Expansion vessel

Royellis · Jul 4, 2012

I've got a thermal store heating system. It's unpressurised and the water is heated by LPG. There is a feed tank sitting on top of the thermal store - well, integral with it really - and this is fed via a ball valve. Incorporated into the cold water pipe leading to the feed tank there is a Zilmet expansion vessel, model number Z50. It's about 4" long and about 3" in diameter. It's pressured via a schrader-type valve. This valve has malfunctioned and my only way forward is to replace the expansion vessel. But, and this is my question, is this expansion vessel serving any useful purpose in my unpressurised system? If it isn't, there is no point in replacing it and I'll simply remove it. I hope that someone can advise me.

Royellis

stevetheplumber · Jul 4, 2012

a picture would help but i cant see why youd need it on the feed to a ballvalve unless its there to prevent water hammer unlikley to be a problem as the ballvalve on the heating hardly ever moves you sure its not on the cold feed to the dhw coil as well?

diamondgas · Jul 4, 2012

Royellis said:
I've got a thermal store heating system. It's unpressurised and the water is heated by LPG. There is a feed tank sitting on top of the thermal store - well, integral with it really - and this is fed via a ball valve. Incorporated into the cold water pipe leading to the feed tank there is a Zilmet expansion vessel, model number Z50. It's about 4" long and about 3" in diameter. It's pressured via a schrader-type valve. This valve has malfunctioned and my only way forward is to replace the expansion vessel. But, and this is my question, is this expansion vessel serving any useful purpose in my unpressurised system? If it isn't, there is no point in replacing it and I'll simply remove it. I hope that someone can advise me.

Royellis

Sounds like it maybe there to take up the expansion in the hot water coil of the thermal store Royellis. There's quite a bit of pipe coiled around the inside of the thermal store under mains pressure that'll expand a little 🙂

ahwell · Jul 4, 2012

Sounds like its the small 1 litre potable vessel on the DHW coil - nothing to do with the heating.

Royellis · Jul 5, 2012

I'm not really familiar with plumbing terms but am I right in thinking that dhw stands for domestic hot water? If so, then you may well be right
when you suggest that the pipe supplying the feed tank is also supplying the dwh coil.

I am attaching two photographs which I hope will be helpful. I've removed the defective expansion vessel and temporarily stopped up the hole with tap connector elbow, as you can see. I would appreciate your further comments as to whether or not I should fit a new expansion vessel. Thanks in anticipation.

Regards.

Royellis