]

Possibility: Leak on a radiator with a TRV set low. Only comes on (and leaks) when room temperature below set temperature?

From the same household .

Thanks for the post.

This is interesting. But would that link into the amount of drop in pressure? As an example, the pressure sat around 1.2 most of today. Boiler has heating up water and heating several times. It dropped a little this evening to 1.0 and then quite quickly from 1.0 to 0.6. This could link in with this theory but I can't see, or feel any leaks around the rads.

My overriding concern is that I'm needing to do this almost daily, so surely water must be dumping out somewhere? How much water is that likely to be for a top up this regular do you think.

 

[autobotdad]

Leak sealer on a 15 month old boiler! As above, maybe isolate boiler from system. Check for any old fittings left in if a conversion was carried out, like gate valve bypasses

From the same household .

Thanks for the post. Is the theory that if you're isolating of the boiler and pressure is dropping, then it's a pressure issue in the boiler itself, whereas if it's dropping when they're open it's likely something on the pipes of rads?

 

[autobotdad]

If you can manage without your heating for a few days then isolate the flow and return pipes. If you don't get any drop in pressure then that would suggest a problem with the boiler

From the same household . Thanks for the post, but not sure I follow. If your isolate the flow and return pipes on boiler and the pressure doesn't drop, wouldn't that mean it's not the boiler?

 

[terryplumb]

Yes that's the theory ,and it doesn't take much water loss for pressure to drop from 1 bar to 0.6
Boiler isolated ,pressure drops indicates boiler is losing water.