Feed and Expansion tank overflowing

[Nobby84]

My Feed and Expansion tank in the loft is overflowing occasionally. Not dramatic, just a trickle now and again when the water is being heated. Pretty sure it's not the ball valve. My system is ancient, but it works (mostly !) Does have the tendency to overheat occasionally but |I've never had the overflow problem before. Whats confusing me is that the water in the tank is cold, is that right ? Will bleeding all the radiators help ? Guess I'm going to have to call someone out eventually but I could see them condeming the whole system .....

Is there anythong else i could try/look at before I do that ?

Many thanks for any advice.

 

[Burnerman]

Initially, stabilise the water level in the tank so there is around 4" of water in it, adjusting the inlet valve so no more is introduced......and see if the level increases from there. As expansion takes place with the heating on, the level should rise, then fall again.
John

 

[Nobby84]

Thanks. Adjusting the valve, is that easy ? I have bent the arm of the ball valve down a bit so the tank doesn't fill as much. Still overflowed last night though. Am trying a lower setting on heater control. It's ranged from 1 to 6, anything above 2 seems to be red hot. Mrs. always shoves it on 6 to heat up water, grrr....

 

[Burnerman]

Check to see that water isn't entering your tank from the expansion pipe that curves above it......if it is, then other issues are being pointed at, with a pump speed that is too high being the easiest one.
With the system completely cold, aim for 4" of water, and no dripping from the fill valve at all.
John

 

[Nobby84]

Ok thanks. Don't think its coming from the pipe over the top of the F&E tank, that's dry. Think it must be coming from the feed from the bottom of the tank. Bled the radiators tonight, got a LOT of air out of one of them, could that be the cause ? Guess I'll find out tomorrow

 

[Burnerman]

Obviously in an ideal situation, the rads need to be purged of all air, so after you have done that, let the system stabilise and monitor it from there.
If there's some sludge in the system (black water, meaning magnetite or rust) be aware that this can generate its own hydrogen gas.....a good and impressive test is to see if the gas coming out of the bleed valves will ignite
Not such a bright idea though if the bleed valve surround is plastic
John

 

[Nobby84]

Yes I did get black water out of the radiator (eventually), and brown water when bailing out the F&E tank.. My boiler is circa. 1979, think i'm going to have to face up to the inevitable (!) Like the Hydrogen gas theory, will have to try with a match tomorrow, the kids will be impressed

 

[Burnerman]

Yes I did get black water out of the radiator (eventually), and brown water when bailing out the F&E tank.. My boiler is circa. 1979, think i'm going to have to face up to the inevitable (!) Like the Hydrogen gas theory, will have to try with a match tomorrow, the kids will be impressed

Brown water in the F/E tank is often just rust from the mains, but its a good idea to get rid of it (wet vac very useful here)!
The gas theory does indeed impress the customer.....'bloody 'ell wor lass this lad can burn watter' was a recent comment
John