Draining hot water tank question

[darren61]

Hi everybody, great site

I'm fitting a new kitchen, all is going well apart from the plumbing which was very kindly fitted around the old kitchen rather than behind it thus needing to destroy the old cupboards to get them out

When I turn the stopcock off obviously the cold water stops almost immediately but the hot has to empty the tank, do I just run all the hot water off from the kitchen tap or should I be closing some or all of the red wheel valves in the airing cupboard.

Is it an urban myth that emptying the hot water cylinder can cause it to collapse in on itself

Thanks

 

[kevplumb]

follow the pipe that goes into the bottom of the cylinder
then turn the valve on that pipe off
then swear profusely cos it dont seal
then drain the cylinder

 

[JPC]

look for a pipe coming down from the cistern (loft ? tank) to the bottom of the hot water cylinder...should have a red, round tap.shut ut.
now cold water should stop pushing hot water out of the top of the cylinder when u open a tap

 

[JPC]

you bloody afganistanian, u beat me too it

 

[kevplumb]

 

[darren61]

Thanks for that

 

[GRC]

If your red wheel valves actually DO shut off the water, then congratulations; I've found very few that do.

Also, if you have a red wheel valve in the hot pipe coming out of the top of the cylinder, then congrats again. One of those in the installation I'm looking at just now would have saved me a LOT of heartache.

Why would a housebuilder fit a gate valve between the cold water cistern and the hot water cylinder, but not one after the hot water cylinder? Discuss.

Regards, Graham

 

[htgeng]

Why would a housebuilder fit a gate valve between the cold water cistern and the hot water cylinder, but not one after the hot water cylinder? Discuss.

Regards, Graham

because they don't have to live there or go back and do maintenance. Every valve costs £££ and they do jobs to price. next question!

 

[ChrisR]

Someone said drain the cylinder. Why on earth would you want to do that? If you shut off, or drain, the SUPPLY to the cylinder the water will just sit in it - you wouldn't be able to get any hot from the taps.

There should most definitely NOT be a tap in the hot water supply from the cylinder unless it's after the pipe going up, which is the vent. There SHOULD be a valve on the exit from the cold water (supply) cistern. Best there is a full flow quarter turn type which shuts properly but doesn't restrict the flow.

Tap/cock/isolating valve type and positioning is not random, it's covered in the usual Standards and Regulations.

 

[felix]

Let's recap some of this.

1) The pipe leading from the cold tank to the base of the hot tank is known as the cold feed. There should be a stopcock or gate valve in it.

2) Stopcocks restrict the flow, even when fully open. Gate valves don't.

3) Gate valves leak. Stopcocks don't.

4) There should ALWAYS be a pipe leading up from the top of the hot tank with an open end hanging over the cold tank. This is the vent pipe. There should NEVER be any kind of valve in it.

5) Hot taps are fed from side branches off the vent pipe. Valves in these branches are optional but unusual.

6) If you really want to drain your hot tank you need a drain cock on the cold feed where it enters the tank. You cannot do it through any hot tap.

7) You can work on your hot water system without draining either tank. Turn off the valve in the cold feed then run a hot tap upstairs to drain the water from the vent pipe only.

8) If the cold feed valve is shut and the vent pipe is blocked, opening a downstairs tap will very likely collapse the tank.

 

[croydoncorgi]

If the cold feed valve is shut and the vent pipe is blocked, opening a downstairs tap will very likely collapse the tank.

And since it's winter time....

If you suspect frozen pipes, do NOT turn on any hot taps downstairs, for the same reason. If the pipes in the loft around the cold tank are frozen, this will include the vent for the hot water plumbing. Running water out of a hot tap downstairs will only take water from the cylinder and with no vent or feed, it will buckle inwards.

And do NOT try to run the central heating if there's any possibility that the F&E tank or pipes leading to it are frozen up! If so, BANG!!

Generally, if pipes are frozen the FIRST thing to do is turn the mains water stopcock OFF. Then carefully investigate to check that pipes / joints have not burst due to ice pressure. With ice in the system, there may not be much or any water leakage. When you heat the building, then the ice will melt and only then will any holes in the system start to leak water.


LAG YOUR PIPES!!!

 

[ChrisR]

5) Hot taps are fed from side branches off the vent pipe

 

[darren61]

I ended up having to replace the gate valve I shut it did what I needed to do then tried to open it again and it just kept turning, I then had to syphon all the water out of the cold water tank in the attic into the bath, cut the old olives off and replace the valve.

As usual a 20 minute job took all morning

 

[kevplumb]

such is life
spech if your a plumber

 

[brumylad]

unlucky.

did you try to replace the valve head gear and use the old valve body.

I have heard that you can plug the cold feed pipe using a bung fron inside the cold water cistern.

If I was doing more of this kind of work I would consider buying or leasing a pipe freezer.