Radiator Valve Threads

[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