constantly having to bleed rads

[billozz]

hey guys,
hope you can help. i am constantly having to bleed the rads on my htg system and its driving me mad. i am not a plumber but i do know a little about htg systems...i used to sell spares so picked upp a bit here and there. i know that air must be getting in somewhere ...but any easy ways of finding out where
hope you can help

 

[brumylad]

Is it vented (ie expansion tank in the atic)
or unvented / sealed (ie big red or blue expansion vessel in the airing cupboard or inside the boiler-flat disc thing at the back)

 

[kevplumb]

check the rad valves and pump position
would think pump is on return
neg pressure no leak but pulls air in

 

[billozz]

hey there guys
the boiler is a combi, not sure if the pump is on the f or r....checked rad valves no leaks as far as i can tell

 

[kevplumb]

whats the pressure in the system
cold / hot
before the pump starts / after the pump starts

 

[ollski]

How old is the system?...is it a new boiler on an old system?....any inhibitor?...was it flushed when it was installed?. You need to get a sample of the water really, If the sludge is reddish brown it means air is causing the damage if its black then electrolytic corrosion will be doing the damage as a guide. check for leaks first though, if you are frequently topping up the pressure you are adding oxygenated water which releases the oxygen as it heats up which the collects at a bleed point...at the same time it is sludging up the system.

 

[billozz]

just had a look and the pump is on the return....kevplumb, what did you mean by negative pressure pulls air in but no leak
thanks
bill

 

[kevplumb]

if the pump is on the return
the pump is dragging the water round the system (neg pressure)
if the pump is on the flow its pushing the water (pos pressure )
if you have a small leak with neg pressure it can pull air into the system easier than let water out

 

[ollski]

just had a look and the pump is on the return....kevplumb, what did you mean by negative pressure pulls air in but no leak
thanks
bill

Water won't come out but air will get sucked in.

 

[kevplumb]

i just said that I think (altziemers etc)

 

[ollski]

i just said that I think (altziemers etc)

I know but my typing is slow and my inclination to correct myself non existant

 

[billozz]

kevplumb,
i thought you were going to say summat like that. Is there any way to stop the air getting in, i have heard of some kind of leak sealer ...like radweld, but for c/h systems. Would it wrok
regards
bill

 

[kevplumb]

personally detest the stuff but it loves auto air vents

 

[ollski]

Have you checked your water quality yet?