flood from failed compression fitting w/pex

homeboundJune 16, 2011

One of my clients has a newly-constructed house and is now dealing with a sizeable flood only about a month after they got their CO and moved in. On the first floor, a pedestal sink apparently had one of its pex supply lines essentially slip out of the compression ring of the angle stop and spray water all night long (couple hundred gallons estimated). Much of the hardwood is damaged from water that traveled through the subfloor.

Interestingly, this house has had the water on for months, including that sink, so everyone (builder, plumber) is wondering why it didn't leak until this episode and say they haven't seen it ever happen like this before. Anybody ever come across a similar situation?

The homeowner is rattled, as you can imagine, wondering if other connections are suspect. I think it's just that the compression nut wasn't tightened enough to compress the vinyl ferrule, and that it was just bad luck that it didn't leak until this happened. Anybody seen a similar issue with pex supply lines? Thanks. BTW, the supply coming out of the wall is plastic (pex or cpvc?) has a lot of play and may not have been clamped to a stud nearby. Seems that way, anyhow.

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Correction: I meant to say that it slipped out of the compression "nut".

    Bookmark   June 16, 2011 at 9:36AM
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"compression 'nut'"

Sounds like a defective install.
PEX normally uses compression rings to attach to fittings.

    Bookmark   June 16, 2011 at 11:38AM
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Brickeyee is on the point. ALL "PEX" piping uses some sort of Barb fitting with a compression ring. I have never ever heard of a single failure with this type system. Compression fittings use a ferrule either brass or plastic. The brass ferrule bites into the pipe wall, but the plastic ferrule does not. It is not a surprise to me that a "Compression fitting" which has a plastic ferrule failed. All domestic water plumbing systems are required by code to be pressure tested, which may have revealed this issue. Was the system tested?


    Bookmark   June 16, 2011 at 1:25PM
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Compression fitting on flexible line (plastic) normally have a metal insert for the line that give the line enough strength to stand up to the compression force generated as the fitting is tightened.

    Bookmark   June 16, 2011 at 4:52PM
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Sorry, but maybe I'm totally botching the terminology here.

These are the plastic supplies from faucet body to the angle stop, typically cut to fit (similar to copper tubing back in the day). (Is that pex or just some other plastic supply? They are typically found in the stores along with the braided supply lines, etc.)) Each is sold with a plastic/nylon ferrule, which presumably is used under the nut when connecting to the angle stop. Right? And please reconfirm if the metal inserts are used with those types of plastic supplies. Thanks again for your help in understanding this.

BTW, the builder apparently is going to rip out a lot of new hardwood and drywall below due to this fiasco.

    Bookmark   June 16, 2011 at 7:17PM
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PEW is the plastic plumbing in the walls. The little plastic supply line from the shutoff to the faucet is not PEX.

In my old house, we had one of those compression fittings on the toilet supply line blow when we were out of town for the day. We had lived in the house for several years and hadn't had any problems. It had the metal insert, but it didn't matter. It ran all weekend and cause about $6,000 in damage.

    Bookmark   June 17, 2011 at 8:58AM
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Coming full circle, here.

It turns out they are, in fact, "pex risers" (check out google). They come in light grey or white. While they are sold with a nylon ferrule, one is also supposed to use a metal insert (stainless steel or brass) which makes you wonder why the insert doesn't just come with it, too.

Here is a link that might be useful: Pex riser

    Bookmark   June 18, 2011 at 9:13AM
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I had this happen just tonight. Luckily for us, we were home. The tubing just blasted right out of the compression nut. Don't yet know why, if I didn't tighten it enough or what. There was no damage to the ferrule, so not having the metal insert didn't have anything to do with it.

    Bookmark   July 4, 2011 at 12:22AM
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Thats why you spend (or have the builder spend) the extra $4 and install the braided hose which have deep threaded compression fittings.


The reason they don't:
$1.48 for the plastic rise vs. $5.28 for the braided hose

    Bookmark   July 5, 2011 at 8:04AM
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The polymer braided hoses are not much better than the pex riser.

If you want to know it won't leak then use a copper riser instead of the pex one or use REAL stainless steel braided hoses which are much harder to find and more expensive.

    Bookmark   July 5, 2011 at 11:11AM
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Even the stainless steel braid lines are at best a false sense of security. While it is true that the stainless steel braid will prevent the line from rupturing from excessive pressure, ask yourself, what is the likelihood that the pressure in your house would ever even reach the blowout pressure for the line? Under that impressive looking stainless steel braid, most of those lines have a simple neoprene or polyehtelene hose. Now it is true that they offer a 10yr warranty, but then that is about the expected lifespan of neoprene hose anyway.

