On Sun, 20 Dec 2020 11:15:04 +0000 (GMT), Dave Plowman (News) wrote:

It's odd. My towel rail also needs bleeding from time to time. It's not
the highest rad in the system either - by a long way.

Is it the first inverted "U" from the boiler? Air released from the
water by the heating will collect there. This doesn't have to be the
highest point in the system 'cause air won't travel down wards very
easily.

--
Cheers
Dave.