lockshield with drain off?

Depends what you've got below or near the lockshield, in cases where there would normally be an elbow, I tend to replace with a tee, and use one of these

Remember that the radiator will be at pressure so you cant prevent it from pissing out some water by just closing the valves and the air vent.

I have these and the screwdriver operated drain seems good - you can have a hose fitted to the drain end.

In article , John writes

I did wonder about that but they suggest you release pressure on any trapped air by opening the bleed vent first and then closing it before opening the drain screw over a drip tray and fitting a hose

Possible faff, but they are dinky.

radiator and pipe will now be different than for anything else on the market? Probably not enough to matter - but it would be a shame to have to move the pipes if I needed to change a broken lockshield down the line. Sometimes pipes won't stretch where you want!

I realise now I have a really stupid question: do people PTFE the connections, or use boss white, or just hope? I'm asking about both the screw thread into the radiator, and the compression-ish fitting between the other end of that and the valve itself.

Cheers, David.

In article , David Robinson writes

The threaded connections into the radiators?

Yes, they need sealed. My first experience of using ptfe tape was on radiator stems and it was a complete disaster, many turns were used but sharp burrs on the quality, brand named rad threads tore the tape and

I happened to use Dow Corning PlumbaThread as it was cheap and easily available from my local RS Trade Counter but loctite and many others are available from the likes of Toolstation, Screwfix et al.

Don't waste too much time worrying about pipe location changes, you can guarantee that whatever scheme you choose will be thwarted by some incompatibility/obsolescence in the future.

A large radiator will need to squirt out quite a bit before its pressure is released.

I've got Matchmate drain-offs - as per your first reference - on virtually all my rads, and they are brilliant.

They're very easy to install because the connections are dimensionally identical to most ordinary 90 degree lockshields - so it's a straight swap with no pipework changes. You need a bit of space at the end of the rad, of course, in order to operate the drain. [I was unable to use one on one of my rads because it's too close to the corner of the room].

They're also easy to use when you want to drain the rad. There's a sequence of steps which you need to follow, but it's very straightforward - and I certainly wouldn't regard it as a faff.

I proceed as follows:

1. Turn off both valves, making a note of how many turns are required to shut the lockshield
2. Crack open the bleed screw to relieve the pressure (not usually needed on a vented system) and close it again
3. Remove the plug from the drainpipe [1], having put an old towel underneath to catch any drips - but virtually nothing comes out
4. Put a container[2] under the drain pipe to catch the outflow, and open the bleed screw just a little in order to get a steady, controllable, stream

Doubtless some clot will be along in a minute to tell you that you don't need any of this - but simply need to carry the full radiator outside with your thumbs over the ends of the tails. All I can say is that I'd rather do that over *his* carpets than *mine*!

I avoided those because the pipework would have to be moved to accommodate the extra rad to valve spacing - whereas the Matchmates were a straight swap.

For screwing the tails into the rad, I use gas-grade PTFE tape which is much tougher than the standard stuff and tears less easily.

For good measure, I clean up the threads with a 1/2" BSP tap[1] before fitting the tail

The compression joints *shouldn't* need sealing - and *don't* wrap PTFE tape round them - but I always smear a bit of LS-X round the olive for belt and braces

That's fine for draining the pipework, but not so useful for keeping the pipes full and draining individual rads - which is what I think the OP wants to do.

In article , John writes

How so? Water is incompressible and so cannot retain any pressure. Pressure can only be retained by any unbled air in the radiator which can be released via the bleed valve with perhaps a trickle of water.

This is the case when both ends of the rad are turned off as described in the instructions. Any pressure stored in the system (via the expansion vessel could then be released by opening the rad valve to link the system back to the rad.

Perhaps the quantity isn't massive - but the pressure makes it seem a lot. I guess there is some air above the bleed valve - and some elasticity in the construction of the radiator. I have only just gone"pressurised" and it took me by surprise.

I think, "Pressure can only be retained by any unbled air in the radiator which can be released via the bleed valve with perhaps a trickle of water." covered that.

Trickle is more like an aerosol jet.

In article , John writes

I think you must have paid extra for those full flow bleed valves ;-). Never more than a hiss, bubble, bubble here, never felt the need to open the screw enough to have it hosing down the walls.