Hot water going into cold tank

[Shebu]

Hi

I've just had a new combi boiler installed and ever since the overflow from the cold water tank in the loft has been overflowing. It stops when I run my tap so I know that it's my tank (property of 4 flats) We've replaced the ball valve and it's still leaking. When we were up there we noticed little bubbles coming in through one of the pipes and the water rising so we think some mains water pressure hot water is going up to the tank and to hopefully solve this we are going to fit a non return valve so the cold water can come down but nothing can go back up. As I can not access the pipes in my bathroom easily we have to put this up at the tank. Unfortunately my plumber can not come out till the beginning of next week and as the dripping is keeping everyone awake and making the steps next door slippery, I want to try and sort this temporarily during the night and when I'm at work during the day.

If I turn the boiler and the mains cold water off, will this stop any water going up to the loft?

Thanks

 

[andy]

a combi doesnt need a tank... sounds like he has forgot to blank the hot and cold going to it....

 

[pierrot]

8) Iy you have a combi you shouldnt have a cold water tank, it should have been completely disconnected.
Combi boilers take there cold inlet directly from the cold main.

 

[Shebu]

Thanks for your replies.

The cold water tank feeds the cold taps in my bathroom which is where the mixer tap is which I think is causing the problem with the mains pressure hot water. I know I don't need one really but I can't afford to connect the cold water in the bathroom to the mains at the moment.

Will turning the cold water mains and the boiler off stop the water going up to the cold water tank?

 

[pierrot]

8) sounds very strange having cold water tank fed.

 

[Shebu]

The cold water to the boiler comes from the mains. It is just the cold water in my bathroom that comes from the tank.

Being that I can't disconnect the tank this evening, will turning the mains cold water feed off and turning the boiler off stop any water going up to the tank?

 

[andy]

The cold water to the boiler comes from the mains. It is just the cold water in my bathroom that comes from the tank.

Being that I can't disconnect the tank this evening, will turning the mains cold water feed off and turning the boiler off stop any water going up to the tank?

yes, since there wont be any water

 

[Gasguru]

As long as you don't use the bath mixer tap you won't get backflow of hot water up the cold feed pipe to your cold tank. If you have a shower off the bath mixer that probably doesn't work properly.

Get the cold taps (and WC) put onto mains pressure - easy and cheap job. Be prepared for posible leaks on the cold taps etc and you may need to replace float valve in WC (as will be under mains pressure and maybe more noisy)

Don't ignore as backflowing hot water into cold tank could lead to Legionaires disease in the summer months.

Sounds like you employed a cowboy installer to leave your plumbing in this state.