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Compression VS Sweated Fittings

DonCanDo's picture

I am not a plumber, but sometimes my handyman work has "scope creep" and requires a little plumbing.  Such as re-securing a loose toilet and discovering that the shut-off valve doesn't work.


If possible, I like to use compression fittings in those cases because it's faster, easier and I don't have to worry about scorching stuff like a finished wall.


However, all of the plumbers I've talked to prefer to sweat joints when given a choice.  They claim that it will hold up better in the long run.  Since I've never seen a compression fitting fail, I'm wondering if they're right.  And if they are, what is the typical failure mode of a compression fitting?

(post #108259, reply #1 of 47)

i never see a compresion fitting fail and most homes have compresion angel stops . i would say failure might fail at to high of pressure and or not tightening enough and over tightening cracking nut

(post #108259, reply #4 of 47)

I would say there is much more danger in tightening a compression fitting too much.  Not enough, and it will leak a little, and should be caught easily enough by a little inspecting.  Tighten too much, and the pipe can be twisted, broken, etc.

(post #108259, reply #25 of 47)

Had two compression fittings fail (leaking maybe a gallon an hour) in the first year we owned this house. (We bought it in 1976.) No full failures since, though did have one seepage problem (a drip a minute) with a fitting under the sink, after we replaced the countertop.

Failures are generally due to poor assembly, one way or the other.

I would agree that most homes of recent construction have compression fittings for the angle stops.


The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #108259, reply #2 of 47)

One problem I see occasionally is the nut was tightened to much and the nut cracked.


Last week I took a compression fitting apart and was suprised to see someone had taken the time to solder the ferrule onto the copper pipe. I haven't seen that before.


I do like and use compression fittings, when placed properly, an assembly can be taken apart later if service becomes necessary.

(post #108259, reply #3 of 47)

Try using Sharkbites, I'e had good luck with them.

 

 

Often in error but NEVER in doubt! 

(post #108259, reply #6 of 47)

How do you sharkbite an angle stop?

BruceT
BruceT

(post #108259, reply #7 of 47)

Not a plumber by vocation but, rather avocation. As such, I've never seen a compression fitting I liked. I know they're out there, people love 'em, they work (for awhile) and they're easy. That said, You'll never find one on an automobile or an airplane or any other system requiring reliability.


Leaking water in homes is bad. Compresson fittings are, by design, questionable, at best. Put the two together and I'll have nothing to do with them- they're a failure waiting to happen (if you can get them to seal in the first place).


Every few years, I start doubting myself about these wretched things and decide to try them. To a fitting, I've tossed them and asked myself "what made me think they'd be any different this time". Not a quick learner, obviously...


 

(post #108259, reply #8 of 47)

119639.8 in reply to 119639.7 

Not a plumber by vocation but, rather avocation. As such, I've never seen a compression fitting I liked. I know they're out there, people love 'em, they work (for awhile) and they're easy. That said, You'll never find one on an automobile or an airplane or any other system requiring reliability.


They are common in control systems, like you find at power plants.  Do those require reliability?


 

(post #108259, reply #9 of 47)

I don't know about planes--Jet could answer on that score--but motorcycles and automobiles use flared fittings, mostly because the size of the tubes is too small to make compression fittings practical. (Imagine cranking down with two wrenches on a c-fitting on an eighth-inch tube without torquing the tube all to heck....)


But a flared fitting isn't any better than a compression fitting, and in my experience, compression fittings are damned good. I have never had one fail or leak in 16 years. For anything where disassembly may be a future concern, they are my fitting of choice. (They are also especially valuable in remod work where you have to tie into an existing wet line.)



Dinosaur


How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....


Dinosaur

How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....

(post #108259, reply #16 of 47)

Actually, they use double flare fittings as opposed to the single flare you'll find used with soft copper tubing. Take a critical look at the design of a flare fitting vs. a compression fitting- twice the opportunity to leak.

As for power plants, I can't speak- the stuff is probably (relatively) low pressure, I'd guess- and perhaps should have been clearer in my original comments. "Reliability" really should have been "risk of loss of life". Things like brake systems, control systems on planes etc. where loss of system pressure can translate into, well, loss of life. Airplanes use all manner of fittings- some really wild, expensive stuff (Google "Wiggins Fitting" for starters)- including double flares.

This is sort of academic since the typical water pressure in homes is low and like everyone points out, compression fittings seem to work. Personally, I go for NPT drop elbows and the associated hardware which does allow you to disassemble things at a later date. It's more expensive in every respect but, hey, this is an avocation for me. Bottom line, I suppose, is using what you're comfortable with and works.

(post #108259, reply #30 of 47)

(post #108259, reply #31 of 47)

Here's an exploded view of that wiggins fitting.



Used on the 600 MPH toilet system and the fuel system. Thus low pressure or vacuum side. High pressure is the AN or MS fittings. Hydraulics on an aircraft are in the range of 3000 psi. For the Ram Air Turbine of the Canadair CL65 it's 5000 psi.

(post #108259, reply #32 of 47)

That's a little like sprinkler system fittings.


The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #108259, reply #33 of 47)

"Used on the 600 MPH toilet system..."

Isn't that a little fast for a toilet?

Perhaps only available in Canada; something Red Green might dream up?

