How to drain hot water

[domiles1]

I need to replace a hot tap in my bathroom so need to stop the flow of water. I have a fairly old hot water system - a tank in a cupboard upstairs, heated by a boiler downstairs. Do I need to just turn off the mains water and drain all the hot from the tank or is there likely to be a valve or tap on the outlet of the hot water tank?

Thanks

 

[diamondgas]

Hi domiles1 :welcome: to the forum

Usually you'll find a valve on the supply pipe from the tank above the cylinder/in the loft.... It's fitted to the pipe that goes to the bottom of the cylinder and usually situated above the top of the cylinder, height wise! Could be a red roundish handle or an older brass 't' bar handle!

Turn that off, open a hot tap and wait for the water to stop running or at least reduces to a manageable trickle Hope that helps ... If not take a picture of the valves in the airing cupboard and post it up her... We'll direct you that way

 

[Simon F]

:welcome:..:iagree:..but first check that there is not an isolation valve fitting to the tap you want to swap, that would simplify things.
If not then as Diamond says, but also open a hot tap downstairs to empty the pipe work past your tap upstairs.
if the gate valve in the airing cupboard has not been used for ages it may be seized up and you might find it easier to close the cold feed to the attic to drain the cold tank,( but then you use your hot water )

 

[WaterTight]

If you do turn of a screwdriver operated isolation valve under the tap itself be prepared for it to leak i.e. have a replacement ready.

 

[domiles1]

I've found the tap that is in the supply pipe from the cold tank to the cylinder..... it's seized!
So I guess I have to turn off the mains and then turn on taps until the cylinder AND the loft tank are empty??!!!

 

[PlumbBobBob]

if you can get hold of a bung, you could bung the feed for the hot cylinder in the cold tank in the loft. if there is more than one feed from the tank you will have tp work out which you need to bung.

 

[diamondgas]

if you can get hold of a bung, you could bung the feed for the hot cylinder in the cold tank in the loft. if there is more than one feed from the tank you will have tp work out which you need to bung.

That may not be the best way forward to be honest Steveb ... I've known of cylinders collapsing with folk using the bungs on domestic cylinders IMHO

 

[PlumbBobBob]

isn't that when they bung the vent as well?

besides which isn't bunging the loft tank the same as turning off the gate valve on the hot feed anyway? without bunging the vent of course.

 

[SimonG]

I don't mess with the valve to the cylinder anymore. It's off with the mains and run off the hot water. Do what I need to do and add an iso valve under taps for next time.

 

[diamondgas]

isn't that when they bung the vent as well?

besides which isn't bunging the loft tank the same as turning off the gate valve on the hot feed anyway? without bunging the vent of course.

Not on domestic cylinders Steve .... You can do it with the heating f&e coz the copper is stronger grade ... Cylinders collapse under atmospheric pressure unless they're unvented Bunging the feed in the tank is the same as turning off a valve of course

 

[domiles1]

Now I'm worried! This whole collapsing scenarioo - its not likely to happen through just draining all the water out is it?

 

[diamondgas]

Now I'm worried! This whole collapsing scenarioo - its not likely to happen through just draining all the water out is it?

Nope Only if you block off the feed and vent pipes then try to drain it down Not something you'll be doing

 

[PlumbBobBob]

:iagree: don't bung the vent pipe and you will be fine

 

[domiles1]

There is a pipe going from the TOP of the tank and it goes up into the loft and finishes just above the cold water tank - is this the vent? And as long as I dont block this, I can happily block the cold water feed to the tank and empty it??

 

[PlumbBobBob]

yes that's correct

 

[Osborne_Cox]

Just wondering if there's a way to "unseize" that gate valve in the airing cupboard? I've got a similar job, similar problem (do they often seize?). It doesn't want to move at all.

Click for large view - Uploaded with Skitch

Sorry about weird picture of gate valve. Just want to make sure we're talking about same thing, and see whether there's a way to unlock this kind.

Thanks in advance for any advice. This forum looks great.

 

[Simon F]

you can loosen the gland nut slightly to see if that helps,
try some lubricant spray
then just keep putting the pressure on forwards and back,
usually you can get it going but if not drain the tank and swap the valve

yes the picture is of a gate valve and they do seize up due to not being turned for years

 

[Millsy 82]

Turn the mains off drain all of the water, Tank and pipework change whatever you need to swap the valve in the airing cupboard then refill. That way you do not have to worry about water spouting out at you whilst your working.

And fill the kettle as it could take some time.

 

[Osborne_Cox]

Cheers Simon, Millsy...

I'll try the gland nut/spray technique first I think and then move on if/when I have to (just trying to avoid the danger of an air lock).

Thanks again.

 

[gravytrain]

when you drain the tank by turning off the cold mains and running all the hot taps you dont drain the tank in the loft AND the cylinder, just the tank in the loft. the cylinder stays full of water.

this is by far the easiest way, and safest way to avoid any possibility of a flood. at the same time change the gate valve (the red one) in the airing cupboard.

 

[Osborne_Cox]

Cheers.

when you drain the tank by turning off the cold mains and running all the hot taps you dont drain the tank in the loft AND the cylinder, just the tank in the loft. the cylinder stays full of water.

Does that mean an air lock isn't likely?

this is by far the easiest way, and safest way to avoid any possibility of a flood. at the same time change the gate valve (the red one) in the airing cupboard.

Can forced a seized gate valve result in me getting wet?!

Cheers again.

 

[Simon F]

only you know how stiff the valve is and what you comfort level is with the job,
anything is possible, 3 options listed below :-

1- you will get the valve moving and keep it.:hurray:
2- decide it seems to stiff and swap it...:smile5:
3- you try to free it, the valve head breaks of and you get a 50 gallon shower.:cry_smile:

options 1 and 2 are equally likely, option 3 is improbable but not impossible.

 

[jase158]

TBH i stay well away from gate valves, they either stiff or don't shut properly or snap, not worth the hassle of trying to turn off. I still see them fitted these days, am amazed they still fit these.

Only problem is that pump valves are gate valves, the other ones leak or dont work very well.

 

[Rodolphe]

What do you prefer to use instead, Jase158?

 

[PlumbBobBob]

What do you prefer to use instead, Jase158?

probably lever ball valves