Draining hot water question

[AP77]

Hi,

I am replacing my 12 year old shower pump which has a leak.

I have read lots of posts about isolating the hot water so I can remove the hot water feed to the shower pump but am still a bit confused (note: isolating valve on the flexipipe is not working properly).

So far I have:

1) Closed off the red wheel gate valve where the cold water feeds into the bottom of the hot water cylinder in the airing cupboard
2) Run the hot water tap in the bath
3) After a few minutes the hot water from the bath tap turns cold

I thought by closing the red wheel gate valve to the bottom of the hot water cylinder, once the hot water was all gone, the water would stop from the tap (due to pressure in the system), but it doesn't. Just cold water comes out of the hot water bath tap. I left it running until I have almost a full bath of cold water but it still doesn't stop (until I turn off the bath tap).

The central heating was running at the time, the hot water was not.

I can bung the cold water outlet from the tank in the loft but I am assuming the red wheel gate valve is doing the same thing, i.e. closing off the cold supply to the cylinder.

I have clearly missed something obvious but am not sure what. Hopefully someone can put me straight!

Many thanks, very grateful for any advice, DIYNOT Forum is so incredibly helpful!!!

 

[terryplumb]

Gate valves are junk ! They don't close even though you think its closed to off,it isn't. Pics of your cylinder and valves may help .you may have closed the wrong valve ?? Is your cylinder actually full of hot water ,or is it cold ?

 

[AP77]

Hi Terry, many thanks for replying.

Here is a photo of the cylinder. It is the red gate valve in the bottom right corner that I have turned off. It was fairly tight and I had to hold the red wheel lightly with some pliers to turn it. It turned 4 full rotations.

The cylinder only had a little hot water in it as the bath had been used earlier in the day. The water hasn't been heated since. When I opened the hot bath tap while trying to isolate the hot water, there was some warm water to start with then it quickly became cold.

1) Do you think I may be better off putting a bung in the cold water tank to stop the hot water cylinder from refilling?

2) If we have already used all the hot water from the tank, how much water would you expect to come out of the hot water bath tap before it stops?

Thanks again.

 

[terryplumb]

Think you have closed the wrong gate valve. Those two pipes look to be from the boiler to the coil .have a closer look around the cylinder ,other side or at the back for another pipe low down. When you close the cold feed to the cylinder ,and turn on hot taps to drain out ,you don't actually empty the cylinder .only what's in the distribution pipework ,which is minimal ,maybe a litre or so.and use a downstairs hot tap ,as well as the bathroom hot to empty out the pipework. And yes you can use a bung if you are confident with that method.

 

[echoes]

Are you positive that gate valve is on the cold water inlet to the cylinder and not the cold end of the coil?

Edit: Too slow

 

[AP77]

Thanks guys for trying to help me.

I have looked underneath the cylinder and reached round the back as far as I can but cannot see any other pipes low down feeding in.
In the picture, the higher of the 2 pipes going into the cylinder (half way up) comes from the motorised valve.

Attached is a better picture.

I can see a drain cock which comes round the back and is to the far left in the picture at floor level, but I don't think I want to drain the whole cylinder do I?

Sorry for so many questions....from your replies above, I thought there would only be one feed to the coil in the cylinder, from the motorised valve pipe.
Why is there a cold feed to the coil too and where does it come from?

 

[echoes]

The coil has 2 ends, otherwise no water would be able to flow through it.
The cold inlet is probably on the opposite side of the cylinder to those we can see in the photo. I.e right where it can't be seen. Follow the pipe back from the drain cock and you'll find it!

 

[terryplumb]

Inside your cylinder is a copper coil and the two pipes are attatched to it.hot water comes from the boiler thru one of those pipes ,runs thru the coil , and comes out the other pipe and goes back to the boiler for re heating. So its like a coiled immersion heater ,if you like. The hot water running thru the coil heats up the cold water surrounding it in the cylinder ,and hey presto you have domestic hot water. You need to look more carefully to find the cold feed from the loft tank to the cylinder ,it must be toward the rear.

 

[echoes]

 

[AP77]

Many thank guys, I like to try and understand how things work!

Good idea about trying to follow the drain cock back, assuming the inlet is in the same place. Unfortunately though none of the cylinder on the left hand side is accessible as it is very close to the left side of the airing cupboard. As for the rear of the cylinder, I can only access the right hand side.

I can only assume that when the house was built, they assumed that anyone wanting to isolate the cold water to the cylinder would be done by isolating the water in the tank in the loft.

....there is a cold water gate valve on a pipe running down the back wall of the airing cupboard which I have closed before to turn off the cold taps, but is it possible this would also close the cold supply to the cylinder? It runs down behind the cylinder then straight through the floor of the airing cupboard.......best thing for me to do is close it and find out, I guess.

Appreciate you taking the time to help, thank you.

 

[terryplumb]

You may be able to isolate the cold feed to the hot water cylinder ,at the loft tank. Any gate valves up there ? Unlikely that the cold feed to cold taps also feeds the cylinder.

 

[echoes]

Behind your cylinder will be another pipe coming down from the cold water cistern which *should* have a valve on it. This is what you're looking for. Might have to rummage through your towels to see it.

 

[AP77]

Great, thanks for all the info.

I have now found the cold pipe that comes down from the loft and into the bottom of the cylinder. It is tucked right behind the cylinder, can`t see it going into the cylinder bur l can feel it. Following the pipe back upwards, there is a gate valve which has no wheel on it, which I assume has broken off.

So I think my only option is to put a bung in the cold water tank which will presumably shut off the cold water supply to everything including the cylinder.

 

[echoes]

You could 'borrow' a wheel from another gate valve. They are held on with a nut, but you don't need the nut just to turn it on or off.

If you use a bung, there should be at least 2 (possibly 3 since you have a shower pump) outlets from the cold water cistern. 1 to cold taps, 1 to cylinder inlet, 1 for shower pump.

 

[AP77]

Excellent thanks.

From memory, I think that the person who fitted the original shower pump couldn't budge that isolation valve and ended up breaking the red hand wheel. So I guess even if I borrowed another wheel I will not be able to turn it.....we live in a hard water area which presumably has caused these to seize up.

Anyway, thanks for the additional info about the various outlets in the loft tank, I will make sure I bung up the right one.