I'm at my wits end with this corrugated copper pipe. How to stop this leak?

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SonOfGloin

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I'm hoping to tap the collective wisdom of the seasoned vets here. I'm in the middle of a water heater replacement project and I opted to forgo sweating in rigid copper piping and using a union and instead set it up to accept flexible copper pipe for ease of future replacements.

I cannot, for the life of me, get this last nut to seal!

No matter what I do, it leaks through the threads. I avoided using teflon tape, as seems to be the common advice on this forum over the years. I put a small amount of silicone grease on the rubber washer for good measure. No different. Any level of tightness from hand tight to full muscle/two wrenches tight yields the same result. I followed up by trying the teflon tape - no difference. I even bought a different corrugated pipe, thinking something was off in the manufacturing process of the old one. Still the same result.

The male threads do not seem to be stripped or anything, either.

What's the trick with these damned things? This is my first time working with them. Thus far, I am not impressed. I've spent hours finding with this damned thing...

Any help is deeply, deeply appreciated.
 

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Tuttles Revenge

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Usually I would blame the cheap nuts on flexes as the most likely culprit. If the threads on the inside of the nut aren't truly machined or machined poorly, they will not allow you to tighten well on the adapter. But I don't think silicone grease is recommended on the washer as I would think it could make it slippery and gush inwards. What does the face of the copper male adapter look like? Totally Flat? If not, run a large Mill / Bastard file over the face to make it completely flat. I do put a single wrap of teflon tape on my threads which simply reduce the friction and allow the nut to tighten with less wrench force.
 

Jeff H Young

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I dont like the way those tighten up and just putting them on dry you gotta really bear down, lubricating washer I dont like . I usually put a light amount of dope away from ends, I just hate to see tape, but Tuttles way is fine , a wrap wont hurt a thing.
I was thinking could be a solder drip on end of adapter, washer could be damaged ?
 

SonOfGloin

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Thanks for the swift replies, guys. I'm taking cold showers until this gets resolved :)

Very interesting thoughts. First, I'll wipe off the silicone grease from the washer - easy peasy. I tried it because I saw it mentioned in an old thread here but I agree that this might make it prone to slipping.

Tuttle, to your question about the face of the copper male adapter, it seemed perfectly smooth to me, but once I took a photo for you and looked more closely, it does seem to be a bit asymmetrical, no?

Jeff, interesting idea about putting a light amount of dope a few threads away from the end. Definitely wouldn't touch the washer this way. Any problems with water getting past the washer, but held back by the dope only?

So I suppose I have to decide whether to do the single layer of teflon tape for lubrication, or use the dope. Hmm
 

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Tuttles Revenge

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A rubber washer is meant to make up for slight deformation in mating surfaces... but the washers in water heater flexes can sometimes be near as hard as plastic.

My gut instinct is that the threads are popping due to poorly constructed teeth on the nut.
 

Fitter30

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Brand and model of the flex connectors . Pic of the package would help. Don't think their made for pipe thread. Looks like they need a brass adapter.
 

Reach4

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I wonder if the washer on the top of that flex line is damaged. Maybe turning it upside down would work around this. Or maybe a replacement washer would do it.

Also, is there a nick on the bottom of that copper adapter? Feel it by dragging a finger nail.
 

John Gayewski

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I second the file method. You need a smooth flat surface for the washer to mate up to. The threads should see no water. Using grease on this particular washer can cause it to slide away from the mating surface, as others have said. You might also need a new washer at this point if you have torqued down on this washer once and pitched it real good, it could be junk now.

Interestingly when you buy a Navi link kit and they send you a header system and valve kits. Those kits come with close nipples that are machined flat on one side. It's hard to spot and some are machined better than others. Who would think that you could put a nipple on backwards? But these Watts valve kits come with these special nipples. Just a weird note for anyone interested.
 

Jeff H Young

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I could understand there maybe flexes made for straight threads and not tapered that would mate to a proper nipple with a nice flat land on the end. but I dont know of them hooking up special equiprtment or a higher pressure application seems could be stuff like that but dont recall that type flex.
 

SonOfGloin

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A rubber washer is meant to make up for slight deformation in mating surfaces... but the washers in water heater flexes can sometimes be near as hard as plastic.

My gut instinct is that the threads are popping due to poorly constructed teeth on the nut.

These washers are fairly robust and malleable, thankfully.

Brand and model of the flex connectors . Pic of the package would help. Don't think their made for pipe thread. Looks like they need a brass adapter.

