I am in the process of replacing an old radiator in a pressurised CH system. One of the old 15 mm tails had started weeping, so I have shut the valves, and removed the radiator. The old tail was a single component that screwed into the radiator body, with about 30 mm of 15 mm exposed for the olive in the valve fitting to seal onto.
The new 15 mm tail looks almost exactly the same, but is two components, the outer which screws into the radiator, and the inner which is a 15 mm stem that passes through outer fitting, and appears to seal to it with an O-ring.
I'm a little concerned that the O-ring looks like in will be taking all the pressure in the system (I suppose about 1 bar) and that I'm changing out a metal-metal seal for one with an O-ring.
Hi The type of tail you describe is normally sold as a telescopic extension, used when replacing a radiator of a slightly different size. There are other types, the type I prefer (I'm old fashioned) are the same as your old ones, but longer, and can be cut down to fit. I wonder why you need to replace the tail though, the old olive could be removed, and replaced without too much trouble. Nevertheless, the 'o' rings are designed for the job, and should be perfectly OK, there's a lot of those tails in use on all types of systems.
We've just moved into this house, and it's an old system. It looks like the the fitting has been significantly overtightened in the past, and someone has put clear bathroom sealer around the nut in an attempt to stop the drip.
When I remove undid the nut and saw the state of the existing stem and olive, I thought it would be better to just replace them both.
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