On 17/08/2018 11:22, The Natural Philosopher wrote:
On 17/08/18 11:18, GB wrote:
On 17/08/2018 09:34, The Natural Philosopher wrote:
On 17/08/18 08:32, GB wrote:
On 17/08/2018 07:50, The Natural Philosopher wrote:

Once the cold feed to the cylinder is shut off, you will still get
several litres of hot water out. However let it run and that will
reduce to nothing as the pressure vessel de-pressurises.

Until someone flushes a loo...

then the loo will allow air into the cold side of the systemÂ* and
the hot water will all come out.

Not in my experience, but in theory the head of water within the
pipes could push a small amount of hot water out of the cylinder.
There's nothing wrong with TNP's theory, so I guess it's stymied by
anti-syphon valves in the toilet cistern.

Just to be on the safe side and to avoid an argument with TNP, leave
the hot tap open and flush all the toilets in the house before
changing the washer.

it critically depends where yoy turn the cold feed off. If itÂ* is at
te tank, all well and good.

I turned off the whole house supply. My tank is in the loft.

I thought most unvented DHW is direct from the mains? Our entire house
is supplied direct from the mains, and we don't have a tank.


Most may be, ifÂ* they use a combi.

I have a pressurised HW tank andÂ* its in te loft.



I had drained the hot tap and was working on it when my ex wife
decided to have a pee.

I'm not sure I get that. You would have had to turn the mains off then
run all the water out of the cold water tank. If you didn't then I
don't quite understand what you meant by 'drained the hot tap'.

I dont have a cold water tank

What stopped the hot water running out of the hot water tank was the
partial vaccuum formed by shutting off inconing mains.

Still don't get it

When that sealÂ* was broken, more hot water ran out.

So not the whole tank, just the water stored in the pipes.

And turned on the cold tap as well.

The tank emptied all over me, the floor, and the room below

How annoying.