Putting sealant into a boiler

[Revan72]

I have a Greenstar 24i junior boiler which has been losing pressure for the past 8 or 9 months now it’s worse when heating is on, if I recharge the pressure up to around 1.5bar it will be down to 0 and in the red overnight, I just bought some Fernox F4 express to try and see if that works but the instructions are not very clear is there any way you can put the stuff into the boiler itself rather than into a radiator, I am not the best at diy by the way! Thanks

 

[Mottie]

That sounds like a big leak. Get it fixed properly, you’ll **** it right up with sealant.

 

[muggles]

Could just need the expansion vessel & PRV looking at. When was it last serviced?

 

[Revan72]

The boiler is 5 years old and been serviced every year since apart from this year I skipped because of the lockdown. So was last serviced July 2019. When the pressure is on 0 the heating and hot water still function ok and I can’t find leaks anywhere in the radiators or the boiler when taking the cover off.

 

[muggles]

Don't take the cover off, it's there to form the safety room seal and should only be removed and refitted by a Gas Safe Registered engineer who can carry out the Regulation 26.9 checks for safe operation. Someone else with your boiler model came on here a couple of weeks ago with their cover off and the boiler firing in a dangerous condition with signs that it was likely to be producing huge amounts of carbon monoxide. They don't appear to have seen everyone's warnings to shut it down and haven't been heard from since...

Have you checked the pressure relief pipe outside to see if it's dripping? Tape a freezer bag over the end and see if it fills up.

 

[terryplumb]

What does the pressure rise to when central heating has been on for an hour ?
If it gets to around 3 bar the PRV will lift and release water out of the system.

 

[Revan72]

Don't take the cover off, it's there to form the safety room seal and should only be removed and refitted by a Gas Safe Registered engineer who can carry out the Regulation 26.9 checks for safe operation. Someone else with your boiler model came on here a couple of weeks ago with their cover off and the boiler firing in a dangerous condition with signs that it was likely to be producing huge amounts of carbon monoxide. They don't appear to have seen everyone's warnings to shut it down and haven't been heard from since...

Have you checked the pressure relief pipe outside to see if it's dripping? Tape a freezer bag over the end and see if it fills up.

I am unable to check outside as I live in a 2nd floor flat so can’t get to the wall outside, I will try and work out how to put this sealer into the radiator and see if that works.

 

[Revan72]

What does the pressure rise to when central heating has been on for an hour ?
If it gets to around 3 bar the PRV will lift and release water out of the system.

When the heating has been on for an hour it goes up to 2 bar, it’s only overnight when all heating is off it will be on 0 again, it only stays up when the heating is on.

 

[ianmcd]

Leak sealer is not the answer

 

[muggles]

From your symptoms I think my first comment still stands - sounds like a PRV & expansion vessel issue. Leak sealer isn't going to fix that, and may well damage your boiler

 

[Revan72]

Leak sealer is not the answer

Ok I read somewhere else it was worth a shot at £20 a can instead of getting a call out people have said it fixed there boilers losing pressure.

 

[ianmcd]

Ok I read somewhere else it was worth a shot at £20 a can instead of getting a call out people have said it fixed there boilers losing pressure.

Nothing to do with the cost of it, it will damage most modern boilers and pumps

 

[Harry Bloomfield]

I am unable to check outside as I live in a 2nd floor flat so can’t get to the wall outside, I will try and work out how to put this sealer into the radiator and see if that works.

That is really not a good idea. You need to find out where the water is escaping from and fix that, rather than the symptom.

No point in wrecking your boiler, for what might have been a two minute proper fix.

 

[kidgreen61]

Listen to the good advice above, your problem is almost certainly exp vessel/PRV, all the crappy sealer in the world won't cure your problem, & may damage the boiler.

 

[Revan72]

Ok thanks for the tips I won’t bother with the sealer, I will probably just leave it for now and keep recharging the pressure, my property is currently up for sale and plan to move in next 6 months so I don’t want to call anyone out and have a potential expensive fix on my hands.