DIY Doctor UK DIY Forums

Hi all,
Recently my CH system started making "gurgling" sounds as though air is rushing around the system. I bled all radiators which made no difference. Today I decided to drain and refill the system and went to loft to tie ballcock up and found the header tank contained very hot water. I drained and refilled and then bled the system but still have sme problem. I have turned the pump setting down from 3 to 2 but still same. The bathroom radiatoe which is nearest to pump is filling with air and I can bleed quite a lot of air out of this daily. I fitted an old cast iron radiator to the system about 18 months ago but this has been fine. The system is still performing as in heating rads and hot water but the noise and hot water in header tank is causing me some concern. The system is approx 20 years old. Please help.

Hi,

You need this attending to sharpish.
If your tank is plastic it could collapse along with the ceiling and scalded bodies.
Now, only bleed rads with system off. Turn pump down to 1 and see if that does anything.If not gat someone in.

Hth

The important question is which tank is hot? If its the main Cold water Storage Tank then you need to get immediate help as thats quite dangerous for if that arge tank gets too hot the plastic may fail and you'll have a large amount of hot water coming down.

However, if its the small feed and expansion tank, as I suspect, then you do need to get someone in still but not quite so urgently. You have turned the pump down so that means you have recognised that you have "pumping over" and too high pump speed is one of the causes.

Another cause is incorrect pipework but I suspect that as it was OK before then that isn't an issue. Another frequent cause is a blockage where the feed / vent pipes from / to the F&E tank join the main pipework. That causes hot water to go up the vent into the small tank whence it is dragged back into the system again via the feed. This aerates the water leading to the air problems and also causes accelerated corrosion, reduces system life and may give you boiler problems down the track. The simple solution to that is cut the offending portion of pipework out and replace. Won't take that long.

So my advice is get a plumber in to have a look at it for you asap.

Cheers

Rosebery, Steve, Thanks so much for your time and replys. It is the F&E tank with the hot water in. I'm quite sure the pipe work is OK as I haven't had any probs in the previous 18 years. Any clues on how to find the offending pipe that may be blocked? The 2 pipes from the F&E tank enter (1 cold feed and 1 expansion) the airing cupboard from the loft and then have a tee into one another about a foot down. I have also noticed the boiler only firing up in short bursts, maybe 30 secs to a minute and when the flames go out that's when the noise seems to start.

It will be at the tee you just mentioned.
A tip see if a magnet tries to stick to it!!

[quote="Steve the gas"]It will be at the tee you just mentioned.
A tip see if a magnet tries to stick to it!![/quote]

Thanks Steve, The magnet does not stick. Tunred the heating thermostat right down last night as it's getting warmer and it wakes us up at 5:30am. This morning noise bad as ever as boiler fired up to heat water with heating off. The pipe going to F&E header tank vent red hot. Cold feed going to pump red hot but cold other side of pump. Hot water pipe coming out of cylinder warm. I am now totally confused. Is this still a blocked pipe? Thanks for your help. PS heating was off and rads were cold.

Trace the pipework with the magnet not just in one location. You'll probably find it. I still think you should get someone in.

Cheers