Replacing TRVs but Unsure of Current Setup (10mm pipe but 15mm TRVs?)

[Savo]

Hi,

I am looking to replace some TRVs that have stopped working on 4 radiators, however, the setup looks a little unusual. The pipework is 10mm but the TRV looks like it might be 15mm with some sort of reducer going into the TRV from the pipe. The reducer doesn't look like anything I can find on Screwfix/Toolstation and so I am guessing it is either a really old fitting, or I'm just looking for completely the wrong thing! I have attached photos of the TRV and the lockshield. The lockshiled looks to me like it is a 10mm lockshield as the pip is 10mm and it looks like the lockshield has been attached directly, so I think it is just the TRV side that is the unusual setup.

I just want to know what the current setup is and whether the "nut" between the pipe and the TRV is a reducer, and whether I can just re-use that and effectively do a like for like swap of the TRV. If not, then any advice on what fittings I would need would be much appreciated as I am not really sure what I need and want to make sure I have all the right parts before draining the system down.

TRV, possible with reducer

• Savo
• 1 Oct 2020

Lockshield on 10mm pipe

• Savo
• 1 Oct 2020

Thanks,

Ian

 

[muggles]

You won't get anything like that any more. You'll need a 15×10 coupler and a short length of 15mm to go into a new valve. Either that or a 10×10 coupler, a short length of 10mm, and a TRV with a 10mm adapter in it.

 

[Savo]

Hi Andrew,

Thanks for the quick response. So, going by the picture, is there likely to be an olive on the pipe going into the fitting? I'm just a little worried as I've not replaced a TRV before and I know that there is no "play" in the pipes so I can't really cut any length off the pipe to remove an olive (if there is one) and if I use a junior hacksaw to try to get the olive off I'm 99% sure I'll end up damaging the pipework!

You mention a 10x10 coupler, a short peice of 10mm and a TRV with a 10mm adapter. I might be missing something but why would I need the 10 x 10 coupler and short 10mm pipe if I was to fit a 10mm TRV to the existing 10mm pipe (or is this because I'm going to have to cut the 10mm pipe, therefore shortening it?).

 

[muggles]

You're going to need to cut the pipe at the TRV end to get the old nut off, as it won't fit the new valve - they don't make them like that any more. Thus you'll either need a 15×10 or a 10×10 coupler and an appropriate length of pipe to extend back up to the new valve

 

[Savo]

Thanks for getting back to me. That makes sense. I was hoping to get away without having to cut the pipe - I'd been looking at BSPP converters to see if the bottom nut could be connected to the thread of a standard trv with some sort of adapter but couldn't find anything that looked like it would work. I was just trying to avoid having additional connectors as it looks quite messy but I guess it's either that or have TRVs that don't work! I'll probably go with the 15x10 coupler as the TRVs seem a lot more common in the 15mm variety so any future replacements should hopefully be a lot more straightforward.

Thanks again for your help.

 

[sirocosm]

My TRVs look like the one on the top, and even though the pipe is 10mm, there is a small adapter there that brings it up to 15mm. The adapter is soldered on to the 10mm, and you are right it is a bit weird because it has a 15mm outside diameter on one end, and 10mm inside on the other. Although it does not look like it, the bottom on mine was a compression fitting, and the new TRVs with have a nut with a female thread rather than a male. So you will need to get some 15mm olives and pull/cut the old olives off. If the fitting to the rad is 1/2 inch, then you are good to go, but if it is 3/4 (like mine) then you will need to change the tail as well. Usually the new TRVs come with a tail. You will need a radiator tail wrench to get the old tail out, you shove it in the inside of the tail (pipe sticking out of the radiator).

If you like I can post a some pics of one of mine taken apart.

 

[Savo]

Hi sirocosm,

Thanks for the reply - that would be really useful if you have pics of your one taken apart - that will probably help me understand better what is going on - I was looking at the valve not long ago thinking it would help if I knew how the parts of the current valve fit together.

 

[sirocosm]

Here is what mine look like taken apart. The bottom of that copper adapter was soldered onto the 10mm pipe. It was the first time I had seen that type of compression fitting, with a male thread on the nut, and female on the valve. The new ones will be the other way around.

 

[sirocosm]

Here is what it looks like assembled from the bottom.

 

[terryplumb]

You need to cut the supply pipes immediately below the nut and solder on a fitting reducer to each pipe ,10 to 15 mm. And use 15mm valves .
Forget the idea of connecting new valves to what you have , it's a non starter.

 

[sirocosm]

You need to cut the supply pipes immediately below the nut and solder on a fitting reducer to each pipe ,10 to 15 mm. And use 15mm valves .
Forget the idea of connecting new valves to what you have , it's a non starter.

The valve in the picture I posted has a 15mm compression fitting, even though it doesn't look like it (note it has 15 cast in the brass), so a new one will swap right in. The only tricky bit is getting the olive off. I did a few at my place last weekend and there was no cutting or soldering involved.

 

[Savo]

Thanks sirocosm and terryplumb.

The pics were really useful to see what's inside the valve. I'll grab some 15mm TRVs and reducers/couplers so that I can add those in if this pipe is 10mm all the way through. I've not tried soldering pipe fittings before so will probably use a 10x10 or 10x15 compression coupler like the one Andrew mentioned if needed.

Unfortunately the pipes have been painted so looks like I'll have to clean that off before adding the new fittings - what I thought would be a 20 minute swap looks like it's going to bit more messing than anticipated!

Thanks again for the advice and the pictures.

 

[terryplumb]

The valve in the picture I posted has a 15mm compression fitting, even though it doesn't look like it (note it has 15 cast in the brass), so a new one will swap right in. The only tricky bit is getting the olive off. I did a few at my place last weekend and there was no cutting or soldering involved.

What Savo has ,is nothing like what you have.
His lockshield has 10 mm pipe into a 10mm valve ,with 10 mm olive.
The TRV has 10 mm pipe into a 15 mm valve and a mechanical reducer.
What your pic shows is a Yorkshire 10 to 15 fitting reducer,which gets soldered onto the supply pipe. That's what I advised him to use.

 

[terryplumb]

Here is what mine look like taken apart. The bottom of that copper adapter was soldered onto the 10mm pipe. It was the first time I had seen that type of compression fitting, with a male thread on the nut, and female on the valve. The new ones will be the other way around.
View attachment 206528

That is the fitting reducer that was soldered onto your pipe. Nothing like what Savo has.

 

[sirocosm]

What Savo has ,is nothing like what you have.
His lockshield has 10 mm pipe into a 10mm valve ,with 10 mm olive.
The TRV has 10 mm pipe into a 15 mm valve and a mechanical reducer.
What your pic shows is a Yorkshire 10 to 15 fitting reducer,which gets soldered onto the supply pipe. That's what I advised him to use.

So if Savo takes that valve off, what are they left with? just a 10mm pipe sticking out? The TRVs I bought also came with little brass adapters for 10mm.

He will also need a tail wrench because the fitting on the rad looks like it will need to be changed as well.