Header Tank Overflow

[All Mod Cons]

Hi,

I've just noticed a possible problem, which may or may not have been happening for some time....

When our heating / hot water system comes on, after a short time water starts coming out of the header tank overflow. There is quite a bit of water - I can see this as it flows onto a flat roof and the size of the 'puddle' is normally quite large. Also from the growth of moss etc in that area, I reckon it has been happening for a while.

Yesterday I went into the loft and removed water from the tank to take the level down to the point where the ballcock valve just cuts in. This is several cm below the overflow hole. I thought this might cure the problem but this morning after the boiler kicked in to heat the water, the level had risen again and water was flowing out of the pipe onto the roof.

So, not only are we a wasting water, we also may be heating up water into that tank.

Can anyone explain what's happening, if this is the way it should work and if not, how I might fix it?
Thanks,
Richard.

[ProffesorPlumb]

It sounds like that when your water is heating up, it is expanding (as it should do when heated) and spilling outof your open vent into your header tank.

You need to make sure that the vent outlet is min 450mm vertical from the top of the hot water storage tank to allow for expansion.

Try that.

Also, your Central Heating pump may be positioned in the wrong place on your pipework, thus pumping water through through your CH pipework and through your open vent. This could mean that the pump is positioned BEHIND the open vent pipe on your CH pipework (on the direction of flow).

[All Mod Cons]

Thanks for the advice - I'll check this clearance later today, but I'm pretty sure there is more than 450mm difference.

Also, this morning I noted water streaming out (quite quickly) of the over flow pipe for the cold water tank. I noted that water was not coming out of the header tank overflow at the same tme.
Do you think the two problems could be connected in any way?

[bishbosh77]

Is the header tank filling with hot water?

[All Mod Cons]

Yes, the water in the header tank is definately warm.

[bishbosh77]

Sounds like the thermostate to, is the water from the taps very hot compared to normal? if it is thermostates are about £14

[All Mod Cons]

The water from the taps is not exceptionally hot and the boiler cuts in and out depending on where I have the thermostat control know set. I'm pretty sure the thermostat is ok.
Thanks anyway.

[All Mod Cons]

Any more thoughts on this anyone?
My short term solution, though not ideal, was the following...

When the system was completely cold, I removed quite a lot of water from the header tank to take the water level to the point just before the ballcock cut in and started filling the tank up again. I then tied up the ballcock, so no water could enter the tank.
I marked the water level (with the system at cold), and then turned on heating and every hour or so marked the level in the header tank as it rose.
After a while I turned the heating up to full and left it for a while before marking the water level for the final time. At this point the the level was about an inch under the overflow pipe level, but quite a lot higher than the mark when the sytem was cold.

I've now turned the heating off and will monitor the level as it drops down to (hopefully) the first level mark.

As the ballcock is tied it can't let anymore water in if the level falls below the 'cold' level. I'm guessing this is what must have been happening. Then, once the heating warmed up the water and the level rose, we got water coming out of the overflow.

This is not a great solution but will do until I find the proper answer to this pronblem. It saves wasting a load of water out the overflow twice daily as the heating goes on and off.
If anyone has anymore ideas I'd be grateful to hear them.
Richard,.

[MetalMickey]

The F&E tank should only have a splash of water in it about an inch deep.

If your tank is full and the hot water expands 4% then its gonna overflow, so you need tolower the ball arm very low... although may not have grasped your prob

alternatively you may have a primatic HWSV and the central heating has been extended... thus theres always too much water inthe system.

[All Mod Cons]

Hi and thanks for your suggestion.
i did get to the bottom of this problem in the end. It turned out to be a split coil in the hot water tank - so that the hot water system was leaking into the hot water system.

I changed the tank and all is now ok.

Richard