Unvented hot tank - maintenance / servicing

[pooksahib]

Hello. My parents have a 9 year old Santon Premier Plus and recently noticed the water seemed a little hotter than usual. They phoned a plumber who suggested a thermostat fault was the cause and so sent round an electrician colleague of his. (The electrician confirmed the stat to be working and offered - but didn't recommend at this time - a replacement.)

I had a look at the paperwork from the original installation and saw that there was a Service Record Log Book which said the system should be 'serviced regularly' (but didn't say how regularly). I'm surprised that neither the plumber or electrician mentioned 'service' to my parents. Just how necessary is it with this kind of tank and what would a service involve? Thank you.

 

[muggles]

It should be done annually - failure to do so invalidates the 25 year warranty. People usually get them done at the same time as the boiler service. A service should follow manufacturers guidance but generally includes a test of all safety devices, check/recharge of expansion vessel, and check that the water temperature is achieving the setpoint

 

[picasso]

More likely to be a stuck 2 port valve.