Will teflon tape counteract a bad compression ring?
October 30, 2011 6:35 PM   Subscribe

IsMyHouseGoingToFloodFilter: Will a bunch of teflon tape wrapped around a compression ring prevent my toilet shut off valve from leaking?

So, I was trying to replace a leaky angled shut off valve coming from my wall to a toilet (Something like this). After removing the old shut-off valve, I was unable to remove the old compression ring. After struggling with it, I decided to see what would happen if I put the new shut-off valve on using the old nut and compression ring. When I turned the water on there was a good deal of water coming out around the nut and the compression ring. The only solution I was able to come up with was to wrap the compression ring and the new valve threads with lots of teflon tape. When I reconnected everything, it did indeed stop the leak, but I'm a bit worried that this may not be a tenable solution.

My question is whether I can rest comfortably with my teflon tape solution (short term? long term?)

A second question: A search through other forums indicates that I could use a compression sleeve puller to remove the old compression ring. Has anyone had any experience with one? If I were to pull the old compression ring this way, could I then reinstall the valve with the new ring, or will the pipe be damaged in some way?

Please help me sleep tonight!
posted by i love cheese to Home & Garden (8 answers total) 1 user marked this as a favorite
It depends on why the original was leaking. There's only a few ways a compression fitting can leak. Is the supply pipe straight on the inside and the old ring (ferrule) intact? If so, then the reason it was leaking was probably just that it wasn't tight enough. In that case, you probably can re-use the ring (though it may have been a waste of a new shut-off valve). The secret in plumbing is to tighten everything until just before it breaks, but have you tried tightening the nut slightly without the tape? I know it's a pain to have to turn the water off again, but you can remove the tape, tighten the nut, turn on the water, and tighten slowly, gently but firmly (a crescent wrench of the proper size helps enormously with accurate tightening) until it stops leaking. It's possible that this process will cause the ring to collapse the pipe, but hopefully it will just stop. Keep a rag handy so you can wipe the fitting dry after each increment.

If the pipe does collapse, it's not the end of the world. A mini pipe cutter can take off the bent section, and then you can start fresh. Obviously, if your stub is already short, this may not be advised, because you might end up having to solder on a new stub, which could mean cutting away some drywall and/or moving the toilet temporarily.

Having said that, I had good luck pulling an old ferrule with a pair of vice grips. I adjusted them so that they would just grip the ferrule, and pulled straight off. As I understand it, pipe dope (sealant) only interferes with compression fittings. You will find real plumbers who use Teflon, but the conventional wisdom is that it is not necessary.
posted by wnissen at 7:12 PM on October 30, 2011

Teflon tape is to make pipe threads, which seal by the actual threads deforming against each other as you tighten, easier to tighten. It has no sealing properties. Using teflon tape as a packing material for a compression joint is asking for trouble.
posted by notsnot at 7:25 PM on October 30, 2011

Best answer: I've rarely bothered to remove a brass ferrule from a copper pipe when replacing a compression fitting. The ferrule will remain locked to the copper pipe and will generally reseal to the new fitting. The only got ya assuming everything looks to be in good shape is when the length of free copper pipe after the ferrule is too long to allow the ferrule to seat against the sealing seat of the fitting (IE: the end of the copper pipe bottoms out before the ferrule makes good contact with the sealing surface).

You can see if this is the case by installing the fitting but not covering the ferrule with the nut and then observing whether the brass ferrule is making contact. If this is the problem you can use a pipe cutter or a file (or a dremel) to remove some of the excess pipe and allow the ferrule to make good contact.

And ya, teflon tape shouldn't be used on flare or compression fittings; you are just asking for it to blow out and resume leaking.
posted by Mitheral at 8:30 PM on October 30, 2011

Never use teflon tape on anything other than a threaded fitting. Using it on a compression fitting is asking for trouble. I agree that the reason it is leaking is that it probably wasn't tight enough, but check the length of the pipe protruding past the sleeve as mentioned my Mitheral. Make sure that you also hold the tap to prevent it from turning if you can so you don't risk starting another leak on the other side of the tap by bending the pipe.
posted by dg at 8:42 PM on October 30, 2011

I've solved the same problem that you are working on by cutting a small amount off of the existing pipe, removing the old compression ring (which will slide off easily once you cut off the end of the pipe that's been subject to compression), and then using a new one. I do the cutting using a little tubing cutter, not a saw. Also don't forget to de-burr the joint before putting the new sleeve on.

Of course there is a limit to how many times you can perform this operation before you'll be out of pipe, but if this is the first time the valve has been replaced you should be good.

Also ... 1/4-turn shutoff valves are superior in basically every way to the old multi-turn valves. I wouldn't use anything else anymore.
posted by Kadin2048 at 9:15 PM on October 30, 2011

In the long run you are best to replace the valve with one that is soldered to the copper pipe-if the joint is not 100% they can blow off with pressure spikes (I have seen this many times-usually people were scared to tighten too much).

Many plumbers wrap the brass ferrule with teflon tape to enhance crushing of the ferrule-this is why your valve sealed with the teflon-the lubrication it provides allowed the ferrule to crush smoothly into the shape of the ferrule seat.
The best way to tighten a larger compression fitting like this is to use 2 decent crescent wrenches -one to hold counteract the tightening force and one to tighten the nut.Too many people either do not use stable wrenches to tighten this type of joint properly-or they tighten it too much-it takes awhile to get the feel for the right tightness.

If you need to pull a ferrule-you don't really need a puller-you can use a crescent wrench set to the copper pipe size(perpendicular to the copper and between the jaws) and tap/slide it lightly towards the end of pipe with a hammer OR use a hack saw blade and score the ferrule but not the pipe.

Teflon is used to lubricate threaded joints-these pipe threads are tapered (NPT)and THAT is what seals the joint-the teflon allows for a better seal as it lubricates the joint to allow a tighter connection.It may seem that teflon plus the threads to seal but one only needs to run some high pressure(ie 300 PSI +) or high heat mediums to see the teflon spit out of a poorly created joint.There ARE pipe dope compounds that will seal the threads but teflon is meant for lubrication...it also works for ferrule lubrication as this poster found out.
posted by plumberonkarst at 10:22 PM on October 30, 2011

And lastly, you could always swap out the tank side of the valve (where I understand the compression fitting is - that is to say the part between the valve and the toilet tank) with a stainless-wrapped hose. Not that expensive anymore, easy to install properly.

(Though, in my experience, if the joint has held so far (and you haven't used a crazy amount of teflon tape (like not more than four wraps, about)) it's likely good for the next indefinite while - this said without looking at the actual set-up is completely ridiculous, actually, but in theory I'm comfortable saying that).
posted by From Bklyn at 1:09 PM on October 31, 2011

Response by poster: All good answers. Thanks everyone. I had a plumber come today and fix it properly. He ended up cutting a bit of the pipe off to make everything fit.

Fortunately, my ill-conceived solution survived long enough.
posted by i love cheese at 5:28 PM on October 31, 2011

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