HOT WATER GOING INTO COLD TANK

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:idea: My brother has had a problem for a while with hot water occassionally going up from the hot tank into the cold tank, not by the overflow but by the pipe that feeds the hot tank. I've been in the loft when it happens and the water is hot and the plastic tank can get soft. Water goes out the overflow. He has had the valve that controls the water/heating/both checked and that is ok and he has had mixer taps replaced. Any ideas anyone please?
 
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Bobthebender. Thanks very much, I've just told him. Do you know why it does not do it continuously please?
 
If he has two tanks in loft and the water is rising up the cold feed of the lowest tank then that is the problem.....coil.
 
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Would check the mixer taps aswell. Have you had new taps fitted, possible a check valve failed.

To prove the coil theory, isolate water supply to header tank and observe water level, it will quickly drop.
 
A failed immersion heater thermostat will do it too.
 
Bob, thanks. Rob, taps replaced already. Not sure how immersion thermostat would cause the problem, wouldn't the overheated water just vent out the vent pipe? This hot water is coming up the cold feed.
 
remus said:
Bobthebender. Thanks very much, I've just told him. Do you know why it does not do it continuously please?


because it probably needs the boiler to be running to open the hole in the coil

bender is right
 
wouldn't the overheated water just vent out the vent pipe?
Yes sorry I didn't read it properly. It might make it to the feed pipe but the vent pipe would be hotter.
Are you using only the boiler to heat the water?
 
bobthebender said:
The coil in the indirect hot water cylinder has a hole in it. :cry:
I don't think it does.

bobthebender said:
If he has two tanks in loft and the water is rising up the cold feed of the lowest tank then that is the problem.....coil.
But it isn't doing that - it's rising up the cold feed into the CSS.

corgiman said:
bender is right
I really don't think he is, cm.
 
Softus said:
bobthebender said:
The coil in the indirect hot water cylinder has a hole in it. :cry:
I don't think it does.

bobthebender said:
If he has two tanks in loft and the water is rising up the cold feed of the lowest tank then that is the problem.....coil.
But it isn't doing that - it's rising up the cold feed into the CSS.

corgiman said:
bender is right
I really don't think he is, cm.

35 years as a lead basher,pipe bender and gas fitter tells me i probably am ;)
It does not matter which tank it is rising into if that tank is lowest then that's where it will go.
You knew that though Softus :rolleyes: :?:
 
I'm with Bob and Rob and CM on this. What's in your mind, Softus?
 
Well, you're all being very kind and patient with me, so I've been back over the topic to see if I've misread something.

Firstly, bobthebender, of course you're right that water will find the lowest point, and that a holed cylinder coil will fill whichever cistern is lower/lowest, and you're right that I knew that. I didn't mean to imply that anyone was wrong about that.

However, the OP is demonstrating a good understanding of the principles involved, and there's a consistent message from him/her that the water is flowing from the cylinder, back up its cold feed, into the CSS.

So, assuming that all of the obvious ball valve checking has been done, it all comes down to the relative heights of the cisterns; if the F&E (water level) is higher, then the cylinder coil is holed/split; if the CSS level is higher, then it can't be.

Given that we're waiting to hear which of these applies, and given that it's commonplace for both cisterns to sit on the same base, I was just playing my hunch card.

It's a risk that I'll be wrong, and you'll then all spank me with basin wrenches and spray my nads with expanding foam, but I was feeling mischievous so I'm taking that risk. ;)
 
remus said:
:idea: My brother has had a problem for a while with hot water occassionally going up from the hot tank into the cold tank, not by the overflow but by the pipe that feeds the hot tank. I've been in the loft when it happens and the water is hot and the plastic tank can get soft. Water goes out the overflow. He has had the valve that controls the water/heating/both checked and that is ok and he has had mixer taps replaced. Any ideas anyone please?

A failed immersion heater thermostat will do it too.thats exactly what happened to me :mad:
 

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