boiler flue

[<me9]

The flue on my 15 year old glowworm complheat boiler (Concentric fan flue) is corroding, due to condensation in about the outer two thirds of its length. The corrosion was blocking about 25% of the flue area, and causing staining on the wall below the flue.

The flue is installed absolutely horizontal, resulting in the condensation sitting in the pipe. It is *not* a condensing boiler. Return temperature (apart from in initial warm up) is high enough to prevent condensation in the boiler.

Would it be worth adjusting the eight of the hole in the wall, to permit the flue to drain? If so, into or away from the boiler. I suspect the latter would be preferable to the current situation, but wonder if it would increase tha staining. The outlet is in a fairly sheltered (from rain) alleyway, so the staining doesn't get washed away, and is only removable with acid.

[John Stumbles]

Non-condensing boiler flues generally should slope so any condensate runs away from the boiler (condensing boilers vice versa). However if the flue has corroded through it must be replaced, and the integrity of the flue must be assured whatever you do.

[<me9]

I'll see how easy it is to lower the hole in the wall slightly.

I had enough spare flue from the original installation to replace as it used just less than half of a 3 metre kit. However, on close inspection and cleaning the flue is intact, and not as bad as first thought, so I'll leave it.

Is it worth putting a spot of alumslip on the fan spigot into the flue, it was very hard to undo, but succumbed to a bit of heat.