One reluctant rad

Further to recent posts.... completed drain down/flush. Changed a couple of leaky rad valve, re-filled, re-started. No major problems - this time no banging from the boiler (did a slow re-fill and was very careful with bleeding). However, one rad is still reluctant to heat up and I wonder whether this could be the problem.
We had our central heating piping re-routed - previously had feeds dropping down from a bedroom (yes the same one with the cool rad) - the feeds were cut off and capped. The capped pipes are approx 24 inches in length off the t's. Could these capped pipes be causing an airlock problem on the return of this cool rad, preventing proper flow of water?

P.S. IS the pump bled by undoing the central pump screw and when the air comes out does it make an interesting noise?

Are the capped off pipes orientated vertically above or bellow the main pipe runs

Try closing all the other rads except the one that in cold, that sometimes gets the water flowing through it.

(moving water has a lower pressure than static water, of lot of tradesmen refer to water as being lazy, perhaps this is why?)

P.S. IS the pump bled by undoing the central pump screw

Click to expand...

yes

and when the air comes out does it make an interesting noise?

Click to expand...

Phht (very quick!)

Tks Brumylad.

Capped pipes are in the same plane as main pipe runs or so I suppose they are level, but I know they are unsupported. Not sure if this answers your question?

any air trapped in there is gona expand and cause flow problems, I've heard of dead legs causing this kind of problem before.

You could replace the ends with manual air vents, I know its not good to have these under the floor, but hell plenty of pumps installed under floors.

The other option is to remove the T's. You can obtain slip couplings if the pipe work is very tight.

Thanks for the advice - carpets up and replace the t's then.

Cheers

if your stop ends are compression you could try loosening them slightly