Radiator Valve Threads

[acsmith1986]

Hi oz-plumber it's not a safe bet! I have tried a 3/4" cap also and that doesn't fit.

 

[fixitflav]

But if it is indeed 1/2" I can buy new tails for the rads with 1/2" BSP connections which will fit a new TRV with a 15mm to 1/2" connection?

Yes, but it doesn't have to be a TRV. For the cost of an iso valve you could use one of them while you're doing the work. Probably use it somewhere anyway.
To answer your points about thread types - modern 15mm compression fittings use 1/2"BSP threads, but I have some old ones with finer thread. Obviously if you have both parts it doesn't matter. I also have 22mm compression fittings with different threads. Neither is 3/4"BSP as there is insufficient wall thickness for a 3/4"BSP thread when 22mm is subtracted from the OD of a 3/4"NB pipe.

will give getting the tails out a go at the weekend and see how it goes, fingers crossed!

They could be tight! Might be sealed with hemp and Bosswhite, which goes hard. Be prepared to warm it up with a blowtorch to soften it. If you give it too much welly you might rip a piece out of the rad.

 

[Best]

That is an old Peglers Terrier rad valve and if the thread is very fine, then it is the older type thread Peglers used, of 1970s era.
You can’t be experienced in plumbing if you can’t plug the radiator or the valve?
Just push the nut and olive from the old tail by using an adjustable spanner with a twist behind the nut. Then you can fit a brass stopend on old tail, if you really must.
Or the old nut can be used with a new olive and a cutting of copper that has a stopend on other end, to provide a seal off pipe.

 

[bazzlar]

That is an old Peglers Terrier rad valve and if the thread is very fine, then it is the older type thread Peglers used, of 1970s era.
You can’t be experienced in plumbing if you can’t plug the radiator or the valve?
Just push the nut and olive from the old tail by using an adjustable spanner with a twist behind the nut. Then you can fit a brass stopend on old tail, if you really must.
Or the old nut can be used with a new olive and a cutting of copper that has a stopend on other end, to provide a seal off pipe.

Old pegler valves use bspf threads not standard BSP as do all valves now.

 

[fixitflav]

Old pegler valves use bspf threads not standard BSP as do all valves now.

That's interesting. I've not heard of coarse and fine BSP threads. Can you give more detail? I looked on Google which didn't say anything. As I said in #17, for eg 22mm, compression fittings aren't 3/4BSP, and the modern coarser thread is finer than 3/4BSP.

 

[fixitflav]

That's interesting. I've not heard of coarse and fine BSP threads. Can you give more detail? I looked on Google which didn't say anything. As I said in #17, for eg 22mm, compression fittings aren't 3/4BSP, and the modern coarser thread is finer than 3/4BSP.

This has gone a bit quiet.
All my rad iso valves are old, about 30 years, and the the valve tails are 1/2BSP (of course), and the tail has an internal 13mm drive hexagon. The valve has 15mm (or maybe 1/2") compression on the pipework side.
The valve rad side has a male thread, with same OD as 3/4BSP, but finer thread. A 3/4BSPF fitting goes on about 1 turn. Estimated 19 TPI (same as 3/8BSP), vs 14 TPI for 3/4BSP. Anybody know what thread this is? I've never heard of a fine series BSP, and I can't find anything on the internet.
My TRVs, and I believe modern iso valves, have 15mm compression both sides, and the rad tail has external spanner flats.

 

[Best]

This has gone a bit quiet.
All my rad iso valves are old, about 30 years, and the the valve tails are 1/2BSP (of course), and the tail has an internal 13mm drive hexagon. The valve has 15mm (or maybe 1/2") compression on the pipework side.
The valve rad side has a male thread, with same OD as 3/4BSP, but finer thread. A 3/4BSPF fitting goes on about 1 turn. Estimated 19 TPI (same as 3/8BSP), vs 14 TPI for 3/4BSP. Anybody know what thread this is? I've never heard of a fine series BSP, and I can't find anything on the internet.
My TRVs, and I believe modern iso valves, have 15mm compression both sides, and the rad tail has external spanner flats.

Are you talking about the old large nut tails which have tapered flange on tail and valve? You can still get quality valves like that, but Trvs are now rare with that tail.
Why worry about them? Just remove the tails and install the new valves and tails

 

[fixitflav]

Are you talking about the old large nut tails which have tapered flange on tail and valve?

Probably, if what you mean has same diameter (but not TPI) as a 3/4BSP.

You can still get quality valves like that, but Trvs are now rare with that tail.

Interesting that they're still available and considered good quality. As I said, my TRVs are 15mm compression both sides.

Why worry about them? Just remove the tails and install the new valves and tails

I'm not tackling a job at present, just curious. But thinking about it a bit more, I don't know what the thread is on 15 compression (earlier ones which aren't 1/2BSP), or 22mm compression (at least 2 different TPIs, neither 3/4BSP). I'd have expected makers to use a standard thread of some sort, but maybe not, and they do a special. Obviously as you have both parts it doesn't matter.

 

[sammathias]

Will be same threads as Honeywell zone valves or kuterlite compression fittings being BSP parallel threads.

 

[fixitflav]

Will be same threads as Honeywell zone valves or kuterlite compression fittings being BSP parallel threads.

15mm compression fittings usually have 1/2" BSP parallel threads, but 22mm do not have 3/4" BSP. Please read earlier posts.

 

[sammathias]

Oh I must be completely clueless, please forgive my stupidity.

 

[quality]

most imported compression fittings are standard BSP kuterlite is not also zone vale manufacturers have for many years bastardised their threads for some reason, maybe their supplier. I have not read all the posts but 15mm has been 1/2" bsp 14 TPI for over 40 years but there is some stuff out there older. We do refrigeration work also and come across all sizes of pipe thread, BSP, BSPT, NPT and on the odd occasion APT they are not that much different but they are different