Overflowing Hot Water Header Tank

[David1983]

Hi,

I have noticed that my hot water header tank has been overflowing and venting down the side of my house - I'd like to stop this but can't for the life of me figure out why it's doing this!

Firstly, the header tank is situated in a utility cupboard upstairs as there isn't enough room in the loft (the house is a one-and-three-quarter storey house) so it's very difficult to get a look inside and I can't get the lid off, just lift it up enough to get my hand in.

I have let hot water out and held the float arm up - no water comes in so don't think that's the problem. The hot water cylinder is electrically heated so no extra water is getting in from a heating coil in the cylinder.

The header tank has a cold water in, a connection to the cylinder, a vent and a return loop from the hot water cylinder - could the temperature be set too high and causing this? It's only on 50-55c at present.

I do sometimes notice a hissing when the hot water is off, could the float not be reaching the top (and off) position? Why would it be doing this and how do I fix it? I can't get a look into the tank and have to do everything by feel.

Thanks, David

 

[45yearsagasman]

You're between a rock and a hard place then. It does sound like you need to replace the ball valve and float assy. Very difficult if no access to top of tank.
Cutting a hole in ceiling above tank is one way, or a complete draining of tank and move it to effect repairs.

 

[David1983]

Hi 45years, may I ask what your suggestion is based on? The header tank doesn't always overflow, just sometimes, and I don't know why? Would reducing the water pressure help? I could partially close the stop cock downstairs?

Is there any way I could check to prove that it is actually the float and valve that are at fault here?

Thank you!

 

[JohnD]

have you got any mixer taps, where the cold is mains pressure and the hot is from the tank? these often have an internal leak, especially if they are ceramic taps with a quarter-turn lever or knob.

if it is very difficult to change or re-washer the cistern valve (what idiot built it like that?) you could cut the feed pipe and put in a service valve. If the tank still overflows when the service valve is shut, you'll know there is a cause other than the float valve.

The service valve will also be useful when sooner or later you do have to change the float valve. You might find it easier to fit a new one round the front of the tank.

p.s. depending where the joists are, you might also consider cutting a patch out of the plasterboad ceiling to get your head and arm up.

 

[David1983]

Hi John, thank you for your thoughts! I have no mixer taps at all so the fault is with the header tank. There isn't a service valve although it is going to be something I plan to do in the future, as well as replacing the float valve.

I don't know who put the tank where it is but there isn't any room in the loft for it and the ceiling above it is wood, not plasterboard - the house is a 110-year old croft house in the Outer Hebrides so it's build like a brick outhouse to stand the weather!

As a quick (and temporary) fix, could I bend the float arm down to increase the pressure on the valve, hopefully stopping the oozing and overflowing?

Thanks again!

 

[JohnD]

often there is grit in the valve, if it is a modern quiet one this makes them drip. If it is an old-fashioned one (you mention bending so perhaps it is brass) then the cone and rubber are probably worn out.

have you got a jigsaw to cut the ceiling?

 

[David1983]

I don't want to cut the ceiling as it's also very difficult to get to a osition above the expansion tank. What I'm going to try to do is remove the cylinder overflow from the top of the tank so I can get the lid off then make like a contortionist to replace the valve. Would bending it down help in the meantime? Thanks again!

 

[JohnD]

I rather doubt it. Though by lowering the water level it will take longer to reach the top. I'm also worried you might break something.

if you fit a service valve you can turn it off overnight and when unoccupied (with a pipe slice and compression joints it will be a quick job)