Dumb question of the year - how long is a bleed screw

[Martino]

Mother-in-law has a problem which I entered on another post.
While I was looking at her pipework (the house, not her personally) I noticed one of the radiators is a double panel one where the front panel gets nicely hot but the rear panel stays cold. Each panel has its own bleeds screw. Front one bleeds OK - no air, just water. I tried to bleed the rear one but seemed to be turning the bleed screw a helluva long way and getting nothing out - neither air nor water. It's not the end of the world - the radiator is in a spare bedroom and gets plenty hot enough anyway. But it got me wondering - how long is the thread on an average bleedscrew - how far can I turn it before it pops out? Well, I did warn you in teh subject that it was a dumb question.

 

[numpty1]

isolate radiator,remove bleed screw,poke thin wire into orifice,listen for air ,replace screw ,open valves and test operation.
different rads have different size vents most are about 5/10mm long.

 

[seco services]

there useally only a few mm long the thread.

you may find its blocked with a bit of crud.
if you shut both rad valves and hold a container under the bleed valve then you can remove it and clean it.