Overflowing Tank

[dan77714]

Hi all
I have a problem with my tank in the loft.
Whenever I take a shower it overflows and releases water into my garden. At first I thought it was the a problem with the float however when I went up into the loft whilst the tank was overflowing, the float had stopped the water comming out of the ball cock system therefore the water seems to be comming from somewhere else and filling the tank but I have absoloutely no idea where. The tank overflows ONLY when I have a shower and not at any other time at all. I do not have a water cylinder and the boiler I have is a Combi boiler.

Any ideas? Thanks in advance.

 

[Alz0r]

worth checking - because I've seen this before....

make sure the spout on the float valve isnt discharging near the overflow pipe itself!

I had a customer who's tank's overflow pipe was right next to the valve and water was getting into the overflow when the tank filled!

 

[dan77714]

Thank you for your reply.
I have already checked the spout and it doesn't seem to be discharging any water when the tank is overflowing because the float stops it so the water seems to be coming from somewhere else. the spout is also away from the actual overflow pipe.

 

[dan77714]

Is it possible that water may be coming back up from the boiler and back into the water tank for some reason?

 

[SpecialK]

Do you have a mixer valve? Is cold side on mains water or tank?

 

[dan77714]

I dont think so. where would I find the mixer valve?

 

[SpecialK]

On the shower, what do you use?

 

[stardanny]

Mixer valve is part of shower. High pressure Hot water from combi is pushing back low pressure cold water into tank causing overflowing.

Do you have a shower hose that connect to bath taps?

Dan.

 

[SpecialK]

Erm not sure he has a combi, its more likely to be mains cold flowing through the mixer valve and back into the hot water tank. This causes the hot water tank to overflow into the cold header tank.

 

[stardanny]

I do not have a water cylinder

He does not have a cylinder. hot water from main via combi is pushing cold water fed from storage tank.

Dan.

 

[SpecialK]

Clearly I need to learn to read!
Get a plumber in to to convert everything to mains...or fit some check valves.

Bit strange leaving a tank in the loft?

 

[dan77714]

Thank you for your replies.
The shower and tap I use is similar to this one:


http://www.wickes.co.uk/invt/148366 and yes i do have a combi boiler[/wiki]

 

[dan77714]

is there any way of fixing the problem without getting rid of the tank?

 

[stardanny]

Yes. Connect the bath cold tap from main and still keep the tank. check valve on cold pipe from tank would not work as high pressure hot water will still stopping cold water coming in.

Really all cold taps should be straight from main as you have a combo.

Dan.

 

[dan77714]

would changing the actual shower tap make any difference and if i were to have a check valve fit, where would i have to fit it?