:)

BruceT

Edited 5/2/2009 3:58 am by brucet9


Edited 5/2/2009 3:59 am by brucet9

BruceT

(post #108259, reply #29 of 47)

I'll post this to you.


This is an "AN" fitting cut away view.


(post #108259, reply #38 of 47)


Huh. I've got a 2-litre ice-cream bucket full of those things down in the shop somewhere. Thought they were gas fittings; they were in the crawlspace under the house when I bought it in '84.



Dinosaur


How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....


Dinosaur

How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....

(post #108259, reply #28 of 47)


That MS Sleeve is crimped on , therefore a kind of compression fitting.


I'll find more examples as I go. These are on all commercial aircrafts.

(post #108259, reply #39 of 47)

Jet,


It's a fair statement to make, I think, that any of the MS stuff found on aircraft is a far cry from typical consumer grade stuff you might find in a hardware store; not sure trying to draw a comparison is realistic.


Those Wiggins fittings we use everywhere for fuel connections; I mentioned these only to illustrate the variety of fittings used on aircraft.


S.

(post #108259, reply #11 of 47)

1/2" Sharkbite x 1/2 Male NPT to an 1/2" Female NPT Angle stop

 

 

Often in error but NEVER in doubt! 

(post #108259, reply #14 of 47)

Sounds like a lot of extra effort and materials cost, not to mention excess projection from the wall, compared to a compression fitted angle stop.

BruceT
BruceT

(post #108259, reply #15 of 47)

Dahl and Watts both make a "sharkbite" style valve.

(post #108259, reply #19 of 47)

Push on stop and 1/4 turn valves are also offered by Brass Craft and Nibco.


Nothing locks the fitting to the pipe, so the valve can spin on the pipe.

(post #108259, reply #46 of 47)

They make sharbite angle stops. I used one last spring on a cottage in Maine. Perhaps not available everywhere.

(post #108259, reply #34 of 47)

They have them in shark bite configuration.

(post #108259, reply #5 of 47)

A little unconventional, but I use pipe dope around the compression sleeve. I don't have to over tighten them and I have never had one leak. Also use a little on the threads to lubricat them. Wipe off the excess when I'm done so it looks pretty.



~ Ted W ~


Cheap Tools! - MyToolbox.net
Meet me at House & Builder!


Edited 4/30/2009 9:35 pm by Ted W.

~ Ted W ~

(post #108259, reply #10 of 47)

I lube mine as well. I install them very carefully and they usually are fine. When they don't seat well, they drip little slow beads.  


I like the way You can take them off so you can drywall, paint, and then re-instal them.


I've found a lot of water damage behind toilets in the past and it was very helpfull to be able to take them off.


"There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves."
Will Rogers


Edited 4/30/2009 11:16 pm ET by popawheelie

______________________________________________________________ ______________________________________________________________ There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves. Will Rogers

(post #108259, reply #12 of 47)

Ditto

For those who have fought for it Freedom has a flavor the protected will never know.

For those who have fought for it Freedom has a flavor the protected will never know.

(post #108259, reply #13 of 47)

For NPT the sealing is via the interference of the tapered threads. The primary purpose of the dope is to lubricate it so that the threads don't gaul and the friction makes you think that it is tight when it is not.

Compression fittings the seal is the compression of the brass ring.

But I also use a little dope to lubricate them. Other wise the friction can make you think that you are over tightening then when they not tight enough to seal.

FWIW in my area I think that 95% of houses they are compression fittings, that is one that have stop valves and many of them or original construction installations the best that I can tell.

However a surprising number of them don't have any stop valves except on the toilets. They use a soldered right angle adapter that is soldered to 1/4" tubing on the end of the faucet. And this is on houses that are otherwise fairly well constructed.

.
William the Geezer, the sequel to Billy the Kid - Shoe
. William the Geezer, the sequel to Billy the Kid - Shoe

(post #108259, reply #17 of 47)

Compression fittings are capable - with the correct materials, etc. - of amazing performance. Yet, like anything else, if abused they will fail. I have routinely used (appropriate) compression-type fittings in high vibration, extreme pressure, and high temperature settings.


To be fair, a competent plumber can sweat pipe together a lot faster, the parts are a lot cheaper, and you don't need room to swing a wrench.


As for household plumbing, the only time I've used a compression fitting has been when I was not able to remove ALL the water from the pipe - and couldn't get it hot enough to sweat.


The biggest risk to sweating pipe is setting the house on fire.


The biggest problem with compression fittings is that using the wrong wrench ruins the nuts. The main cause of failure is the compression ring not seating properly.

(post #108259, reply #18 of 47)

Thanks.  As I said, I haven't seen any compression fitting failures, but I can imagine how it might happen if not installed properly.  Although, in those cases, it would seem more likely that you would know right away as opposed to having a failure at a later date.


My technique, as others have mentioned is to lube the threads.  I use whatever is handy, pipe dope if I have it, otherwise grease, oil or WD-40.  I figure even vegetable oil is better than nothing (but I do stop shy of asking my customers if I can use their extra virgin olive oil... it just doesn't look "professional").


I'm pretty careful to make sure the ferrule is in the right position before tightening so as not to damage it.  Then I snug it down as tight as I think it needs to be, but I err on the side of not tight enough.  When I turn the water back on, I will snug it a little more if I see any leaks.


It's been working for me, but I don't have a long plumbing background behind me so thanks to everyone for your input.