radiator auto bleed valves

They get blocked after a time. The constant wetting & drying will precipitate crud/scale inside them. I think the problem is common to virtually all auto bleed valves.

I have one of those above my boiler. It failed causing water to weep down into my boiler causing a lot of damage. I believe that they?re only really recommended for use when refilling and degassing a system for a few days.

I have a ball valve fitted below it now so that once degassed, I can shut it off completely.

Tim

There are two sorts. One has a float. The other has a material which shrinks when it dries out (usually a washer) and swells when wet. You have to soak them in water (or let them be soaked) before they close off. Haven't seen the latter for years though.

I can get to the locking caps on mine. When filling I loosen the cap and let it auto-vent for a few days. I then screw down the cap which will prevent water leakage if it fails. As mentioned previously I don't get an ongoing problem with air after a few days after refilling etc.

The Aladdin ones fitted to radiators are effectively the latter type. I wouldn't expect them to work too well if the system were drained down and then refilled soon afterwards as they wouldn't have had time to dry out. In my case the radiators had been removed and drained down for a few weeks allowing time for the valves to dry.

Bleeding radiators is hardly rocket science. I would rather be in control of it than trust an automatic valve.