Bleeding radiator too often

[rudenotto]

Hey folks, I did quick search, couldn't find anything to quickly answer this, so hope some nice plumber can assist. I work in Financial Services

I have to bleed the upstairs bathroom towel rail often, prob once per month as the top half is cool when the lower half is hot. All other rads in house are fine, upstairs and down. It's only the towel rail. The hot water tank is also in the bathroom. It's a grundfos pump. Gravity fed, cold water tank in loft.

Any reason why only this radiator lets air in? Any quick solution? Thanks.

 

[RigidRaider]

It doesn't let air in, water would be leaking out if it had a leak. The insides of your steel radiators are probably oxidising and hydrogen gas is forming. Hold a light to the bleed valve next time you bleed and a small flame will confirm, see: http://www.youtube.com/watch?v=zMjYnTGV9ks

Try increasing the dosage of Fernox, an antioxidant, in the system. Give it a few weeks to settle down.

(Possibly the system is pulling in air at the top in the F&E tank but I would go for the hydrogen option first)

That's £100 for the advice, please.