Expansion vessel problem

[johnny2007]

Hi everyone,
My son's flat has a combi Worcester Bosch 24i junior which is losing pressure every week or so.
He has been naughty and didn't have it serviced for the past 3 years.
I've been trying to get a boiler technician out for him as he's out 9-5, but the best I got was "i see you in a couple of weeks, keep topping up".
My regular guy is doing a big project down the coast, so no luck there.
He suggested to try and check the pressure on the expansion vessel and possibly top it up.
The valve is accessible at the top without dismantling anything and I have a small digital compressor.
Is he right that I can do it myself until he comes back next month and services the boiler?

 

[terryplumb]

Do you know the correct procedure ?
It's not as simple as just connecting a pump.
What does pressure rise to when heating is on ?

 

[muggles]

Yes, you can do it yourself. You need to connect a hosepipe to a drain point and drain the pressure out, top the EV up to 0.7 bar, then close the drain-off and repressurise the system

 

[oldbuffer]

1. Provided you can access it without removing the boiler case, you can check the expansion vessel yourself:
1a. Turn the system off and unscrew the valve cap.
1b. Very briefly depress the Schrader valve - same as a car tyre valve.
1c. If more than a very small amount of water comes out, the vessel is damaged and needs to be replaced. Gas safe job.
1d. If only air, or air with a small amount of water (condensation) comes out, the vessel is probably sound.
2. If the vessel is sound:
2a. Turn the system off.
2b. Drop the system pressure to zero. Highest radiator bleed screw will involve least loss of water, but see below.
2c. Leave bleed point open. If using a radiator, get someone to catch additional water which will come out.
2d. Pump the vessel up. Pressure may be in the installation manual. If not, 1 bar is generally a safe figure.
2e. Replace vessel cap.
2f. Close bleed point.
2g. Re-pressurise system (water) to around 1.3 bar.
3. If the system has been losing pressure because an expansion vessel fault has caused the pressure relief valve (PRV) to open, there is a high risk that the PRV will not reseal. If you get a constant drip from the pressure relief pipe (outside, copper pipe, turned back towards the wall), the PRV will need to be replaced. Again, a Gas Safe job.

 

[johnny2007]

Yes, you can do it yourself. You need to connect a hosepipe to a drain point and drain the pressure out, top the EV up to 0.7 bar, then close the drain-off and repressurise the system

This is exactly what my boiler technician said.

 

[johnny2007]

1. Provided you can access it without removing the boiler case, you can check the expansion vessel yourself:
1a. Turn the system off and unscrew the valve cap.
1b. Very briefly depress the Schrader valve - same as a car tyre valve.
1c. If more than a very small amount of water comes out, the vessel is damaged and needs to be replaced. Gas safe job.
1d. If only air, or air with a small amount of water (condensation) comes out, the vessel is probably sound.
2. If the vessel is sound:
2a. Turn the system off.
2b. Drop the system pressure to zero. Highest radiator bleed screw will involve least loss of water, but see below.
2c. Leave bleed point open. If using a radiator, get someone to catch additional water which will come out.
2d. Pump the vessel up. Pressure may be in the installation manual. If not, 1 bar is generally a safe figure.
2e. Replace vessel cap.
2f. Close bleed point.
2g. Re-pressurise system (water) to around 1.3 bar.
3. If the system has been losing pressure because an expansion vessel fault has caused the pressure relief valve (PRV) to open, there is a high risk that the PRV will not reseal. If you get a constant drip from the pressure relief pipe (outside, copper pipe, turned back towards the wall), the PRV will need to be replaced. Again, a Gas Safe job.

Thanks for the very detailed advice.
Yes, the Schrader valve is visible and accessible without removing anything.
I'll give it a go and hope it just needs repressurising.

 

[ianmcd]

The most important point is to make sure the drain point is open throughout the procedure, you will see why when you start pumping the vessel, you will see a fair bit of water coming out

 

[johnny2007]

The most important point is to make sure the drain point is open throughout the procedure, you will see why when you start pumping the vessel, you will see a fair bit of water coming out

Thanks.

 

[johnny2007]

Update.
Thank you for the detailed info.
It's been a week since I inflated the expansion vessel to the correct pressure, it was on 0.1 bar.
All working fine and boiler pressure doesn't fall anymore.
I added inhibitor as I was there.
Thanks again.