Can anyone help out ?

Basically, the pipes are making "knocking/ tapping" sounds when the central heating is on. I've bled the air from the radiators but there seems to be air coming into the system from somewhere as I'm bleeding the air practically every day. Only in the upstairs radiators tho.
But it's the noise from the pipework which is driving me mad.
Is there any other way I can tackle this ?
I quickly read a DIY book on the shelves and it mentioned that there is another valve (in the attic?) which I can bleed and then top up the tank with water ?????

Appreciate any help to save my sanity !
;)

Limited knowledge here, but assuming it's an open system with a header tank... Your heating should have a small header tank up in the attic to keep everything at the right level. It will have a cold water feed and ball valve to keep everything at the right level, plus a vent pipe bent over and hovering over the water in order to let air out of the system. Air should largely find its own way there thanks to the weight of water...

...if it isn't to my mind it means there's a blockage somewhere. Have you got any radiator valves closed that could be causing the problem?

If you could describe the system (combi boiler / vented hot water with cylinder / ...) and any other bits (3 way valve, control, ...) then perhaps someone with more knowledge can give you some help. Have a look to see if you've got a small header tank for the heating for starters, and then work down from there :)

check all the radiator connections, I had air coming into my system, turns out it was from a downstairs cvalve connection that was leaking.

Did have a similar problem once, it was finally traced back to one of the pipes moving ever so slightly (as it expanded/contracted)under the floorboards where it passed through one of the flooring joists. My friendly neihghbourhood plumber fixed it by wrapping a bit of cloth round the offending pipe at that point. Hey presto! no more knocking.

Yep - sounds like pipes under the floorboards expanding and making a noise as they move against the woodwork.

I have this, but there is no way I'm removing the floorboards to clip the pipes down etc

I share your annoyance though!

This is two problems by the look of it -

1 - why are you getting air in your radiators
2 - why are your pipes knocking

I'd guess the knocking is due to expansion as above, but it'd be worthwhile sorting out where the air comes from whilst you're at it...

not an expert on this but having a similar problem with ours. have bled all of the radiators and am pretty confident it's not air - I think it's down to dodgy rusty water in the system (when i had the boiler serviced the engineer said we need the water draining, the system cleansing and then water putting back with an anti-corrosive additive. haven't got round to it yet but .....

G

which reminds me, we have a radiator that only heats at the top (go figure)....

sounds like a expansion noise.
caused when pipes are too tight in the joists and are touching the wood.
you have to take all the boards up where the pipes are run and either cut a bit more of the wood away or put some packing under/at the side of the pipes.cardboard,underlay etc.
if the pipes are tight where they come out of the floor to the rad then this also makes the tapping/clicking noise.you need to make the hole bigger using a fine saw,BUT DONT CUT THE PIPE!!!!

SN

Ok, thanks for all the tips.
However, last night and this morning, the problem wasn't as bad (as in the odd knock/ tap rather than the constant)

I'll have a scout around the attic at the weekend for the header tank, however my floorboards in the bedroom are giving me major headaches creaking so if I get a joiner in to lift and shore them up properly, I'll attend to the pipes underneath at the same time I guess.

Continuous air in the pipes may turn out to be hydrogen! Old systems that have certain internal corrosion can lead to water being converted to oxygen and hydrogen.
Try lighting the gas next time you bleed it - but watch out for eyebrows :)

Nick

forgot to mention,
when venting rads do it with the system(c/h,h/w) switched off.
on a lot of systems if you vent rads with the pump on it can draw air into the system.


Duncan

Ah. Gotcha.
Oh, and I think I've traced it to dodgy floorboards/ joists in the bedrooms. They're making a heck of noise when you walk on them.
Does anyone know if this stuff will be covered by NHBC ?

How old is your house as surely any house covered by NHBC would have chipboard fitted,also the NHBC warranty works on a sliding scale with faults like yours only covered in the first two years and only major structual faults covered at the end of the 10 year period.

Mog

Hmmm..
The house was built I think in 1998.
I'll check out the paperwork this weekend to see what's covered.

Another tip for noisy floor boards and to stop the noise pipes make when expanding is to lubricate them with talcum powder - it should make the floor boards move quietly against the nails and eachother, it should make the pipes move quietly amd smoothly when they expand.