Getting a plumbing nut back on!

If you unscrew the union from the rad+tail, does it seat any better and allow the bottom nut to do up first?

Anyone know why modern valves seem to be compression with olives on the vertical pipe and horizontal tail, instead of unions, continental influence perhaps?

Ah, there;s an idea :) Will try that, thanks.

NT

I've no idea. Fwiw the new tail etc on the other end is a fair bit smaller than the 30 yr old one that was the other way.

NT

I guess that the pipe was painted after the connection was made in the past.

With the pipe free of the valve does the nut freely slide up to the olive or is it binding on the paint? If so, try some wire wool/emery cloth to get the paint off the pipe just below the olive so the nut slides up without binding and/or use a spanner to hammer up the nut (on both sides of the pipe together) to the olive before offering up the pipe to the valve.

There's your answer. Look at the valve you took off. Old compression fittings often had a non-BSP (or at least finer pitch from standard BSP, I've no idea about the profile) thread. You'll need to get the olive off and use a new nut. BTDT, if you haven't got a proper tool *very* careful use of a hacksaw and splitting the olive with a screw driver rotated in the hacksaw slot when halfway through works.

Well of course I'm wrong if it is the same nut and valve. If there isn't anything like corrosion in the way the olive must have slipped down the pipe somehow. Best take a couple of mm off the end of the pipe, or try a temporary fitting with a deeper pipe recess to pull the olive nearer the end.

Use a junior hacksaw /diagonally/ so that it doesn't touch the copper, go rather more than half-way through, especially with a brass olive, then the screwdriver, as Roger sys.

Have fun getting a leak-free joint.

If you can solder, just chop 3 inches off, and fit a new bit of pipe with a new olive.

remember, olives crimp into the pipe, deforming it, and if a gorilla had made the original joint then the pipe will be damaged beyond repair.

Is the pipe hitting a shoulder inside the fitting?

I think there's a bit too much of the olive showing. Is that what you have in mind too? The pipe's not fully in the fitting?

Assuming as the OP says it is the original pipe, nut and valve then only three things could cause this appearance; an artefact of the photograph being taken without the pipe being fully pushed home, this would be irrelevant to the problem; corrosion products or debris on the pipe seat in the fitting or on the olive seating preventing it fully entering the fitting; or the olive being inadvertently pushed down the pipe, thought I am not sure how, and sticking there due to sludge drying out.

Or, if the radiator has been taken off, it might not have re-seated properly on its bracket, and may be riding high.

Or the pipe has dropped a bit, and the OP hasn't given it a yank upwards.

Thanks to everyone for the ideas. What worked was sanding the paint off. The tails are pulled up as the nut does up. I hadn't changed any parts on that end of the rad, the other end got a new TRV.

NT