Cold water expansion vessel failure

GabiW14 · Nov 3, 2015

The cold water expansion vessel (24l) of a three-year-old system has failed and my plumber says that it must be because it was too small for the 300l hot water tank and proposes to instal an additional vessel for safety (as well as replacing the failed vessel). The manufacturers (Geminox) say this is not necessary and that adding an extra expansion vessel will not make a difference to the resilience of the system. Any views?

Also should I buy the vessel from the boiler manufacturer or are these things standard and I would be ok to go with another (cheaper) trusted brand?

Cheers

gassafe · Nov 3, 2015

24 litre seems the norm for a 300 litre tank.

It probably failed because the vessel pressure was not checked & recharged where necessary evey year!

Best · Nov 3, 2015

You must only fit a potable expansion vessel that the unvented unit manufacturer recommends, or they could walk away from the warranty. You should be able usually to obtain the same vessel from a merchant and not have to buy from manufacturer. A larger vessel will do no harm and manufacturer will probably not object, but I can't see why your plumber would insist on increasing the original spec.
As above^^, I am thinking the vessel has been neglected

Riley · Nov 3, 2015

Ps do not fit yourself you must be G3 qualified

chris watkins · Nov 3, 2015

Any new vessel needs to be adjusted / set to the correct pressure before the system is turned back on.

Vessels are supplied over charged for most applications if it is over pressured it effectively reduces the capacity (size) of the vessel.

You don't have a secondary return (circulation pump) system installed, do you? as it is a large cylinder.