Air in system and a filling Header Tank

[2ellett]

Hi there, some assistance and expertise is required.

I have a standard open central heating system which up until recently has been pretty well behaved. Now I having to regularly bleed the same 3 radiators due to the ingress of air into the system.

Coupled with this the small feed / expansion tank tank is now filling through the expansion pipe with hot water. I'm assuming this is where the air problem is coming from.

I've made no changes to the system in the past year other than replacing old radiators with new, like for like.

I'm sorry if this is a repsot. And I greatly appreciate any suggestions, theories and solutions.

Thanks all.

 

[Softus]

Now I having to regularly bleed the same 3 radiators due to the ingress of air into the system.

Coupled with this the small feed / expansion tank tank is now filling through the expansion pipe with hot water. I'm assuming this is where the air problem is coming from.

Possibly. It depends on your definition of "expansion pipe".

One cause of the symptoms you describe is advance corrosion. What's the contents of the F&E cistern like?

Another possibility, is a split/holed cylinder coil - is your F&E cistern overflowing?

 

[gas4you]

Could also be a blockage in pipework which is now causing pumping over which must be sorted asap otherwise it will cause premature failure of your heating system

 

[Softus]

That's the same thing as advanced corrosion.

 

[gas4you]

Take your point

 

[Softus]

Keep your hands off my point.

 

[2ellett]

One cause of the symptoms you describe is advance corrosion. What's the contents of the F&E cistern like?

The F&E cistern water is clear (small amount of sludge at bottom of tank)
I've bled various radiators throughout the house and all water is clear, no black / rust present.


Another possibility, is a split/holed cylinder coil - is your F&E cistern overflowing?

Nope, its not over flowing but the level is quite near the overflow point but it appears, by the marks around the tank that its always been at that level.

 

[Softus]

Hm. Nothing very conclusive yet then.

Can you identify the lowest radiator in the system, and drain some water from it?

The way to do this is to shut both rad valves open the vent (on that rad), and then gently open the joint between valve and rad, having collected around various paint trays, bowls, a bucket, old towels, and a wet vac.

Drain the rad, and if much of it comes out like Texas Tea then you know you have corrosion.

To reinstate, tighten the joint and open the valves - the system will automagically top up, and you just need to close the vent when water comes out.

 

[2ellett]

This I can do. When I replaced the radiators last year I put two very convenient drain points at the lowest radiators.

Thank you and stay tuned.

 

[2ellett]

I've drained some water as suggested and while I wouldn't say it was exactly Evian it certainly wasn't black more a tad cloudy.

I've heard somewhere about fitting an air seperator between the vent pipe and cold feed to the expansion tank does this mean anything to anyone?

 

[Softus]

I've heard somewhere about fitting an air seperator between the vent pipe and cold feed to the expansion tank does this mean anything to anyone?

Yes - it's simple device that encourages water bound gases to head off up the vent pipe.

Could you remind me where the water is emerging - the water you said was ending back in the F&E?

 

[2ellett]

Sorry for the delay.....

What appears to be happening is that the F&E tank seems to be acting a bit like a radiator and warming up when the heating system is running, hot water being pumped through the vent pipe and back into the tank.

I am, however, in a couple of weeks, planning a clean and flush campaign and refill (plus inhibitor).

 

[Softus]

I am, however, in a couple of weeks, planning a clean and flush campaign and refill (plus inhibitor).

I shall bate my breath until that's done.

 

[2ellett]

Thanks for all of your help Softus. Most helpful.