Radiator valves - PTFE or not

Haych

I've done this before so I should know but all common sense has escaped me today...... and it's been a while.

I'm installing a new radiator in my daughter's bedroom and I have new valves, too. I've used PTFE tape on the valve tails into the boss on each side of the rad, but do I need to use PTFE tape on the joint between the valve tails and the valve itself?

I'm also confused about the joint between the tail and the valve, there doesn't seem to me much to create a water tight seal - am I meant to use any kind of sealing compound in this joint too?

https://imgur.com/gallery/Gqsr0q1

Thanks in advance

iseverynamegone

No you don’t, just the tails. 

Haych

iseverynamegone said:

No you don’t, just the tails. 

Thanks, much appreciated.

So what makes the seal between the tail and the valve body then?  

boogieman

Haych said:

iseverynamegone said:

No you don’t, just the tails. 

Thanks, much appreciated.

So what makes the seal between the tail and the valve body then?  

It’s two flat, machined surfaces. Doesn’t need any sealant. 

I’d use PTFE on all the threaded joints, just as belt and braces. 

Haych

boogieman said:

It’s two flat, machined surfaces. Doesn’t need any sealant. 

I’d use PTFE on all the threaded joints, just as belt and braces. 

They're not flat, though.  One is convex, the other concave.  Unless one is made of a softer metal that's supposed to deform to create the seal under compression I'm not understanding and that both parts are chrome plated (i.e. hard) doesn't give me confidence it's not gonna leak to be honest.

Maybe I'm over thinking it and should just get on with it.  I just wish I could remember what I did last time, I'm looking at that rad now and it's never leaked!

Emp_Fab

Those are compression joints.  You use an 'olive' on the pipe that sits between the nut and the valve.  The soft copper olive deforms to create the seal.  https://en.wikipedia.org/wiki/Compression_fitting

Use ptfe tape on threads only.

I'm assuming that thing on the right hand of your photo is an air bleed valve for the radiator ?  I can't quite work out what it is !

Haych

Emp_Fab said:

Those are compression joints.  You use an 'olive' on the pipe that sits between the nut and the valve.  The soft copper olive deforms to create the seal.  https://en.wikipedia.org/wiki/Compression_fitting

Use ptfe tape on threads only.

I'm assuming that thing on the right hand of your photo is an air bleed valve for the radiator ?  I can't quite work out what it is !

There is no olive, this is the joint between the tail and the valve body - that thing on the right is the valve tail.

Emp_Fab

Aaaah !   I've just got it.  That thing on the right is the radiator tail, but the nut is upside-down !

Wow... I've never seen one like that before !  Just a convex and concave surface to seal ?

Haych

Emp_Fab said:

Aaaah !   I've just got it.  That thing on the right is the radiator tail, but the nut is upside-down !

Wow... I've never seen one like that before !  Just a convex and concave surface to seal ?

Yes, sorry the nut is upside down.  That's about the size of it, though, bud.

Emp_Fab

I've got no idea.  That is the strangest thing I've ever seen.  I can't imagine it sealing at all with just the mating surfaces.  The chrome plating will see to that for starters.  Did the tails come with the valves ?  Do you have a make / model / description of some sort that you can google for instructions or other folk in the same situtation ?

Emp_Fab

You know.... I don't think they're meant to fit together.  The internal bevel on the valve looks like a straight angle and the tail is obviously a convex curve.  The contact area between those two is going to be miniscule.

Emp_Fab

Hang on.... that "tail" is hollow isn't it ?  It's not just a posh blanking plug is it ?

Haych

Yeah the tails did come with the valves - they are called Milano and came from bestheating.com - I'm sure I've used them before but can't recall how they went together even though it was only a couple of years ago.

Haych

Emp_Fab said:

Hang on.... that "tail" is hollow isn't it ?  It's not just a posh blanking plug is it ?

Yes, it's hollow, if you mean it's to allow water in and out of the rad.

Emp_Fab

Well, I've Googled the shit out of that and come up empty.  Were the tails in the same box as the valves ? (i.e. how certain are you that they are meant to fit together and Bestheating haven't just lobbed in a couple of tails from some weird towel rail or something ?

All I can suggest is that you ring them in the morning mate.  I'd love to know the answer though !!  I'm 90% sure that those two bits are not meant to be together though.

boogieman

Haych said:

boogieman said:

It’s two flat, machined surfaces. Doesn’t need any sealant. 

I’d use PTFE on all the threaded joints, just as belt and braces. 

They're not flat, though.  One is convex, the other concave.  Unless one is made of a softer metal that's supposed to deform to create the seal under compression I'm not understanding and that both parts are chrome plated (i.e. hard) doesn't give me confidence it's not gonna leak to be honest.

Maybe I'm over thinking it and should just get on with it.  I just wish I could remember what I did last time, I'm looking at that rad now and it's never leaked!

Ah, sorry I hadn’t seen the photo link. They’re normally a flat surfaced joint and don’t have any sealant or washers. I presume the convex and concave bits just mate up and doing the nut up tight is enough to give you a watertight join. I still reckon you won’t need any sealant in there, but you should still put ptfe tape round the threaded part. 

Haych

Emp_Fab said:

Well, I've Googled the shit out of that and come up empty.  Were the tails in the same box as the valves ? (i.e. how certain are you that they are meant to fit together and Bestheating haven't just lobbed in a couple of tails from some weird towel rail or something ?

All I can suggest is that you ring them in the morning mate.  I'd love to know the answer though !!  I'm 90% sure that those two bits are not meant to be together though.

Yes the tails were in the same box, pretty sure they are meant to go together as I have two pairs since the first pair they sent out had damaged heads - tails are identical in both.

Just tried to fit one valve and tail together with a spanner.  I put as much grunt behind the joint as I could but when I took it apart again there isn't so much as a scratch in the chrome plating on either part!

I've sent them an email, hopefully they'll either confirm a missing fibre washer or something or will confirm they are as they should be.  Watch this space.

Veganic

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?

hywelg

You need ptfe on the threads that go into the radiator,  which will be BSP(T), tapered . You'll need an Allen key and an adjustable spanner on the end of it. Then the cup and cone joint from the tail to the valve body dies not need ptfe. Likewise the compression joint to the pipework. 

Emp_Fab

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.

@veganic I'm not getting you....   if you have water in the radiator, under pressure, it's going to go through the centre hole in the tail piece, and encounter resistance at the valve.  Where's it going to go ? - it's going to weep out of the non-watertight joint between the convex surface of the tail and the bevelled surface on the valve.... onto the floor.  Could you clarify what you're saying ?

Perdix

No PTFE on the concave/convex face or on the threads around the concave face. The two faces  are supposed to be machined to a sufficient tolerance to not require any additional help making a watertight joint. However from experience a small smear of jointing paste on either face will help make a satisfactory joint.