On Mon, 05 Jun 2006 05:10:03 -0700, tonyjeffs wrote:

I bought a B&Q towel rad, and a pair of valves.
I thought the valve threads would be taper fit, but they're not; they
don't tighten to seal.
I managed to seal the non-tap side with ptfe, but the tap-valve has too
short a thread.

What do you mean by tap-valve?

Your radiator may have screw-in plugs at the top, one or both with air
bleed valves (or maybe one is blank) and these should have rubber rings to
seal them. Fernox LS-X or silicone bathroom sealant would do if the rings
are missing.

The radiator valves tails seal into the radiator with PTFE wrapped around
them (or silicone/LSX). The joints between rad valves and pipe are
compression requiring a copper or brass olive and require no sealant.