Bleeding cast iron radiators

[No.Sp]

Hi,

I've just fitted a couple of cast iron radiators, picture of which can be seen here -

warm up OK but only the bottom half of the radiators. I'm guessing there's air at the top which is causing the problem. However, the only valve fitted is a few inches above the outlet (you can see it sticking out on the picture). There's no valve at the top of the radiator.

Is this normal? Is hot air gathering at the top causing them not to heat up? If I open the valve, then water just comes out.

Cheers,

Steve.

[RW]

IANAP......But.....Perhaps you lay the rad on its side and fill with the bleed hole open to expel air then mount upright

[Tim Downie]

Very weird. Never seen a radiator, cast iron or otherwise without a bleed valve at the top. Are you quite sure that there isn't a recessed square screw (perhaps buried in layers of paint) at one end of the radiator?

If not, I would suggest that your best bet is to contact the sellers and ask them how you're supposed to bleed them. Without a bleed screw, they're not fit for purpose.

Tim

[No.Sp]

Well, there is a notch which looks like it's there to take a flat bladed screwdriver (you can see it at the top in the centre of the circular piece). It has one on each end. It might be for the tie rid, that said there's a seperate tie rod underneath.

I bought them secondhand a few years ago, so no comeback I'm afraid.

How does the water flow through these? Is it a common feed at the bottom? Or does it flow up and down the first section which then feeds the next one?

Steve.

[Andrew Gabriel]

Not sure if you're saying they only have one connection? If so, they were steam radiators, which also explains why no bleed valve. (There was an automatic vent to let air out each time the steam system started up, like you get on a pressure cooker, which could be what that low down valve was originally for.)

[Bob Minchin]

Not too difficult to drill and tap for a bleed nipple. Some are threaded 1/8 BSPT (which is about 3/8" od). This thread is quite fine (28 tpi) and will give a decent few turns into relatively thin materials.

Bob

[Bob Martin]

My house still has cast-iron radiators, probably installed around 1940. They are connected as 5 vertical pairs (ie from the loft to the bedroom rad then down to a downstairs rad then back to the boiler). Only the downstairs one of each pair has a bleed screw. I don't know why it works - to me it would make more sense if the upstairs one was the bleedable one - but it does.