I actually tried two different flex connectors. No supply house stuff, though; One from Blue (Apollo brand) and one from Orange (Everbilt brand). Your comment about brass is really interesting. Did I mess up this install by sweating in copper pipe thread? I never encountered any indication that I will need to use brass in order to use flex connectors. Should I have used a 3/4" sweat x 3/4" mpt adapter?

Interestingly, the other flex pipe sealed perfectly on the first shot. This one threads into the same type of pipe thread adapter.

I wonder if the washer on the top of that flex line is damaged. Maybe turning it upside down would work around this. Or maybe a replacement washer would do it.

Also, is there a nick on the bottom of that copper adapter? Feel it by dragging a finger nail.

I effectively ruled this out - when the apollo brand flex connector from Lowe's leaked, I swapped out the washer with one from a broken flex pipe (don't ask. Clumsy day) and still experienced the same leak through the threads.

The bottom of the copper adapter is smooth.

I second the file method. You need a smooth flat surface for the washer to mate up to. The threads should see no water. Using grease on this particular washer can cause it to slide away from the mating surface, as others have said. You might also need a new washer at this point if you have torqued down on this washer once and pitched it real good, it could be junk now.

Interestingly when you buy a Navi link kit and they send you a header system and valve kits. Those kits come with close nipples that are machined flat on one side. It's hard to spot and some are machined better than others. Who would think that you could put a nipple on backwards? But these Watts valve kits come with these special nipples. Just a weird note for anyone interested.

Hmm interesting info on the nipple. That might support the need to file this down and make it flatter.

I could understand there maybe flexes made for straight threads and not tapered that would mate to a proper nipple with a nice flat land on the end. but I dont know of them hooking up special equiprtment or a higher pressure application seems could be stuff like that but dont recall that type flex.

It's worth noting that these flex pipes have no problem whatsoever mating to the WH's nipples.

4 to 6 wraps of tape will solve the problem. It's not against the law to use tape on a fitting that has a washer.

I already tried with 5 wraps. It leaked this way too.
 

Jeff H Young

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Give it 10 wraps and pray! but I call it improper and shoddy but a good temporary. Tuttles single wrap was just to allow it to tighten but 6 wraps is silly but till you can do it right ok. I think I mentioned the threads arent supposed to seal anything
 

SonOfGloin

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Give it 10 wraps and pray! but I call it improper and shoddy but a good temporary. Tuttles single wrap was just to allow it to tighten but 6 wraps is silly but till you can do it right ok. I think I mentioned the threads arent supposed to seal anything

Prayer is my primary strategy on this :).

A good temporary is what I'm shooting for. I'm dying for a hot shower. I'll try Tuttle's method (file down then single wrap for an easier tighten with a new washer. Otherwise I'll go crazy with the tape.

What do you recommend I do for a permanent solution?
 

wwhitney

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The seal is supposed to be the washer between the flat flange of the flex at the bottom of the nut and the flat end of the MIP adapter.

So if the there's a thread incompatibility (maybe a bad or poorly formed MIP adapter) that causes the threads to get tight before the washer can compress, you won't get a good seal. That's also why teflon tape on the theads is not a good idea; it will just increase the chance the threads get tight before the washer is compressed.

To diagnose, I suggest hand tightening the nut without any washer and noting how far it goes on. Then hand tighten with the washer and see if it's the same. Ideally you should be able to hand tighten the nut without a washer pretty far, and then find that if you put a washer in, it gets tight sooner. as the washer starts to compress. In which case you might go hand tight plus a 1/4 turn as a first attempt, and tighten a little more if it leaks.

If the threads are binding before you get the washer compressed, you could try a couple different work arounds. You could use two washers, that's more of a temporary workaround or diagnosis tool. You could change out the MIP adapter. You could get a brass nipple that you can bottom out by hand in the nut, and then put it on with a brass coupling with dope/teflon tape in both the coupling joints. You could chase the MIP adapter threads with a die to see if the threads are oversized or malformed. You could try tightening the heck out of the nut and the MIP adapter with no washer, to deform one or the other to allow the threads to engage more, so that when you do put in a washer it will compress properly.

Obviously some of those may damage the MIP adapter or the flex, so be prepared with replacements as required.

Cheers, Wayne
 

SonOfGloin

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I followed Tuttle's lead and filed down the base of the threaded adapter. Got it good and flat:

IMG_6390.jpg


IMG_6391.jpg


Flipped the washer to get a nice new surface on which to seal. Wrapped in a single round of teflon tape for lubrication. Same result - leaks at the threads
 

SonOfGloin

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The seal is supposed to be the washer between the flat flange of the flex at the bottom of the nut and the flat end of the MIP adapter.

