DIY Doctor UK DIY Forums

The system:

Open vented, fully pumped Y-plan system, Indirect hot water cyclinder.

4 rads upstair + cylinder, grundfos pump, 3 port valve in airing cupboard
5 rads downstairs + potterton suprima he 30 in kitchen
F/E in loft.

For a while now I am getting air accumulating in the master bedroom radiator. I am having to bleed it once a fortnight. As far as I can make out it is the 3rd rad on the system upstairs which seems to consist of two branches both of which extend downstairs (back + front of house). All other rads are fine and dont even really need bleeding year on year.

Water colour coming out of rads when bled is clear and the F/E water is brown ( I dont believe this is a problem?)

I have dosed in some sentinol x100 as a precaution.... the F/E tank doesnt seem to be the culprit (feed or vent don't seem to taking on air) and the pump does its job as far as ciculating the water is concerned although I don't know how to distinguish if this is the cause of the air.

The feed and vent are piped correctly before the pump & m/v and there is even what I think is an air separator between the two........so basically I am at a loss as to where this air is coming from.

No signs of a water leak, but surely the water must be going somewhere? I am also concerned about corrosion, the last thing I need is the cost of a new cylinder.

Double check for leaks below that radiator, check rad valves and pipework, the slightlest weep could be enough to lose water and as the rad vent isnt open the water cannot be replenished.

If the pump was drawing in air I would expect this to affect more than one radiator.

htg

Thanks for your reply htg

There is definately no leaks above floor level on that rad - unless it is a microleak too small for water....... the pipework under the floor is all soldered and no compression joints apart from the actual rad valves above floor.

I know this as I have had the floorboards up before and there was no ACTIVE leak that I could see although there were signs of previous.... in fact when we moved in I replaced this rad as the bleed nipple had rounded off and rad full of air (possibly pinholed causing previous?), I did this in aug 2008.... I suspect that this has been happening for a while due to the rounded off nipple due to lots of previous bleeding!!

Now new rad is doing the same. Help!

any other thoughts anyone?

I'm thinking that the effected rad is probably the highest in the system which is where the air (or possibly hydrogen gas) is accumulating. Have you put in any X400 to give it a clean? Although the water may be running clear theres a fair chance that the bottom of the rads contain sludge thats generating the gas.

Let it run for a few days (you can actually leave X 400 in for a few weeks), drain, refill, drain, refill until the water is totally clear.

The add your X 100 on final fill, clear all airlocks and rebalance the system.

If you are sludged a more certain alternative is to take all rads off after X 400 treatment, take outside and flush each with mains. Can be a bit messy though. Powerflush is an alternative if you are certain its sludged up (good grief don't let BG do it!!!)

Can't see your last post yet so not sure if this is covered.