Overflow problem

[ch8rt]

I've had a problem with an overflow pipe from a tank in the roof for a while now. I have two water tanks in the roof, one big and one smaller, I cannot for the life of me work out what the smaller one does. Nothing I seem to do lets the water go downs, other than manually emptying it with a jug.

Anyway, both the tanks have pipe leading into them from the hot water tank (presumably overflows again). This isn't a problem with the larger tank has it gets emptied when taps etc. are used. But the smaller tank is filling up and never getting emptied, meaning its not long before the overflow is going again. I have a constant dripping outside my back door until I get up in the roof with my trusty jug again.

Can anyone help me with my problem, and also what is the smaller tank for??

Thanks in advance for any help.

 

[andy.budgell]

I'm guessing the smaller tank is your header tank for your open vented central heating?

You do have central heating? This is unlikely to ever go down unless you drain your CH.

My guess is the valve that controls the water level in this tank is faulty?

 

[Bahco]

When this tank is cold i.e no heating has been on, the water level should be 100 mm. Adjust if neccesary and see if this solves your prob

 

[ch8rt]

Upon closer inspection the smaller tank is indeed connected back to the central heating tank.

So it looks like I'm going to need a proffesional to have a look at the tank itself, which, although I have never witnessed appears to be chucking water into the little tank everytime it gets turned on.

Apart from when I'm watching it seems!!!! : )

Any ideas where this valve might be for me to have a go myself first and try and save a bit of money??

 

[Bahco]

If you see it pumping over, then you may have a blocked cold feed and WILL need to call someone out to fix

 

[KeithM]

If your CH header tank is overflowing then you may have a hole in the coil which is inside your hot water cylinder.

 

[bathjobby]

But do the obvious first as bacho says; the water level in this F/E tank should be just high enough to cover the feed pipe at the bottom of the tank, so drain the water down to that level and adjust the ball valve to keep it there. That lowers the level of the water in the expansion pipe (gravity is a wonderful thing) and immediately reduces the chances of overpumping. Also the expansion pipe should rise to at least 18" above the top of the F/E tank, again, more room for expansion before over pumping.

 

[andy.budgell]

Mine overpumps as well actually.

But only when the pump stops.

My overflow is nowhere near 18" above the header tank.

My water level is quite low, so I guess some extension to the overflow is necessary.

 

[bathjobby]

Andy, I had the same setup and extended my expansion pipe to around 2 feet plus above the lip of the F/E and it fixed the problem. Overpumping is bad in 2 ways 1) All that heat being wasted 2) (even worse) constant re-oxygenation of water = corrosion inside c/h system and noisy boiler. Not to mention that your overflow pipe from the f/e tank probably drips too...

 

[andy.budgell]

Thanks jobby.
Any reason why I cant extend it with plastic push fit pipework, its a bit easier...?

 

[bathjobby]

Not as long as it is for C/H systems and I haven't seen 22mm in that type. C/H system run at 80c as opposed to domestic hot water at around 55 to 60c.