Three rads not heating - all seem to have water

L1011

I had one radiator replaced (bathroom refurb) a while ago, when it was still warm out. Didn't check the heating at the time other than the hot water working.

Since then, three rads are not heating at all - pipes to them are cold etc. I assume it has to be an airlock, but all three will put out water when bled, as if the water to them is being replenished. One of them puts out a marginally scuttery flow, but its still quite a bit of water. One of the ones that works is constantly getting small amounts of air in it too - I could bleed it five times a day and get air each time.

The rads that aren't working aren't even on the same floor, but might easily all be the ends of the line for that individual floor.

This is a 1990s bodge retrofit to a formerly electrically heated house that is pressurised from a header tank (actually it might even be the single attic water tank...), so there's no valve stopping water getting in to the system, as far as I know. Hot water from the boiler gets to the hot press where there's two motorised valves to control it going to the cylinder and the radiators - no further zoning of rads. Most of the rads are the old type with valves that are very hard to drain water out of, two that are working have the modern type that open with a screwdriver, one of which can be directed to a bucket or something - but that rad is fine.

Is there something obvious I might be missing here? Should I just get a load of towels and keep going at the cold rad that has the slight scutter of air in the water coming out? And where could cold water to refill the rads that have had water come out be coming from - airlock between the hot side and where the cold from the attic comes in?

dbas

https://www.boards.ie/discussion/2058267748/three-rads-not-heating-all-seem-to-have-water

You need a plumber.

System could need balancing and well as flushing if those rads are old

L1011

Trying to find one for a small job around here is near impossible, I'll spend a day chasing one if I have to.

Rads were powerflushed when I changed from oil to gas about five years ago; and rust inhibitor put in at the time; also have some mag filter setup on the return to the boiler so I'd hope they don't need to be flushed again.

Wearb

Turn off all working rads and see if the others heat. If not then turn off all but one and see if that one heats. Keep hotwater zone off.

Tow

Assuming original post is correct. Check you pump is running properly, if so turn it up to turn it up to full power. Ensure motorized valve to rads is open and cylinder is closed. Turn them all off rads except one, see if it clears the air lock. Repeat to each for each rad turning them on one at a time.

L1011

Went to check which valves were on which side on each radiator and found that one of the not working ones was off at its TRV - it was exceptionally inaccessible so I hadn't actually felt the pipes going in to it. It is now heating.

Going to run the system up to heat and try a normal bleeding again now that there isn't one off; if (OK - when, more likely) that does nothing, I can now actually access all the valves to turn them all off and do as suggested above.

L1011

Calling a plumber...

Could hear some air gurgling around the place when doing the one rad at a time thing, but none ever made itself available to bleed at the bleed valves. There's a Caleffii robocal on the hot side of the motorised valves; and there was another on the return side with the plastic valve missing - which I then found on the floor; this may have vented some air out.

But still cold pipes going to the two final radiators