I have seen plumbers use all sorts of rituals for sealing threaded joints and am curious as to the best way to make reliable threaded potable water joints.
Those I've observed recently are:
A wrap with thin (white) teflon tape A wrap with thick (yellow...gas) teflon tape The teflon tape augmented with RectorSeal No. 5 The teflon tape augmented with RectorSeal T plus 2 Just RectorSeal No.5 Just RectorSeal T plus 2 Permatex (black gooey mess) Dry.
The pipes used have variously been threaded copper, brass, galvanized steel and sch 80 PVC.
All of these various methods have been employed by licensed plumbers. (And, some even leaked after a few days.)
Surely there is a consensus among those "in the know" as to what the best technique is. Please let me know what it is.
I use this on things I expect to take apart in the future.
Would be my choice, on gas lines, see above.
Harvey's pipe dope with PFTE (teflon), is the stuff I have available and use for things I don't expect to take apart.
The licensed plumbers used white teflon tape and pipe dope (don't know which brand), when asked why both?, a: "it is cheaper and easier than a return call".
Haven't seen that one. The only place I use tape is on the flex connection that couples the device to the permanent gas lines. I've had it go the other way, the use of pipe dope voids the warranty on my new Moen bathtub valve, supposedly due to incompatibility with the plastics. I used Harvey's plastic compatible (I checked the label) TPFE (teflon) dope, and so far so good.
That is what I meant by take apart in the future, when a new appliance is installed.
Other than replacing the water heater, I'll call a pro for the rest of the gas line work.
I do use teflon on temporary work, such as when I put the shower head and stuff on now, since it will have to come off to install the wall board. Once it is all together and done, then it is time for pipe dope.
Teflon tape is fine, but it has it's limitations. I carry a roll of it in my tool bag, but it hardly ever gets used.
Like I said before, if you use teflon tape on your gas joints, it may void any warranty on the downstream equipment. Bits of the tape may get in between the seat and the operator and may cause the valve to not close completely. The gas may dribble out, but you get enough gas and BOOM!
Teflon tape is for water connections only, in my opinion
If you use pipe dope, just make sure it is Rector Seal. I used another brand once; something in a tube and it said it never hardened . It was impossible to get the joint apart a couple of years later -- I had to use a hacksaw, and a hammer and cold chisel to take the fitting apart in pieces.
As a pipe fitter I install and tested threaded pipe everyday, so I guess I could say I am -in the know. The secret to making a reliable threaded connection is in the design of the threaded connection. The threads on the pipe and inside the fitting are a NPT (National Pipe Taper) thread. As you screw the pipe into the tapered fitting the force of the pipe going into a ever increasingly smaller fitting is what seals the pipe to the fitting, so having the correct taper on the pipe thread is essential to getting a reliable connection.
If the pipe and fitting are store bought you can be sure of the correct taper. If you have threaded the pipe yourself a good rule of thumb is to thread a scrap piece of pipe ( be sure to apply enough thread cutting oil when you cut the threads) and turn the fitting on dry by hand. You should be able to turn the pipe 3 to 3 ½ turns before it starts offering resistance.
I less than 3 to 3 ½ turns you have cut the threads to shallow and you should readjust the pipe dies (close the dies up a little). If more than 3 to 3 ½ turns you have cut the threads to deep so again you should adjust the dies to cut less. (open the dies up a little)
As far as the Teflon tape, RectorSeal and other compounds used,(commonly known as anti galling compounds, they are to prevent the threads on the pipe and the threads on the fitting from Galling (being welded together from the heat of friction generated when being forced together). They have little to do with getting a leak proof connection. Of course with out then you will never get a good connection.
As a Start-up crew member, my job is to hydrostatically test ( test with 150 lbs of water pressure for 24 hours) the screw pipe other crews have build, so I see and have to rework many leaky connection every day. The majority of the leaks I find are caused by not tighting the connection enough, although I do sometimes find one tightened to the point to where the fitting has been cracked and has to be replaced. As an apprentice I was always taught to tighten the connection until it will not go any more, then tighten it one more turn.
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