Recharging potable water expansion vessel

[Matt887]

I'm g3 register just wanted to check when recharging a vessel on a invented cylinder to 3 bar, as long as the diagram isn't at fault I only need to open a hot tap to drain system and leave open when I test the pressure and recharge there need to remove the vessel

 

[Johntheo5]

If the bottom of the EV is above the top of the UVC, shut cold water supply to the UVC, open hot tap to depressurise, break and disconnect the outlet from the EV, re pressurise, (pre charge) to 2.8bar. If bottom of UV below top of UVC carry out similar procedure until HW stops draining, then break EV outlet and drain the UVC until water stops flowing from the EV, then disconnect and re pressurise, as above.

 

[Matt887]

Thanks it's the expansion vessel is above the uvc. And tap is open. Do you definitely need to disconnect from the cold supply to truly get the correct reading. Or would opening the tap be enough

 

[Johntheo5]

Disconnecting at the EV confirms that there is no water in the EV but reasonably OK to assume if not disconnected.

 

[polesapart]

I only need to open a hot tap to drain system and leave open when I test the pressure and recharge

Yes, simple as.

 

[Matt887]

Thanks and then the pressure reliefs are they abit pot look whether they reseal after the EV reset? PRVs on boilers can be an issue do to sludge etc stopping them from resealing.

 

[Madrab]

Not so much on a potable water cylinder - given they tend to be nice and clean.

Older ones may be a bit twitchy as the rubber seals can harden over time stuck on the seat. Most expansion PRV's are on the cold inlet so aren't subject to much in the way of heat that can also cause problems - the T&PRV's can be a bit temperamental sometimes though as they do get hotter, usually cycling them a number of times can get them to sit back down properly, If they haven't done so after a number of tries then it's time to replace.