Radiator valves - PTFE or not

Jaycee

Is there a washer or "O" ring inside the tail nut?

Haych

Veganic said:

No PTFE required.

 Look at it from the water's view. If you leak past the tapered face what path do you take? It won't be down the thread, it will be straight out of the end of the nut. 

Does that make sense?

Yep that made sense before I asked but I just wanted some kind of confirmation that I wasn’t missing something blindingly obvious, cos that’s what I usually do lol. 

Jaycee said:

Is there a washer or "O" ring inside the tail nut?

Nope, all I have is what you see in the pic ^ 

I’ve been trying to find a technical drawing but nothing out there for this particular valve. Other valves seem to use the same kind of setup but even in the drawings for those it’s not clear how the seal is formed. 

Haych

This is more like what I would expect, a corresponding shape in the end of the tail to fit the valve and a seal on the end to boot:

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F192612713991

hywelg

Emp_Fab said:

How does that even seal ?  I've never heard of a cup & cone plumbing joint, though obviously I gladly bow to your superior knowledge if you're a plumby type.  Every bone in my body is screaming "that will never make a watertight joint".  I can't wait for the response from the supplier...

Excuse the cockiness but I'm still going to say that joint can't be watertight without something else going in there, and even then I have my doubts.

What do you think a compression coupling is then? Exactly the same method of sealing, though not to such tight tolerances as a machined joint as shown in the pic. 

Haych

hywelg said:

Emp_Fab said:

How does that even seal ?  I've never heard of a cup & cone plumbing joint, though obviously I gladly bow to your superior knowledge if you're a plumby type.  Every bone in my body is screaming "that will never make a watertight joint".  I can't wait for the response from the supplier...

Excuse the cockiness but I'm still going to say that joint can't be watertight without something else going in there, and even then I have my doubts.

What do you think a compression coupling is then? Exactly the same method of sealing, though not to such tight tolerances as a machined joint as shown in the pic. 

A normal compression joint relies on the deformation of the copper olive and the copper pipe to make the seal. 

Neither of these parts are soft enough to deform under pressure, though. I could very well be wrong but even if they are machined to a tight tolerance, after chrome plating them is that tolerance preserved. Even machined parts usually require a gasket of some kind. 

Like I say, though, I could be wrong. 

hywelg

Haych said:

A normal compression joint relies on the deformation of the copper olive and the copper pipe to make the seal. 

Neither of these parts are soft enough to deform under pressure, though. I could very well be wrong but even if they are machined to a tight tolerance, after chrome plating them is that tolerance preserved. Even machined parts usually require a gasket of some kind. 

Like I say, though, I could be wrong. 

You are. The compression of the olive ONLY serves to seal the olive to the pipe. The joint itself is sealed by contact of both ends of the olives' conical face with the cup of the body and of the nut. Hence why you can undo the joint and redo it many times. Exactly the same sealing mechanism as in that valve, though there are two mating faces in a compression coupling. 

Perdix

Traditionally the cup and cone radiator valves would have had brass faces that are soft enough to make a seal. Most modern plated ones will have a rubber o ring on the face of the cone. Not all do and I have fitted plenty with just jointing paste to take up any discrepancies in the manufacturing process 

Haych

hywelg said:

Haych said:

A normal compression joint relies on the deformation of the copper olive and the copper pipe to make the seal. 

Neither of these parts are soft enough to deform under pressure, though. I could very well be wrong but even if they are machined to a tight tolerance, after chrome plating them is that tolerance preserved. Even machined parts usually require a gasket of some kind. 

Like I say, though, I could be wrong. 

You are. The compression of the olive ONLY serves to seal the olive to the pipe. The joint itself is sealed by contact of both ends of the olives' conical face with the cup of the body and of the nut. Hence why you can undo the joint and redo it many times. Exactly the same sealing mechanism as in that valve, though there are two mating faces in a compression coupling. 

Sorry but I don’t follow your logic. A compression joint still relies on the deformation of the olive at the very least - it’s a softer material than the brass cones and thus conforms under pressure to the surface of the pipe and the mating surfaces of the cones to create a water tight seal. 

Where you have two very hard surfaces you almost always need a third softer gasket material to do the same job - to deform and conform to the surfaces of the parts you want to join together to create a seal. 

High machined tolerances are one thing but as I said before after chrome plating those tolerances won’t be preserved even if they existed to start with. I’m not sure such high tolerances are achievable for £20 a set of valves.  

Veganic

The 'hard' plating will be over a softer material.

Just stop procrastinating and show us a picture of the installed valve. Or a video if it leaks

Haych

Veganic said:

The 'hard' plating will be over a softer material.

Just stop procrastinating and show us a picture of the installed valve. Or a video if it leaks

It's not a soft material though, I don't know what it's made out of but I tried to nut them up last night and even with a great big spanner and as much might as I could muster I didn't make a scratch in the plating let alone deform anything to make any kind of seal.

Emp_Fab

I reckon there's a rubber / neoprene washer that goes between them.  

Haych

Well, would you Adam and Eve it, they seem to work. 

I decided to rig one of the valves up to the outside tap this evening and blanked off the other end after the tail. 

Turned the water on, opened the valve and not so much as a weep. 

I dont understand it at all but it does work! I have properly been stood corrected. 

So at mains pressure it seems sound. I guess I’ll have to stop doubting and trust that whoever designed the fitting knew what they were doing. 

My apologies to @hywelg for being a pedantic so-and-so in the process, I still don’t get it, it goes against all engineering principles I’ve ever known but work it does!

hywelg

Haych said:

Veganic said:

The 'hard' plating will be over a softer material.

Just stop procrastinating and show us a picture of the installed valve. Or a video if it leaks

It's not a soft material though, I don't know what it's made out of but I tried to nut them up last night and even with a great big spanner and as much might as I could muster I didn't make a scratch in the plating let alone deform anything to make any kind of seal.

They are plated brass. 

Emp_Fab

Haych said:

Well, would you Adam and Eve it, they seem to work. 

I decided to rig one of the valves up to the outside tap this evening and blanked off the other end after the tail. 

Turned the water on, opened the valve and not so much as a weep. 

I dont understand it at all but it does work! I have properly been stood corrected. 

So at mains pressure it seems sound. I guess I’ll have to stop doubting and trust that whoever designed the fitting knew what they were doing. 

My apologies to @hywelg for being a pedantic so-and-so in the process, I still don’t get it, it goes against all engineering principles I’ve ever known but work it does!

Well colour me danglewhacked in the jimmycrackers.  I would have put good money on that not sealing.

You learn something new everyday.