Urgent plumbing issue!

I'm 99% sure that Boss White is rated for potable water, but surely it will say so on the tin or tube.

Traditionally Boss White was used with hemp (although it can be used alone).

These days I tend to use the various PTFE-based thread sealants available from SF and TS (but seldom have issues for potable water so don't usually worry about that). Less messy and easier to dismantle than Boss White type products.

GIYF

Richard

Are you talking about their LSX, or the jointing compound?

No - non potable only. Boss green / supergreen is the one designed for potable / wholesome water applications.

However it sounds like all you need is a spanner to hold the body of the fitting in place while you tighten the nuts.

No, that's the green version

It does. "Boss White Jointing Compound - 400g Tub A non-toxic jointing compound. Conforms to BS 6956-5:1992 for use with hot and cold water (non-potable duties), Natural Gas and low pressure steam up to 7 bar pressure and temperature up to 200°C."

You can't use hemp on potable supplies either (it can harbour microbial growth). PTFE tape would be a more appropriate choice.

Fernox LSX is another silicone based sealer you can use.

You need to stop pretty well any compression fitting from turning when you tighten it.

If concerned about the bit of pipe between two compression fittings turning, tighten on of them until it doesn't turn when you tighten the other.

Sealant on the treads is not the solution - the threads only provide a clamping force. The olive forms the seal. Cleanliness is the most important thing.

Agreed, absolutely. But occasionally you end up with one joint that weeps and where it would be a PITA to replace because of all the other stuff connected to it. And then those PTFE goos are very useful.

It is also one of the reasons I usually use PTFE tape on the threads of new compression fitting builds, because it reduces the friction so that you get a better clamping load with less torque.

People always tell you not to put the tape over the olive, and I don't. Although actually if you compare the strength of PTFE with even fully annealed copper, you will find that a thin layer of PTFE will completely extrude away from the metal to metal interface. The same is true of the "knife edge" that you get where brass olives dig into a copper pipe. PTFE tape there is *not* going to prevent you from getting a seal.

But, in a bodge, it's always possible for tape to trap grit at the sealing location and make things worse.

My bad, it is a very long time since I used it. My first house (in the

I still keep a reel of the Loctite "dental floss" (which I think might be Kevlar) in my "heavy" plumbing tool kit for taper threads. But that works fine used "dry".

I was taught to put tape over the olive. It seesm to work - even 40 years later.

I guess, as in the thread, it acts as a lubricant, The nut has to rotate against the olive so some lubricant doesn't go amiss. I do wonder if grease or a lubricant spray of some sort might be as effective.

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

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 Sod?s 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

Plumbers are, in the main, pretty f****ng stupid.

When I got one to install my *mains pressure* 2.1 bar regulated cylinder, in the loft he nodded approvingly "That will giver you better water pressure"

I can confirm that ptfe does nothing and sometimes makes things worse

PTFE tape has seemingly fixed most of my compression fitting issues for over

I'm still alive too! Brian

Glad it is solved. Often a problem with several bits in series, especially with limited space. I have quite a collection of adjustables, water pump spanners, strap wrenches, and mole wrenches that cover most eventualities. Sometimes an extra pair of hands to hold something "down the chain" helps. There's also an element of "feel" that recognises when something unintended has moved. As you have discovered, sealants give you a bit of margin. Also, for cold water and DHW any very tiny weeps, perhaps only showing up as a damp spot, usually seal themselves quite quickly with lime deposits.

I always add PTFE tape to compression joints after first tightening these days. Quality of fittings just aint what it used to be!

Mike

Absolutely. It may not be needed - but does no harm.