BSP sized lockshield

[alangla]

I think I’m going crazy. Unblocked a section of my heating system at the weekend, but when I was checking the rogue radiator the lockshield was seized. Attempting to free it off resulted in the brass tab on the top snapping off. Fine thinks I, I’ll replace it, I’m sure I’ve done it before. So far I’ve tried 3 different lockshields, Drayton 15mm, Flomasta 10mm and Made4Trade 10mm, none fit. The pipe connection seems to be an old style speedfit type elbow with a captive nut on it, but the nut is too big to fit the 10mm valves and too small for the 15. That tends to suggest it’s a 12mm or 1/2 inch, measuring the bust valve with a ruler seems to confirm this. I can’t find imperial size lockshields anywhere though! System is only about 25 years old, so surely the parts should be available. What am I doing wrong?

[richhead]

alangla said:

I think I m going crazy. Unblocked a section of my heating system at the weekend, but when I was checking the rogue radiator the lockshield was seized. Attempting to free it off resulted in the brass tab on the top snapping off. Fine thinks I, I ll replace it, I m sure I ve done it before. So far I ve tried 3 different lockshields, Drayton 15mm, Flomasta 10mm and Made4Trade 10mm, none fit. The pipe connection seems to be an old style speedfit type elbow with a captive nut on it, but the nut is too big to fit the 10mm valves and too small for the 15. That tends to suggest it s a 12mm or 1/2 inch, measuring the bust valve with a ruler seems to confirm this. I can t find imperial size lockshields anywhere though! System is only about 25 years old, so surely the parts should be available. What am I doing wrong?

Im sure ive got 1/2 inch lockshields from screwfix before.

[.:ian:.]

Probably easier to just replace the bit that goes into the radiator as well, then it will fit. Though it may also be longer or shorter so hopefully theres slack in the pipe too

[ARH]

Show us some pics of what's is not fitting. 1/2 inch pipe is 15mm pipe, or certainly close enough to make no difference, 1/2 inch is the bore size 15mm is the external size. At least as far as I know i could be wrong.

[alangla]

I honestly can’t find them! Looked through Screwfix, Toolstation and spent about 15 minutes knelt on the floor of the local B&Q last night (should probably have tried a church, might have been more successful). The big problem is that the search function on the various apps finds the BSP outlet, but it’s the pipe connection I need in an imperial size.
I found 1 item in City Plumbing that looks to be imperial at both ends, but surely there must be more than that out there.

[alangla]

ARH said:

Show us some pics of what's is not fitting. 1/2 inch pipe is 15mm pipe, or certainly close enough to make no difference, 1/2 inch is the bore size 15mm is the external size. At least as far as I know i could be wrong.

System has been refilled with the broken lockshield back in place to get the hot water running so I can’t photo it dismantled, but I’ll post some pics of what I have in a couple of hours.

[ARH]

Its a bit confusing as the bit that screws into the radiator is a 1/2 inch thread, and the bit the feed pipe goes into is 15mm or 10mm if small bore pipework. Imperial pipework and threads are classified by the bore size, so a 1/2 inch thread is nearly 3/4 inch diameter or so. Pipe is now measured by outside diameter, Don't even think about BSP, BSPT, NPT or any one of the other specs. It's all very confusing.

As far as I am aware the tails on rads have not changed for as long as I have known. It must be nearly 50 years ago I first helped my Dad fit a rad.

Disclaimer, I am not a plumber, but I have done plenty of plumbing at home and whilst developing various machines.

[.:ian:.]

When I added TRVs to all the rads I had to replace the tails on that side as the threaded nuts on the old (1990s) tails were too large for the valves I bought.

[alangla]

Sorry, didn’t get a chance to take the photos last night
this is what I’m trying to replace.


This is too big




These are too small.

The tail on the Drayton one doesn’t fit the existing radiator tail, but I can change that easily enough (if it’s not totally seized), it’s the connection at the bottom of the valve to the nut on the end of the pipe that’s the problem, it seems slightly too big for the 10mm valves and only hangs on if it’s cross threaded, which obviously will blow off as soon as there’s any pressure in the pipework.

I know I’m doing something obviously stupid, but I’m not sure what.

[_Jonesy_]

Presumably the pipe is 10mm microbore - could you just cut the old orange connector off and fit a new Speedfit elbow and a little section of 10mm pipe so it fits in the valves you've bought?

[alangla]

_Jonesy_ said:

Presumably the pipe is 10mm microbore - could you just cut the old orange connector off and fit a new Speedfit elbow and a little section of 10mm pipe so it fits in the valves you've bought?

That’s the conclusion I’ve pretty much come to. Does this look like the right component? https://www.amazon.co.uk/John-Guest-Speedfit-Bent-...

[JoshSm]

Wild guess looking at what's on sale - it was supplied as a single unit so the joining nut isn't quite standard as it's effectively internal to the part?

Buy a new lockshield with a pushfit elbow on it, all the usual names seem to have them in their range. Often a bit nicer looking too as the elbow is also chrome.


First link I found, other suppliers have similar. https://www.cityplumbing.co.uk/p/pegler-yorkshire-...

[alangla]

JoshSm said:

Wild guess looking at what's on sale - it was supplied as a single unit so the joining nut isn't quite standard as it's effectively internal to the part?

Buy a new lockshield with a pushfit elbow on it, all the usual names seem to have them in their range. Often a bit nicer looking too as the elbow is also chrome.


First link I found, other suppliers have similar. https://www.cityplumbing.co.uk/p/pegler-yorkshire-...

That looks like a decent solution. That would fit onto the same 10mm pipe that the speedfit is currently attached to?

[neth27]

Easier to just buy the push fit elbow
https://www.cityplumbing.co.uk/p/drayton-trv4-push...
I used them on mine

Edited by neth27 on Wednesday 5th August 12:23

[alangla]

Does the Speedfit pipe just click into that elbow, then you fit the securing nut, olive and lockshield on top?

Apologies for the obvious naivety, previous valve replacements have just involved undoing the captive nut and tail connection and replacing the body, then re-doing the connection on both sides.

[neth27]

Yes, but don’t forget to put an insert into the pipe.

[neth27]

This is the same layout but with the 15mm elbow

[alangla]

Just want to update this thread and say thanks to everyone for their help, I’ve finally had some time to work on this and I think I’ve got it working, radiator is finally hot after various attempts at clearing both the flow and now the return.

Taking the advice of the posters above I bought this 10mm Flomasta push-fit elbow https://www.screwfix.com/p/flomasta-plastic-push-f...
And mated it to the 10mm Flomasta lockshield pictured above, using the olive supplied with the lockshield. This seems to have got it going and (so far) seems to be watertight. The takeaway from this is that the “captive nut” actually appears to just be the compression nut held in by the compressed olive. If I was doing this again I’d just throw the elbow away and fit a push-fit elbow and 10mm compression lockshield.

Thanks so much everyone, very much appreciated!