Tap won't turn off

[Matty F]

We have a 30 cubic metre water tank that has a stopcock at the base in the pipe that goes underground. When the stopcock is turned off, an apparently endless amount of water still comes out of the taps in the building that is supplied. Perhaps the stopcock is not working, but it's hard to dismantle it without draining the tank. The outlet pipe is in the middle of the tank under 3 metres of water at the moment. I could try to use a long stick to put a plug over the pipe, but it isn't going to be easy through a tiny hole in the roof of the tank.

With the stopcock "off", after running a tap for a few minutes, the water gets decidedly warm. This is quite likely to be backflow from the solar-heated hot water cylinder on the roof. Except that there is a non-returrn valve inside the wall to prevent backflow. Perhaps that non-return valve has failed, in which case it means taking the wall apart to get at it.

Having possibly drained most of the hot water tank, when I turn the stopcock "on" again, I can't hear or feel any water flow through the stopcock.

Any guesses what is wrong? The stopcock or the non-return valve? Or both, or something else? I need to know in 12 hours :)

[The Medway Handyman]

Is it a gate valve like this?

a stopcock like this? freezing kits do work surprisingly well, if you have the courage :-) ?_dyncharset=UTF-8&fh_search=pipe+freeze

[Dave Liquorice]

With the stopcock "on" does the water run warm after a similar amount fo time? If not then it indicates that the stopcock is working and there is flow from the solar tank.

[Matty F]

this?

> Or a stopcock like this? guess it's a gate valve: 's the tank: white pipe is for the wires to the float valve at the top. The black pipe is for the water that is pumped up to the tank.

This is the outlet pipe in the bottom of the tank:

Pipe freezing kits do work surprisingly well, if you have the courage :-)?...I think I can devise a conical plug (with a cord attached) that I can push into the overflow pipe using a long pole.

[Dave Plowman (News)]

hard water area. Replace with a full bore valve.

[Andrew Gabriel]

Just to warn that that looks like a tank you could easily drown in if you had an accident, or the top gave way. I suggest you shouldn't work on top it without having one or two other people present with some rescue gear ready.

There are lots of those on stilts in the US, and when I was at school in the US, a child in another class drowned in one when climbing it for fun. I guess the lid collapsed. That was not an uncommon occurrence on those towers at the time, where the height and view looked like quite an attraction to adventurous kids.

[PeterC]

If the distance from the wooden tank isn't too much for the time to warm water flowing, surely the water in it could flow warm if the sun had heated the contents.

[Matty F]

I'll try that tomorrow. The stopcock is some 50 metres from the building so it takes a while to try out ideas.

It's the middle of winter here and the water in the wooden tank is definitely cold. I tested the shower and it is comfortably warm.

[PeterC]

Ah, sorry - not thinking upside down.

[Matty F]

I now think that it's the non-return valve that isn't working and the stop-c*ck is working OK. The shower hot water is taken from the top of the hot water tank. With the stop-c*ck open we get hot water from the shower. With the stop-c*ck closed there is no hot water from the shower. Therefore the stop-c*ck must be working OK. I'll find out when the non-return valve is fixed. There should then be no water at all from the other taps when the stop-c*ck is closed.

[Matty F]

Fixed it today. The non-return valve was not working. The stopcock is working perfectly. When the non-return valve was faulty, if any tap was turned on, that allowed water to drain from the hot water tank, thus water did not circulate through the solar water heater.