Leaking compression joint on a rad valve

13 Aug 2007
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United Kingdom
I have a weeping joint on the compression joint on the copper pipe going up to a Rad valve upstairs. I've tightened up the joint but it still weeps, it really needs re-doing.

I have a sealed system, X100 was only put in recently. So the problem I have is in order to fix the joint I'll have to drain off at least half of the system(to get the water level below the level of upstairs).

But I'm also draining off all the X100 and it's £15 a pop. Is there no avoiding it? Other than draining off the system into a load of buckets and then filling it back up with the same water?
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TUrn all rads off, turn system off, bung cold feed and expansion and snatch it. Bit of PTFE or paste. If its a pressurised system then just drop the pressure

BTW make sure when you remake the joint that the olive is not just perched on the end. Should have at least 5mm of copper past it.
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by the way. The weaping is not coming from underneath the nut, but seems to be seeping up the threads and out of the top. Water is sitting on the top of the compression joint nut
bung cold feed and expansion and snatch it.

Don't really know what this means :)

It means if you have a small header in the loft yo block the pipe over the top 22mm and the 15mm outlet on the bottom of it.

This creates a vacumn.

Are you sure its not comin from the tail that connects to the rad then and running down the valve?
yea, it's coming from the tail but not from underneath the nut, above the nut.

Not loft tank, just a combi boiler.

If I close off all the valves to all rads in the house, drain a little bit off the system, will that allow me redo the joint?
JUst open the air vent into a bucket until it stops, close the valves and redo the jiont. Will be fine mate.
when you say air vent, you mean drain valve?

If I open that won't gravity force all the water out? When it stops, the system would be nearly empty
Water can't come out if air can't get in.
Really you need to shut the auto air vent inside the boiler because they do let air in. What boiler is it?
You can let all the pressure out via a rad bleed point, though a drain cock is easier to control. You're expecting maybe 3 litres.
Leave the DC open and it'll suck from your rad when you crack the joint, no loss of water there at all.

Remember to shut the rad valve above the joint!
I appreciate all your help....

I must be immensely thick because I still don't get how the water is going to stay in.

Why would just 3 litres come out and then stop? and where is exactly is that 3 litres coming from?

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