Shut-off valve: sweat vs compression

[French_guy]

I had a plumber to do some work at my house, and he said he only install sweat valves, because the compression type can come-off.....
What do you think? is a compression valve "safe" to install?

 

[SteveW]

Valves for what purpose? If for small-diameter pipe, like for a toilet or faucet shut-off, it is pretty standard to use compression fittings. They do NOT come off spontaneously if installed correctly -- the brass ferule actually gets compressed into the pipe so really can't come off on its own.

For larger pipes, like 3/4 or 1", the pros on this site say "No" as these can in fact come off if the pipe is jostled.

 

[Sponsor]

 

[French_guy]

Shut-off valve for a bathroom faucet.....on 1/2" copper pipe

 

[SteveW]

1/2" should be fine.

 

[French_guy]

Should be?

 

[SteveW]

Yes, compression valves are put on 1/2" copper pipe all the time so should be OK if properly installed.

 

[French_guy]

Any tips for a good installation?
Other question: what about the Sharkbite style?

 

[SteveW]

For compression valves, make sure the pipe is round (not distorted), and smooth (no gouges). Put the nut on the pipe then the ferule. Do not use tape or pipe dope on the threads -- if anything, 1 or 2 drops of household oil on the threads (I do this, some of the pros do, most probably don't). Tighten until you can feel the ferule distort a little into the pipe -- you develop a feel for this after you've done it a couple times. Turn the water on and check for leaks. If there is a leak, tighten up just a very little bit and check for drips.

Also, when you tighten the nut, make sure you use a 2nd wrench on the valve to "hold back" as the pros say.

RE: Sharkbite, I did use one Sharkbite shutoff valve in one of my bathrooms for a pipe that I couldn't solder. Has worked well for 5+ years. I don't think the pros particularly like them but I think they have their place.

 

[Terry]

It takes a puller to remove a compression stop.
I have never, ever, seen one come off.

All we use here is compression.

 

[French_guy]

A cap was welded on top of the stub-out, and some solder went onto the pipe below.....How do I make sure the pipe is smooth enough for a compression fitting?

 

[SteveW]

You can probably sand it off with emery paper (find it in the plumbing section of your favorite hardware store.)

If you have a propane torch and it's safe to do so, you can heat it up and wipe off the solder while it's molten.

 

[French_guy]

For compression valves, make sure the pipe is round (not distorted), and smooth (no gouges). Put the nut on the pipe then the ferule. Do not use tape or pipe dope on the threads -- if anything, 1 or 2 drops of household oil on the threads (I do this, some of the pros do, most probably don't). Tighten until you can feel the ferule distort a little into the pipe -- you develop a feel for this after you've done it a couple times. Turn the water on and check for leaks. If there is a leak, tighten up just a very little bit and check for drips.

Also, when you tighten the nut, make sure you use a 2nd wrench on the valve to "hold back" as the pros say.

RE: Sharkbite, I did use one Sharkbite shutoff valve in one of my bathrooms for a pipe that I couldn't solder. Has worked well for 5+ years. I don't think the pros particularly like them but I think they have their place.

So once I can't tighten it anymore by hand, should it be something like 1/2 turn more with a wrench, that's it?

 

[SteveW]

It's something like that -- not an exact amount of turning per se, as I'm sure you know, but more of a feel for it being appropriately snug. If it gets overtightened, it will actually leak due to that. So, yes, finger tighten, then use 2 wrenches to tighten further until "snug." Then see if it leaks.

 

[Terry]

You will need more than a half turn after hand tight. I snug them pretty good.

 

[French_guy]

I'm still reading people recommending to use dope or teflon tape......I thought they were meant to be use without all of that........!!!

 

[SteveW]

Absolutely meant to be used without either tape or dope. Tape and dope are intended for tapered pipe threads -- in other words, threads that are actually used to seal a pipe and be watertight. The threads on a compression fitting are not intended to be watertight, only to clamp the pipe/ferrule combination into the fitting.

 

[French_guy]

Yep, makes perfect sense to me....
Would you rate compression stop valves equally than Sharkbite stop valves, or compression are better?

 

[SteveW]

I'd say for most uses that compression would be better. Has a very long track record of success. Less expensive too.

 

[Gary Swart]

When you are installing shut off valves that may need replacing in the future and/or where you would be working where pipes are very close to a wall, then compression valves are the ONLY way to go. If the valves are in open when heat would not be a problem, they take you pick. Either will work just fine. Compression valves do not require the pipe be absolutely dry whereas sweating requires there be zero water. Not a factor if this in new work, but could be a problem in the future.

 

[Jadnashua]

A Sharkbite fitting relies on an O-ring to make the seal. To keep that intact, the end of the pipe must be smooth without any burrs or sharp edges. And, the pipe must be nice and round without scratches or dings. Once installed, the thing holding it in place are stainless steel spikes. As a result, it doesn't take a huge amount of force to rotate the valve, but pulling it off is tough unless you use the release. Given the choice, a compression valve is probably still the best choice, with a soldered one next, then a push-on valve like the Sharkbite. The first only requires simple tools (a pair of wrenches), while soldering requires a torch, solder, flux, and something to clean up the parts prior to soldering and some skill.

Note, not all valves of any type are created equal...some are better than others. For the most part, you get what you pay for within a type.