On Wednesday, 23 December 2020 at 21:11:00 UTC, alan_m wrote:
On 23/12/2020 13:32, Tricky Dicky wrote:
I have a situation where I have isolating valves and check valves with compression fittings in close proximity and keep getting a slight weep tightening the compression fittings simply causes problems with the next fitting as tightening it loosens the one below especially when trying to keep the isolating valve orientation correct. So the question is can joint sealants like Boss White be used on potable water?

I need to sort the issue out quick as it is holding up the sink installation after which access becomes more difficult and Christmas dinner is at stake.

Richard

Valves usually have a couple of flats on the body so that you can stop
them turning with a spanner or hold the body with a pipe wrench or water
pump pliers.

Maybe the pipe entering the isolating/check values is not truly on axis
which tends to make the nut on the compression fitting bind on the side
of the pipe when tightening up rather than being easy to turn until the
last 1/4 to 1/2 turn which tightens it. The other possibility for a
weeping compression is that the pipe was not fully seated into the
fitting before initially tightening.

Perhaps on your weeping compression fittings remove the pipe. Is the
olive still loose? Is the olive at the very end of the pipe rather than
10mm+ down the pipe.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk
I went back to the start and the issue is solved. When I realised that a compression 15mm adaptor, an isolator and a check valve all in the space of about 250mm, I realised I might encounter some of the problems so I originally assembled the two assemblies on the bench before putting them in situ. The hot water one proved unproblematic but as posted the cold proved problematic and Sods law it was the nuts on the isolator and the check valve just below that seeped. I did grip the isolator with mole grips while tightening the compression joints but the effect was that as I tightened one the next one loosened. Anyway took the assembly apart retightened all the compression joints on the bench giving each a smear of the Feronox potable water sealant for good measure, reassembled the the whole thing in situ gripping the check valve across some slight flats with the mole grips whilst tightening the lowest compression joint and problem solved. Probably going back to the bench was the crucial task with Feronox sealant as belt and braces. So thanks to all respondents. Christmas dinner is still in the balance, faffing around with the fittings and an unscheduled trip to SF meant I did not get the sink done, so I have tomorrow to drop the worktop in place and fit the sink in but with everything in place and prepared tomorrow should see that done barring any unforeseen issues now I just hope I have not offended the gods of DIY!

Thanks again to all
Richard