Hi,
Please can somebody help. We have two tanks in the loft, one large, one small. I am not sure what the smaller one does as when we run the bath, flush the loos etc it is always the larger one that empties and refils.

Recently we have been getting a constant dripping from the overflow pipe connected to the smaller tank. So we had the ball-cock and valve replaced. It kept dripping though. The water level is higher than the ball and stays around the level of the outlet hole. We have bent the arm for the ball but it keeps getting submerged in water. I know that the valve is good and not faulty. The two tanks are on the same level.

Any ideas? All I can think of is that water is being pushed back into the tank. it looks like there is a pipe connected right at the bottom of the tank. Could it be coming in from there?

Any ideas?

Thanks

Si

Simon, September 2009

Same problem for us with overflow, but we also had a slow leak from the tank which has caused some ceiling damage. We've been quoted £500 for a new cylinder due to a hole in the coil

jk, October 2009

cylinder coils gone.
isolate the feed to the cylinder dhw and that will test if the f/e is still filling.

hi-spec plumbing & heating (essex), September 2009

Big & Expensive are relative terms and depend on your personal wealth to a certain extent. Copper is expensive on the world market so tank prices will be relatively high.

Avoid British Gas - seek out a small independent plummer locally - an established tradesman with a reputation to maintain - personal recommendation or a small ad in yellow pages - avoid also any Large Brash super dooper outfits.

I am not a plummer and avoid this work as often as possible - I hate water engineering.

I have no absolute confidence in my original answer it's just a logical conclusion and not based on prior experience as I have none.

I would expect perhaps £200 for the tank and maybe £300 for the fitting of it but again I guess.

£500 is a lot of money to spend on a stranger's guess so you need to confirm my uneducated diagnosis before asking for a new hot water cylinder.

Good luck...

P, September 2009

Thanks Peccavi. If I do need a new hot water tank is that an expensive and big job?

Simon, September 2009

The smaller tank is the header tank for the central heating radiators - if the inlet valve is good then water may be entering this small tank through the outlet pipe you mention.

In your hot water storage tank is a heating coil that circulates water from the boiler to warm up either the radiators or the tap water in the tank - a motorised valve decides which way the water goes. Radiators and the coil are topped up by the little tank.

If the coil in the hot water tank has a split or small hole, the water in the big tank has a direct connection with the little tank. Even though the bases of your two loft tanks are level with one another each has a different height of water - with a small hole or split in the heating coil, gravity will be trying to equalise the the water levels of the two loft tanks.

Wait for the overflow to happen - make sure nobody is drawing off hot water - nip up to the loft - test the temperature of the water in the little tank (it should be quite cold) - observe the inlet of the big tank and see if any water is flowing out by the action of the inlet valve.

Alternatively - turn off the boiler and tie up the inlet of the big tank so that no water can enter it and mark the water level - wait. If the overflow stops and the level of the water in the big tank has dropped then there's a hole in the heating coil in the hot water storage tank in you airing cupboard.

You may need a new hot water tank.

Good luck...

Peccavi, September 2009