Hot water in the cold storage tank !?!?!

[LeeroyBrown]

I have noticed a leak from my overflow. Tracing it back it appears to be from the cold water storage tank in the loft. I checked the tank and it was nearly full to the top. I have checked the ball valve which is fine (no leak or drip). The expansion tank was probably only 1/3 full nowhere near its limit and the only other strange thing i noticed was that the water in the cold tank was very warm. Is it possible that for some reason the hot water is backing up from the hot water cylinder somehow. If so how can i adjust this. I have a normal hot cylinder with herculag covering and a boiler downstairs in the kitchen. Please help....

Thanx

 

[keego]

Try checking the thermostat on your immersion heater, you will probably find it's knackered & the cylinder is boiling over through the expansion pipe.

 

[ollski]

which storage tank is higher the heating or the hot water?

 

[LeeroyBrown]

Keego i know my thermostat is working ok. I have turned the isolation valve off on the cold feed into the tank, but it still keeps rising substantially when i turn on the hot taps it lowers the level back to nornal in the cold storage tank. After abou two days its full again and the overflow drips. even when the isolation valve is off.

My cold tank is the same level as the expansion tank they are on the same raised platform in my loft obviously the cold storage is a bigger tank though.

 

[ChrisR]

Somewhere you have a mixer tap with cold connected to the mains. There is a connection (ie a fault) between the hot and cold within the tap, so the mains is pushing hot water back up the pipe into the CW header tank. It's often the kitchen sink tap as the other cold supplies in the house are from the tank. See if the bath/shower cold is mains too (powerful).
You could put a non-return valve on the hot supply to stop this happening.
Whether you need one according to regs depends whether H & C mix in the spout..

Or get a new tap!

 

[cozzmic]

Or you have a pinhole in your heating coil in the hot water cylinder. Is the central heating tank higher than the gravity tank and does the ballvalve on it drip.

 

[ChrisR]

The clue was in the answer Cozz:

My cold tank is the same level as the expansion tank they are on the same raised platform in my loft obviously the cold storage is a bigger tank though.

 

[doitall]

Sorry cozzmic but Chris is right on this .

Shower valve, mixer tap or blender valve.

 

[cozzmic]

I know I know but it's another problem I've come across a couple of times. Similar simptoms, if the F & E tank is slightly higher.

 

[doitall]

Storage tank should always be higher water level than the header tank to stop contaminating the domestic water.

 

[cozzmic]

In a perfect world

 

[doitall]

In a perfect world

Its the norm with all good plumbers

 

[cozzmic]

Yes, I would do that properly but on older installations and poorly installed tanks you come across these problems now and again. (In a perfect world through rose tinted glasses).

 

[Gasman1015]

Came across this same problem only a few days ago, turned out to be the mains cold feed connected to a Bristan shower mixer valve pushing the water back into the tank, the hot supply was on gravity feed, as ChrisR already pointed out.