Thermal store expansion vessel on incoming cold is it reqd?



I have a situation with a leak (weep) on the small 2L expansion vessel on a vented thermal store. The vessel is on the incoming cold side (i.e. before the mains pressure cold enters the coil for indirect warming.

Now I have fitted a number of thermal stores before and have seen stores with and without this expansion vessel. I understand that the vessel is there because the water in the coil heats upo and therefore expands.

As some stores have this and some do not - can I just remove it rather than replacing?

Presumably any expansion would just "push back against the incoming mains pressure?
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That looks like a trade enquiry!

It depends upon the volume of the dhw coil. If it less than, I think, 15 litres, you do not need any dhw expansion. If your main stop tap has a completely loose jumper, it can act as a non-return valve, and expansion could be blocked.
1 Aug 2008
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United Kingdom
They act as an expansion and shock arrester. If there is a meter fitted then you will have no expansion down the main.

If it's a kingspan cylinder then I would re-fit a 2l vessel.

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