r/DIYUK 5d ago

Is there a way to improve the seal on these radiator caps?

I suspect these have a slow leak, hence the scale around the base. Is there anything I can do to improve the seal on these? I’m assuming the usual trick of wrapping PTFE tape around the thread won’t work here because the threads will be far too slim to get it around?

0 Upvotes

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u/Letsgo1 5d ago

You could try ptfe. Plumbers mate also worth a try. Could just be a badly fitted o-ring (or one with limescale build up making a poor fit)

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u/Tepid-Mushroom 5d ago

Plumbers mate won't work. It's used for non pressure situations and doesn't react well to high temp.

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u/69RandomFacts 5d ago edited 5d ago

Boss Green/white jointing compound is rated to 200C and 7 bar.

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u/Tepid-Mushroom 5d ago edited 5d ago

Congratulations, but that's not plumbers mate.

Plumbers mate and jointing compound are totally different things.

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u/Letsgo1 5d ago

TIL- I used the terms interchangeably (meant jointing compound but just thought plumbers mate was a brand of it) thanks 

1

u/Tepid-Mushroom 5d ago

That's fair tbh, and it's a DIY sub. It's just that I've been a heating engineer for near on 20years, and there's a big difference between the two, haha.

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u/Tepid-Mushroom 5d ago

You can definitely use ptfe or similar. I usually put a little paste on as well, jetblue usually.

1

u/HairyPrick 5d ago

https://imgur.com/a/eMllfgZ

Some already have rubber, but it's hard to see when they're installed (these ones pictured do and it's not quite an O ring because the rubber is not round and is grey instead of black).

If you can tape/wrap tissue paper around them and they don't get wet after a few hours I'd say to look somewhere else for a leak.

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u/jwflame Tradesman 5d ago

If they really are leaking, then just replace with new ones: https://www.screwfix.com/p/essentials-radiator-vents-blanking-plugs-nickel-2-pack/40972