Vailiant Boiler Keeps Losing Pressure

tp1988

Jeepers_Creepers said:

Pleased you found the cause.

Yes, 1.8 is a tad high, although not an issue medium term. But best if you bleed a different rad and bring it down to, say, 1.2 bar which is better for your whole system - less likely to blow old rusty rads

I'm a bit concerned at the lack of system cleaning, tho'. The two rads that are leaking have almost certainly corroded through from the inside, which means that there will be sludge in your system.

ahh was hoping that was the issue sorted but again pressure went down to 0.0, so must be another leak somwhere.

Yeah you are right, we have had the previous system for 25 years and never been changed till last week, so bound to be a lot sluge built up.

Hopefully Monday they can get it resolved.

Jeepers_Creepers

Instead of a power-flush, they may instead have added lots of cleaning chemicals beforehand, and left it for a few days before draining and washing through the system?

The irony is, a thorough clean/P-F - by removing the sludge - will sometimes expose small pinholes in the rads that were previously blocked by the sludge, and therefore lead to leaks!

Was your system previously 'vented'? Ie, with a small F&E tank in the loft? That's another potential cause - the increased pressure of a sealed system (~1+ bar as opposed to ~0.2bar) will soon find any weaknesses in your system such as partially-rotted rads. This isn't a 'bad' thing, tho', 'cos these rads were gonna leak at some point anyway!

tp1988

Jeepers_Creepers said:

Instead of a power-flush, they may instead have added lots of cleaning chemicals beforehand, and left it for a few days before draining and washing through the system?

The irony is, a thorough clean/P-F - by removing the sludge - will sometimes expose small pinholes in the rads that were previously blocked by the sludge, and therefore lead to leaks!

Was your system previously 'vented'? Ie, with a small F&E tank in the loft? That's another potential cause - the increased pressure of a sealed system (~1+ bar as opposed to ~0.2bar) will soon find any weaknesses in your system such as partially-rotted rads. This isn't a 'bad' thing, tho', 'cos these rads were gonna leak at some point anyway!

They did drain the radaitors at the start but nothing after that, before this combi boiler it was a vented system, most likley will need to replace all 6 radaitors to stop this from happening in the future.

neilmcl

tp1988 said:

Jeepers_Creepers said:

Instead of a power-flush, they may instead have added lots of cleaning chemicals beforehand, and left it for a few days before draining and washing through the system?

The irony is, a thorough clean/P-F - by removing the sludge - will sometimes expose small pinholes in the rads that were previously blocked by the sludge, and therefore lead to leaks!

Was your system previously 'vented'? Ie, with a small F&E tank in the loft? That's another potential cause - the increased pressure of a sealed system (~1+ bar as opposed to ~0.2bar) will soon find any weaknesses in your system such as partially-rotted rads. This isn't a 'bad' thing, tho', 'cos these rads were gonna leak at some point anyway!

They did drain the radaitors at the start but nothing after that, before this combi boiler it was a vented system, most likley will need to replace all 6 radaitors to stop this from happening in the future.

When I had my old system boiler replaced with a combi 10 years or so ago I was advised at the time that the added pressure would show up any issues with old rads and pipework and that a power flush on an old system isn't always recommended. I was replacing all the old radiators at the time anyway so wasn't such much of an issue.

Jeepers_Creepers

tp1988 said:

They did drain the radaitors at the start but nothing after that, before this combi boiler it was a vented system, most likley will need to replace all 6 radaitors to stop this from happening in the future.

Did they turn up a week or so before and add chemicals to your F&E tank to loosen the sludge, so it could then be drained away I wonder?

Anyhoo, there is no getting away from having to have a clean system with a new boiler, not only for longevity, but for its warranty. If this means your rads crumble in the process, tough

The mag filter will catch much of the sludge passing through (did they suggest to check it every month or so to begin with?), but not all - and I speak from experience. Is your new boiler a 'combi' type? If so, these have particularly narrow waterways (in the P2P exchanger) and are prone to being blocked. You will find on many warranties - and on servicing contracts - that problems caused by sludge are not covered.

What warranty have they offered you? And is it for all parts, and all labour?

Jeepers_Creepers

https://www.installeronline.co.uk/new-british-standard-bs-75932019-installers-need-know/

"For the first time, the fitting of a permanent in-line filter is required in addition to a chemical clean and fresh water flush before inhibitor is added"