F&E tank overflowing. why ? Oh why ?

David cooper

David cooper

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Please help me, I am admitting failure here.Customer's F&E tank was overflowing when heating was on.
Very old ballvalve, so I replaced it as it dripped every 8 seconds or so.
got a phone call next day. Problem still there so as main cold water tank is higher than F&E tank i suspected the cylinder coil was pinholed.
This Thursday I fitted a new cylinder.
Just had a phone call "it's leaking from the overflow again.

BAXI Bermuda with gravity H/W & pumped C/H.
Boilerstat operating fine. Was pumping over so I raised the open vent from about 1 foot to 2 foot above water level.
Still pumping over. Open vent on flow & cold feed on return.

Any suggestions please, or am I stupid ?
 
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Some suggestions, not suggested as egg sucking:

1. Make sure its the F&E overflow. I once spent hours with a customer's unvented cylinder she said was overflowing. Turned out to be the WC overflow which was right next to it.
2. Hang a container of some sort under the open vent. If it doesn't get water in it, its not coming from the vent.
3. If it is coming from the vent, does it happen with central heating only, or with hot water and CH (assuming you can't have HW without CH).
4. Blocked cold feed?
 
With the pumping over - I had a small amount of water dripping from the overflow - caused by the steam in the f+e cistern condensing in the pipe :eek:
 
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Thanks for the quick replies gents.
It's 100% the f&e overflowing as it's drowning the float !!
System filled up a dream.
will check the pump speed but it shouldn't do it anyway. System is at least 30 years old.
 
Does the Bermuda need an always on radiator as a heatsink for the heat exchanger? Has client just had a bathroom fitted & bathroom fitter has stuck a TRV on the rad in contravention of direct instructions not to (well that's what one did to me. Tit) or has someone wound the lockshield down on it or is it full of air?
 
Could it be that the pumping over is entraining air into the system water, this air coming out of solution at the rads and causing the F&E level to rise?
To be sure it's not the filler that's failed or faulty, isolate the fresh water feed to it temporarily.
 
I came across a Bermuda/cylinder, mid-pos valve setup that had appeared to work fine for 25 years, all of a sudden the F&E cistern would overflow.
Looking at the configuration of the pipework and connections I could see that it was marginal from install date.
A partial blockage caused air to be drawn down the vent pipe filling the nearest rad...pushing the rad water back up to the F&E cistern and overflowing.
As soon as the heating was switched on the rad would half fill with air.
I extended the vent pipe down (use speedfit) and into a bottle filled with water...just so I could turn on the heating to monitor the water level....on switch on the water was drawn out.
A powerflush sorted it although ideally the pipework needed re-configuring but it would have been a pita.

Picture 584.jpg
 
Going with the sludgeing over 30 years causing the problems - maybe the system was plumbed wrong but only showed up when the sludge got to a certain amount :idea: Is there a injector T with the gravity return coming underneath and up into the injector ? The pump should be on the c/h flow somewhere - maybe it's on the return, pumping "too hard" and going up the gravity side then out the vent, as you've seen. Also there could be a spreader on the injectorT setup, to direct the water inside the boiler. Blocked/sludged ? Maybe the vent has always flowed over and now there is air being drawn and collected in rads letting the water level in the f+e drop and fresh water come in = overflow.:unsure:
 
I'm going back tomorrow morning to cap the f&e cold supply . Can't seal the system as no overheat thermostat fitted. Customer is not bleeding rads every week, pump is existing one. I may combine cold feed & open vent.
Perhaps I should get a priest in to exercise the system !
Will keep you updated. Cheers.
 
If you use a combined feed and vent such as an airjec then no need for the Overheat kit.
 
D

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