Unvented cylinder pressure issues

[Newbie234]

Hi, I am having issues with an unvented water cylinder and just wanted to double check something.

About a week ago I noticed that when the system was turned on there was a dripping coming from the prv and pressure rose to around 4.5 bar. As soon as a toilet was flushed or tap was run the pressure when back down and the dripping stopped.

Plumber has been round and fitted a new cold water prv with a pressure gauge set to 3 bar and pumped up the expansion vessel. I did notice tonight pressure had gone up to 3.5 bar even though the heater hadn’t been switched on (I only switch it on for an hour in the morning).

This is the first time I’ve had an water cylinder (normally had gas etc) however this one has cost me £800 so far as it’s had multiple things gone wrong and literally apart from the tank itself everything else has been replaced.

I just wanted to ask, is it normal for the pressure to rise that much even when the tank isn’t turned on?

 

[king of pipes]

The pressure should be 3 - 3.5 bar at all times the combination valve contains a pressure reducer which reduces your supply to 3 bar this may rise slightly due to thermal expansion but not much more, the expansion vessel should be set slightly lower than 3 bar 2.8 ish to allow for absorbing thermal expansion. Monitor the pressure rise over the next few days . Kop

 

[Newbie234]

Thanks for the advice.

This was the pressure this morning, the system hadn’t been used or switched on all night.

I just have a gut feeling it’s the expansion vessel but would that cause the pressure to rise even if the cylinder isn’t switched on?

Thanks for the response,

 

[John.g]

It won't be your expansion vessel, more than likely the PRV (pressure reducing valve) is passing, these should be "drop tight" can you take a few details off the one fitted?.