Replacing TRVs on old imperial radiators

[chocolatebar]

Hi,

This is my first post, hello.

I'm trying to do some DIY on my flat and I want to take radiators off the walls to do some plastering.

The radiators are old Imperial types with union tails but some of the TRVs are missing heads and others are stuck closed so I was planning to replace the valves. The pipes are a bit close to the walls to simply replace the radiators at the same time.

I'm having trouble finding new TRVs that would fit. It looks like these would work https://www.cityplumbing.co.uk/p/drayton-angled-trv4-12inch-705153/p/818222 if I can get them to the right height on the pipe to align with the radiator.

I wonder though if I could use the basic version which seems half the price but has a female thread on the bottom? https://www.cityplumbing.co.uk/p/drayton-white-angled-trv4-and-lockshield-valve-15mm-705180/p/536289

Many Thanks!

I've attached some photos of my current setup:

 

[CBW]

Hello and welcome. Personally I would remove the bottom half and renew complete with nut and olive.

 

[oldbuffer]

1. I'd say it rather depends on how many radiators you have to do. The price difference is £16.45, so if its only one or two probably worth saving the hassle and using the more expensive ones.
2. If you want to change to the cheaper valves:
2a. You will have to remove the tails from the radiators and change to the new ones which will come with the valves. You'll need a special spanner such as Screwfix 11467 - four or five pounds.
2b. You will have to change the fitting where the pipe joins the radiator. The ones on your radiators have a hollow nut with a male thread over the pipe. This nut screws into the corresponding female thread on the bottom of the valve, compressing an olive. The more normal ones have an ordinary compression nut over the pipe (with a female thread) which screws onto a male thread on the body of the valve. Again an olive between them. Not an issue in itself, you just remove the old olive and nut and replace with the new ones which come with the valve. There can be an issue of the pipe is not long enough to reach into the new valve, when it would have to be extended.
3. Be aware that is is possible, though unlikely, that the pipes are 1/2" copper. 15 mm fittings can generally be persuaded to fit, but you may have to file / sand a little off the circumference of the pipe to get it to fit. Not difficult, but you need to maintain a circular, scratch free, end to the pipe.
4. You would have to drain the system in either case. I would estimate the time required to actually change each vale as:
4a. 20 - 30 minutes replacing like for like (the more expensive valves)
4b. 40 - 80 minutes if changing to new type valves.

 

[chocolatebar]

Thanks for your detailed and very helpful comments, I learned a lot already.

I ended up finding a cheaper version that should fit the same here: https://www.screwfix.com/p/pegler-white-angled-thermostatic-trv-15mm-x-1-2-/1669v

I did have a question about your point 2a. A lot of TRVs say they are 15mm x 1/2" e.g. https://www.screwfix.com/p/drayton-trv4-white-angled-thermostatic-trv-lockshield-15mm-x-1-2/34362.

Does that mean they have the 1/2" BSP thread on the radiator side same as the screwfix pegler valve? Would those types of valves also be compatible?

Thanks!

 

[mcprinter]

Ref the Radiator spanner. The Screwfix one didn't fit my old Rad Tail

Toolstation have a pair. One of which should fit. One is the same as the Screwfix item

Monument Twin Pack Radiator Spanners | Toolstation

Zinc plated offset handles for radiator jobs. Monument 3in1 and 4in1 Radiator Spanners Made in the UK

www.toolstation.com

 

[chocolatebar]

Is it necessary to remove the tails from the radiator?

Mine are very old Imperial radiators and I would prefer to leave the tails there as the don't leak.

 

[CBW]

Looks like it yes, as the ones you’ve found look a different size to the 3/4” tails you have in already.

 

[oldbuffer]

1. Virtually all domestic radiators have 1/2" BSP female threads into which the tails with 1/2" BSP male threads are screwed.
2. The non-radiator end of the tail will have:
2a. A 15 mm stub pipe, usually chrome plated. These are by far the most common these days.
2b. A union fitting. The nut is captive on the tail, and the valve is threaded 3/4" BSP. The seal is a metal to metal one on gently convex / concave faces.
3. The valve to pipework joint will be:
3a. A standard 15 mm compression fitting. By far the most common.
3b. The type of fitting you have on your old valves as described in 2b of post #3.
4. Out of interest, the threads on 15 mm compression joints are almost invariably 1/2" BSP.

 

[jeff the gasman]

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Order threaded angled valve bodies and other radiator valves at BES.co.uk. Low Prices, Free Next Day Delivery Available, 15k Plus Products in stock. P/N: 17457

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[jeff the gasman]

Sorry this one

BES.co.uk | Next Day Delivery On 15,000 + Plumbing Supplies

Order threaded angled valve bodies and other radiator valves at BES.co.uk. Low Prices, Free Next Day Delivery Available, 15k Plus Products in stock. P/N: 17456

www.bes.co.uk

 

[Fred Blogs]

If your TRVs are working this company sell replacement heads for most TRVs. We have just moved into an 80s build and I replaced all the TRV heads when we moved in as most were broken where the head fits over the TRV. The plastic lugs had gone brittle and broken off.

Replacement TRV Heads

www.heatingcontrolsonline.co.uk