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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> Hot water stops when cold tank drains https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1318576525 Message started by Had99 on Oct 14^th, 2011, 8:15am

Title: Hot water stops when cold tank drains
Post by Had99 on Oct 14^th, 2011, 8:15am

Hi there,

we have a low pressure hot water cylinder where the cold water tank directly from the mains sits above the hot water cylinder. Recently I turned off the mains pressure and drained the cold water tank in order to cap off an old leaking tap in the roof cavity. Since then the hot water runs out whenever the cold water tank empties, this didn't happen prior to this, and since there should still be plenty of hot water in the actual cylinder I'm not sure why its happening. Is there a way to fix this problem?

thanks

Title: Re: Hot water stops when cold tank drains
Post by Natedog on Oct 14^th, 2011, 8:26am

I'm presuming you mean water stops doing out of the tap, and not that you then get cold.water from the hot tap?

This would be normal surely? It's the cold water in the tank that pushes the hot water out of the cylinder. Are you sure you've got the valve you turned off to drain the tank fully open?

Title: Re: Hot water stops when cold tank drains
Post by thescruff on Oct 14^th, 2011, 10:12am

As above, not turned the valve on fully or you have a blockage in the ballvalve.

Title: Re: Hot water stops when cold tank drains
Post by CWatters on Oct 14^th, 2011, 3:41pm

Perhaps some sort of air lock in the cylinder so it's not full?

Title: Re: Hot water stops when cold tank drains
Post by thescruff on Oct 14^th, 2011, 4:19pm

No CW ;D

Title: Re: Hot water stops when cold tank drains
Post by CWatters on Oct 15^th, 2011, 9:45am

wrote on Oct 14^th, 2011, 8:15am:

Since then the hot water runs out whenever the cold water tank empties, this didn't happen prior to this

Clarification required...

What didn't happen before?

a)The hot water didn't run out when the cold tank emptied or
b) The cold tank didn't empty before

Title: Re: Hot water stops when cold tank drains
Post by thescruff on Oct 15^th, 2011, 11:40am

Typical blocked ballvalve or not turned on fully CW