Overflow from Cold Water Tank in Loft All aspects of plumbing questions and answers, help, tips and information

[MargieLondon]

I live in a Victorian house converted into 3 flats, one on each floor. There is a cold water tank in the loft above the 2nd floor. It serves only the toilets on the 1st and 2nd floors.

When this tank is not drawn on regularly ie the toilets are not being flushed much, a fault causes the tank to overflow. A plumber told us some years ago that the fault could not be corrected except by replacing the whole tank. The trapdoor into the loft is too small to remove the tank. The stairs up to the 2nd floor flat are also narrow and have many twists and turns. the plumber advised that a section of roof would need to be removed.

The problem is now becoming quite bad. Can anyone advise? We do not have that much money

MargieLondon

[Barry Bunsen]

Hi
Usually when an overflow behaves like this it is because the ball valve is not stopping the water flow completely and letting just a small amount of water through. If the toilets are flushed regularly the excess water never reaches the overflow pipe. If they are not used the water continues to fill the tank and eventaully overflows. I cant see why you would need to change the tank in this case - just change or possibly clean the ball valve assembly.
Of course there may be a different problem I have not considered. If your not able to examine the ball valve yourself (they're relatively inexpensive) I'd get a second opinion.

[MargieLondon]

Hi
Usually when an overflow behaves like this it is because the ball valve is not stopping the water flow completely and letting just a small amount of water through. If the toilets are flushed regularly the excess water never reaches the overflow pipe. If they are not used the water continues to fill the tank and eventaully overflows. I cant see why you would need to change the tank in this case - just change or possibly clean the ball valve assembly.
Of course there may be a different problem I have not considered. If your not able to examine the ball valve yourself (they're relatively inexpensive) I'd get a second opinion.

Hi Barry
The exact way it was described to me was 'When the water tank is not being drawn on regularly, the arm of the float sometimes drifts over from one side to the other at the point where the arm connects to the ball valve. This can cause the ball valve to let in a drip of water leading to overflow'

[Perry525]

Take a trip to B&Q or similar and look at a ball valve.
They have changed little since they were invented.
They are very simple things.
A ball on a metal arm is lifted by the water in the tank and it presses a rubber pad against the nozzle thereby stopping the water from coming out.
Over time the pad wears and water dribbles out and the small pad need replacing.
These pads cost a few pence and are easy to install, you can do it.

[plastic_man77]

@ MargieLondon

Two questions:

1) Do you consider the mains pressure to all three flats to be quite good? ie. you get more than just a dribble from your taps.

2) Does the cold feed tank in the loft just supply toilets, or does it supply baths, basins or more importantly, showers with balanced hot and cold feed?

If the answer to Q1 is yes, and to Q2 is yes (not balanced feed showers), why not connect the riser main to the storage tank, to the feed from the tank. This would change the inlet to the toilets from gravity to mains.

The only problems you may encounter in doing this, is the float valves in each supplied toilet may be set up for use with gravity feeds, causing the toilet to be noisey when filling or, if the diaphragms or washers are worn in the float valves, the higher mains pressure may lead to the valves passing water when it is supposed to be closed. This can easily be remedied by changing the float valve, making sure it is suitable for mains, or by servicing the current float valve, replacing diaphragms, washers or seals.