Replacing 640mm wide radiator with a 600mm – Can I bridge the gap with extension tails?

[Daviesmith]

Hi everyone,
I'm looking to replace an existing double radiator that measures 640mm wide.
Because of sizing options and availability, I'm considering replacing it with a standard 600mm wide double radiator. That leaves a 40mm overall gap difference (20mm on each side) between the new radiator and the existing floor-entry copper pipework.
My main goal is to avoid draining down the system and altering the rigid copper pipes underneath if possible.
I've seen radiator extension tails (also called valve extensions / rigid extensions) mentioned as a potential solution, but I've never used them before. A few quick questions for anyone with experience:
1. Will extension tails work here? Since the new radiator is 20mm narrower on each side, will adding a 20mm (or adjustable) rigid valve tail extension to each side allow me to connect straight to my existing valves without moving the pipework?
2. Types of tails: What type of extension tails are best for a 20mm gap on each side—fixed length, telescopic / adjustable, or rigid male-to-female adapters?
3. Sealing: What's the best way to seal the threads into the radiator tapping (PTFE tape, thread sealant/Loctite, or rubber O-ring fittings) to ensure no slow leaks behind the valves?
Any advice on whether this is a straightforward DIY fix using tails would be greatly appreciated!
Thanks in advance!

 

[denso13]

1. Will extension tails work here? Since the new radiator is 20mm narrower on each side, will adding a 20mm (or adjustable) rigid valve tail extension to each side allow me to connect straight to my existing valves without moving the pipework?

Yes, normally, if the existing valve takes a 15mm tail. A photo would confirm.

2. Types of tails: What type of extension tails are best for a 20mm gap on each side—fixed length, telescopic / adjustable, or rigid male-to-female adapters?

Get fixed, if too long you can cut them.

Sealing: What's the best way to seal the threads into the radiator tapping (PTFE tape, thread sealant/Loctite, or rubber O-ring fittings) to ensure no slow leaks behind the valves?

Loctite 55, but expensive for one radiator. PTFE would do just fine.

 

[Daviesmith]

 

[Daviesmith]

There's no trvs

 

[denso13]

Ah, no, normal extensions wont work on those, needs to be a 15mm tail,

 

[Daviesmith]

will that fit onto my lock shield valve?

 

[Daviesmith]

I'm thinking of buying something like this https://www.screwfix.com/p/flomasta-700mm-x-600mm-3113btu-white-type-21-convector-radiator/150xp

 

[denso13]

will that fit onto my lock shield valve?

A photo of the other side?

 

[Daviesmith]

It's exactly the same

 

[Daveydub]

Get 2 of these, throw away the nut & olive and see whether 1 or 1 each side makes up the difference best.

Flomasta Brass Compression Adapting Female Coupler 15mm x 1/2" - Screwfix

Order online at Screwfix.com. Female couplers. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

Or

https://www.amazon.co.uk/Radiator-Extension-Tails-Extensions-Millimeters/dp/B0FQCHGDN3/ref=pd_sbs_d_sccl_2_6/525-1881461-2699265?pd_rd_w=dputW&content-id=amzn1.sym.b830a4e4-1d9a-4b95-9151-26f4eef7c6c8&pf_rd_p=b830a4e4-1d9a-4b95-9151-26f4eef7c6c8&pf_rd_r=WPVM25S4XGF349DJK5TG&pd_rd_wg=Gq0pe&pd_rd_r=4b31af1a-8f7d-42ca-b6cf-7bdbb67aacae&pd_rd_i=B0FQCHGDN3&psc=1

 

[gas112]

do not use the telescopic tails they leak for fun

 

[Daviesmith]

do not use the telescopic tails they leak for fun

Sounds ingenious. Pity they have problems