proper way to drain hot water cylinder

tilla tech · 28 Sep 2006

Why is it unsafe to drain out a hot water cyl by running a downstairs hot water tap.
And what is the corret way to drain it if one wants to work on hot water pipe.

Thanks

Softus · 28 Sep 2006

tilla tech said:
Why is it unsafe to drain out a hot water cyl by running a downstairs hot water tap.

It isn't. Why do you think it is?

And what is the corret way to drain it if one wants to work on hot water pipe.

Which hot water pipe?

If you mean a pipe feeding a hot tap, then first shut off the cold feed to the cylinder (or drain the cold storage cistern), then open te lowest hot tap in the house - it will run for a few seconds, or tens of seconds, then peter out.

oilman · 28 Sep 2006

Opening the hot tap will drain water until either the cistern empties, or until a "vacuum" stops the water coming out, if you shut off the cold feed to the tank. You would be able to work on the hot pipe, which will still have water in it, but the HW cylinder will still be full. To empty the cylinder you will need to connect a hose pipe to the drain cock at the bottom of the tank, but you probably don't need to do that.

Softus · 28 Sep 2006

oilman said:
Opening the hot tap will drain water until either the cistern empties, or until a "vacuum" stops the water coming out...

To be pedantic, just for once, it's a little misleading to say that there will be a vacuum, 'cos the water stops when there's nothing pushing it out. Clearly, if a valve is closed on the cold feed then there will be negative pressure below the valve, but even if the pipe were open at the height of the valve, the hot water would still stop with the cylinder remaining full.

Paul Barker · 28 Sep 2006

I belive you now need to be part R registered to drain a dhw via a tap, that's probably what OP has picked up on.

Corgi now run a Part R scheme, membership in the first year is just £500, and it will only cost you £2.50 to notify every instance after a hard days graft, in between getting clened up, having something to eat attending to all the customers messages and emergency plumbing frantic calls.

Probably cheaper just to put a hammer through the cyclinder on the odd occasion you need to drain it, or ask about if anyone knows any Polish who are exempt, because their wifes clean for the judge who lets them in.

Me, I;ll just carry on draining them like I always have, they'll have to prove me incompetent in a court of law before I join their part R scheme.

Softus · 29 Sep 2006

Paul Barker said:
I belive you now need to be part R registered to drain a dhw via a tap

Er, call me stupid, but what is "Part R", and when did it come into force?

corgiman · 29 Sep 2006

Softus said:
Paul Barker said:

I belive you now need to be part R registered to drain a dhw via a tap

Click to expand...

Er, call me stupid, but what is "Part R", and when did it come into force?

oh come on soft you must have heard of it, it has come as a raft of measures undertaken by slick tony and fat gordon to combat the geographically challenged monetary situation that they find themselves in, by introuducing Part R to Z they can rectify this monetary anomaly by moving CASH from your pocket to thiers in one stoke, by insisiting that ALL honest traders HAVE to attend 365 courses a year for ten years to prove that we are competent in something or other (they are working out the finer details of this legislation as we speak)

Gawd Bless Liberty and New fecking Labour

Softus · 29 Sep 2006

corgiman said:
oh come on soft you must have heard of it

Well, you'd think so. But, for the sake of argument, if I hadn't, where would I find information on Part R, and would it say that it had already come into effect, and would it say that I "need to be part R registered to drain a dhw via a tap"?

JohnD · 29 Sep 2006

Paul Barker said:
I belive you now need to be part R registered to drain a dhw via a tap...

I recognise a joke when I see one.

oilman · 29 Sep 2006

Softus said:
oilman said:

Opening the hot tap will drain water until either the cistern empties, or until a "vacuum" stops the water coming out...

Click to expand...

To be pedantic, just for once, it's a little misleading to say that there will be a vacuum, 'cos the water stops when there's nothing pushing it out. Clearly, if a valve is closed on the cold feed then there will be negative pressure below the valve, but even if the pipe were open at the height of the valve, the hot water would still stop with the cylinder remaining full.

It isn't misleading. If you managed to generate a Torr 10^-5 vacuum, atmospheric pressure would still only lift water 34(ish) feet. (At STP). When you shut the valve, water will come out until the atmospheric pressure can hold it in.

Sometimes your pedantry needs controlling. I have said that the water stops coming out when the cistern (and to cover your next pedant's expose (also please note the lack of acute accent over the "e" so you can write some more)) the cistern will include the pipe from the cistern to the level of the bottom of the horizontal run of pipe leading from the top of the hot water cylinder.

You really should get out more to make use of your gorilla grips for compression joints.

JohnD · 29 Sep 2006

I wanna see an equivalent of the "Doctor Who?" joke.

oilman · 29 Sep 2006

I could only find this

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proper way to drain hot water cylinder

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