Diverter Valve

[Gasguru]

Your boiler expansion vessel is either failed/flat/low on pressure...they should be checked every year during the service.
Just a 3 year life for that diverter style is quite possible..they are very sensitive to system water quality/inhibitors.
Baxi sell just the cartridge for other models...it may fit the Powermax.
Very few gas installers are willing to touch the Powermax boilers (a past reputation and long flues)...so you are likely to pay over the odds.

 

[Ian1981]

Your boiler expansion vessel is either failed/flat/low on pressure...they should be checked every year during the service.
Just a 3 year life for that diverter style is quite possible..they are very sensitive to system water quality/inhibitors.
Baxi sell just the cartridge for other models...it may fit the Powermax.
Very few gas installers are willing to touch the Powermax boilers (a past reputation and long flues)...so you are likely to pay over the odds.

Thanks. Do you know how much it is likely to cost (approximately) to fix the boiler expansion vessel?

Do I need to flush the system? Thanks again.

 

[Gasguru]

Vessel might just need re-inflating or replacement...can only guess.