So if the there's a thread incompatibility (maybe a bad or poorly formed MIP adapter) that causes the threads to get tight before the washer can compress, you won't get a good seal. That's also why teflon tape on the theads is not a good idea; it will just increase the chance the threads get tight before the washer is compressed.

To diagnose, I suggest hand tightening the nut without any washer and noting how far it goes on. Then hand tighten with the washer and see if it's the same. Ideally you should be able to hand tighten the nut without a washer pretty far, and then find that if you put a washer in, it gets tight sooner. as the washer starts to compress. In which case you might go hand tight plus a 1/4 turn as a first attempt, and tighten a little more if it leaks.

If the threads are binding before you get the washer compressed, you could try a couple different work arounds. You could use two washers, that's more of a temporary workaround or diagnosis tool. You could change out the MIP adapter. You could get a brass nipple that you can bottom out by hand in the nut, and then put it on with a brass coupling with dope/teflon tape in both the coupling joints. You could chase the MIP adapter threads with a die to see if the threads are oversized or malformed. You could try tightening the heck out of the nut and the MIP adapter with no washer, to deform one or the other to allow the threads to engage more, so that when you do put in a washer it will compress properly.

Obviously some of those may damage the MIP adapter or the flex, so be prepared with replacements as required.

Cheers, Wayne

Your intuition is spot on here, Wayne. I followed your suggestion and threaded the flex pipe without the washer installed, and it does indeed encounter resistance at the exact same spot (with about three threads showing). In fact, I wasn't able to muscle it further without feeling like I'd ruin a downstream joint (even with the second wrench in hand), so I decided not to press my luck trying to use the nut to re-form the threads in the MIP adapter.

Interestingly, I just tried the two-washer method and, as expected, I encounter resistance much sooner in the threading process. I tightened it down good and, much to my surprise, the leak still persists through the threads. The universe is conspiring against me and my plans to take a shower tonight. Further, I just developed a pinhole leak in one of the flex pipe's corrugations. That's two wasted flex pipes. This is getting expensive... I have a stainless one as a spare at least.

If I go down the route of replacing the adapter, is there a brand you recommend? I've only seen this (3/4" sweat x MIP) in copper. Does it exist in brass? For what it's worth, I just tried threading the flex pipe into a spare MIP adapter (the same one that's sweated in place in my pics) and the threads encounter resistance around the same spot; I'm not able to full thread it without a washer in place.

The brass coupling/nipple idea is an interesting one. This would also drop things low enough that I could probably switch to 18" corrugated pipe, too.
 

SonOfGloin

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Well, interestingly, I was able to chase the threads on the MPT adapter - it just took a little more elbow grease on the flex pipe nut without the washer installed. I can now completely bottom it out by hand - it doesn't bind anywhere. I was super confident that this would be it. I reinstalled the washer and was able to tighten it farther than ever, and it now "feels right".

I opened up the ball valve and...



.... the damned thing still leaks at the threads
 

wwhitney

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Well, interestingly, I was able to chase the threads on the MPT adapter - it just took a little more elbow grease on the flex pipe nut without the washer installed.
Note that when doing that you need to use two wrenches, one on the adapter to hold back, and one on the nut. That's also true for tapered joints that seal, but shouldn't be true for the final washer joint once you get that figured out.

I can now completely bottom it out by hand - it doesn't bind anywhere. I was super confident that this would be it. I reinstalled the washer and was able to tighten it farther than ever, and it now "feels right".

So if the end of the male adapter has a flat end that is suitable for sealing (check the washer against the end, check for any deep scratches of the copper), the washer is in good condition, the flat flange end of the corrugated pipe is similarly without defect, and the joint can be tightened enough, it shouldn't leak. Overtightening can cause a leak by deforming the washer too much.

Given where you are now, try 2 washers again. If you aren't overtightening now, It is conceivable that the male adapter doesn't have enough threads on it to allow the washer to compress. In which case you'd want to change out the male adapter. Perhaps to another configuration. Or one you can test in the flex before installing it, to check that the washer compresses.

Cheers, Wayne
 

Jeff H Young

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Dang with your luck get a pushfit x 3/4 fip water flex LOL thats gotta work cut that adapter off . But Id just have to figure it out
 

SonOfGloin

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Sure seems to be compressing nicely against the washer:

IMG_6393.jpg


The copper also doesn't have any deep scratches.

I'd be surprised if the male adapter doesn't have enough threads to adequately compress the washer. The other line is attached to the same adapter, and it sealed perfectly on the first shot (hand tight, plus moderate wrench turn). This non-leaking joint isn't threaded as far as I've been able to go with the bad one.

I'll try the two washer method again.

Also, for what it's worth, I got it down to a pinhole leak with 8 wraps of teflon
 
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