Do I need an additional expansion vessel

[Trevor C]

Before I call a plumber .........

My boiler (Gloworm 18sxi) slowly loses pressure and I'm having to regularly top it up. There are no obvious leaks anywhere and no discharge from the PRV as far as I can tell.

Just reading through the manual for the boiler, it says that it has an internal 8 lire expansion vessel and a maximum system content of 130 litres and there is a note saying "For larger systems use an additional expansion vessel". It provides a schematic on where to place the additional vessel.

I have a 4 bedroom house with 15 radiators, five of which are doubles. I've read that a rule of thumb is 10 litres per single radiator, so that would make my system something closer to 200 litres.

1. Do I need to get a plumber in to add an additional expansion vessel?
2. Is this likely to have anything to do with the loss of pressure issue?

Thanks

 

[ShaunCorbs]

Normally 1l of expansion per rad so a 15l one is needed but that wouldn't cause your loss of pressure are there any valves under the boiler (on the 22mm pipes) ?

 

[Darren Jackson]

1, Yes you could do with an additional expansion vessel.

2, No it would not normally cause the system to loose pressure.

Is there a constant drip or running water coming from the condensate pipe? I've had a few glowworm SXi heat exchangers fail and one of the symptoms is loss of pressure.

How often is a top up of pressure required?

 

[Trevor C]

.... are there any valves under the boiler (on the 22mm pipes) ?

This is what is under the boiler if it helps ...

 

[Trevor C]

Is there a constant drip or running water coming from the condensate pipe? I've had a few glowworm SXi heat exchangers fail and one of the symptoms is loss of pressure.

How often is a top up of pressure required?

Unfortunately I cant tell if there is a constant drip or running water from the condensate pipe because it goes through the wall and is joined directly into a guttering downpipe.

I'm having to top it up every 4-5 days at the moment.

 

[ShaunCorbs]

Turn the boiler off

Turn the red valves off left and right

And leave it for a day

If the pressure drops it's inside the boiler if it doesn't it's on your system