On the other hand, you can get a straight length of chrome, nickle, polished copper or gold plated brass supply tubing for about $3. The compression ferrule for the bottom end comes pre-packed in the angle stop compression fitting, and even if you are replacing a line and need to purchase a new ferrule, they are only a nickle.

The cone washer and brass friction washer for the faucett connection come pre-packed in the faucett set and most ppl just throw them away.

The down side is that you will need a tubing cutter to cut the line to length, but then no real plumber is properly dressed in the morning until he/she has their mini-cutter in their pocket and the cutter should be mandatory in any homeowners tool kit.

I will admit that when using the brass tubing you often have to bend it to fit but if that is the case you can get the beaded type line, which looks like a string of pearls and can be hand bent without tools, or you can get an in-expensive tubing bender and keep it in your tool box for future use. (You can often find an inexpensive tube bender on the el cheapo tool table at your local autoparts store for under $3).

The upside is that while the braided line has a 10yr warranty, if you install the brass line it will still be working fine when your unborn grandchildren are retired.

Ask yourself this question, if those braided lines were as good as some seem to think, why are they prohibited in commercial plumbing?

    Bookmark   July 5, 2011 at 1:48PM
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I don't think the complaint is that the tubing blows out. I guess that is possible, but unlikely. The complaint is that the compression fitting fails. When it fails - oh boy, does it fail.

    Bookmark   July 5, 2011 at 6:21PM
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When installed properly the compression fittings are every bit as reliable as a threaded fitting.

    Bookmark   July 5, 2011 at 6:40PM
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I too have experienced a pex supply line slipping out of the connection nut. Two weeks after a bathroom remodel we woke in the middle of the night to find water everywhere. End result ~$40000 of repairs and two months out of the house. It appears the plumber didn't sufficiently tighten the connection nut (once the connection nut was detached the plastic ring could slide up and down the pipe freely and would drop off if allowed).

I came here as part of an attempt to establish whether I should have a plumber re-install pex or use braided lines - one plumber says always use braided, another says pex are excellent and braided have their own problems.

    Bookmark   September 27, 2011 at 9:55AM
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The cheap braided lines at the box stores are not what consumers think they are. They are merely vinyl lines with vinyl braid and a clear sheath. They are not the Aeroquip SS lines that appear on race car brake systems and seen in high pressure hydraulic environments. IMO they are not as reliable as a copper line with fittings.

I'd ask the plumbers whether they have Pex or braided lines in their own homes and their parent's homes and hope for an honest answer.

    Bookmark   September 27, 2011 at 11:34AM
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Clearly the problem was installation. Compression fittings with ferrules require a certain "feel" to know when they're right. Are there any among us who hasn't messed one up and had to do it over? They're inexpensive and they do, indeed, work quite reliably when installed properly.....but they certainly are easier to make mistakes with, as apparently happened here.

Braided lines with screw-and-gasket seals are easier to get right the first time but, as stated, they, too, can have their issues. Must say, though, that I've personally never messed one of those up and I've never had one fail.

    Bookmark   September 27, 2011 at 1:36PM
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I've seen quite a few pacific rim cheapie braided lines puke and always where the fitting is crimped on to the outer braid. Failure is a tiny dribble followed up by a flood.

When it comes to compression fittings on Pex, copper, or anything else, it is the same as any other job... all you need is the knowledge and the tools. Lacking either invites less than a satisfactory outcome.

That's one danger when making professional tools available to the novice... they don't come with the knowledge on how to correctly use them.

When pros pooch a fitting they are responsible for the damage and that's why they are licensed and bonded but if you hired a handyman (woman) or did it yourself there's no one else to blame.

Pex is neat stuff till rodents chew though it ;-)

    Bookmark   September 27, 2011 at 2:07PM
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"Failure is a tiny dribble followed up by a flood."

I suspect there are likely many here who know exactly what you mean!

    Bookmark   September 27, 2011 at 4:45PM
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Posted by lazypup on Tue, Jul 5, 11 at 18:40:

"When installed properly the compression fittings are every bit as reliable as a threaded fitting."

What is the proper torque, or "additional turns after hand-tight", for 3/8" Pex riser with plastic ferrule? Been searching the internet for over an hour and can't find a spec anywhere.

    Bookmark   October 23, 2014 at 10:45AM
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