plumbing: how tight should you have to crank a union

I got a union to help connect up a whole house filter since the filter has threaded inlets and it had some elbows nearby. I figured this would make it possible to remove stuff later since I could unscrew things without cutting all the pipe. The thing is, this stinking union will not stop leaking at the compression spot. I've cranked it down almost to the limits of what I'm capable of doing. Is this right? Is it normal to crank the snot out of these things, or do I have a faulty union or something?
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My heating and AC boss used to dose unions with WD-40 or equivilant. So the threads would slip instead of tighten and jam up.
Plumber friend of mine used to dose the threads and mating surface with Rectorseal #5 for sealing effect.
One of t hose two should do it.
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I had the same problem with a union on a steam heating system. After posting here, someone suggested Rectorseal #5 and I bought it and used it. That solved the problem. It did seem to help lubricate it a little as I tightened it, and it definitely made the seal.
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Chuck wrote:

If it's one of them CheapChinese fittings it's probably the fitting -- I've had nothing but trouble w/ 'em.
If the imperfections are small enough a layer of permatex or similar may be enough; some of the ones I've had have large enough pitting or other defects to be clearly visible--there's no hope w/ them.
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I have polished the mating surfaces with fine steel wool then wiped some pipe dope over the area before tightinging them up. Since I started doing this I have had no leakers.
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I went up to my cabin and turned on the water only to find bursts in two places. Went to Home Depot, and bought something called Shark Bite, IIRC. It worked. I had to put one compression 90 ball valve in as it was less than half a Shark Bite 90 valve. We'll see. But the stuff was incredibly easy to work with.
Steve
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Metal or PVC ? Is there a slot machined in there for an "O" ring ?
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Rudy wrote:

Metal. Looks like brass with a copper pipe.
Interesting about the lubrication. I had pipe dope on it the first time, from sweating the pipe, and I removed it the second try. I've torqued the heck out of it now and it _might_ be sealed. I'll wait overnight to know for sure. If it's still leaking I'll try some WD-40 and/or permatex. Thanks.
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Most plumbers don't use pipe dope for sweat solder fittings. They use flux.
I wouldn't use WD and permatex at the same time, they might not be friends. A dose of Permatex #2 non hardening (the black messy crap) may do the job. washes off with alcohol "drygas" when you get it on you. DAMHIKT.
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Chuck wrote:

A normal union doesn't need permatex, wd40 or anything else. If the mating faces are clean and you have good alignment and it leaks after nominal tightening the union is defective.
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Maybe, but I've been fighting them tight way before the cheap imports hit these shores., Once I saw the guy changing my deep well pump smear a little pipe dope on before attempting to assemble the ones in the well head, I felt silly. I now follow his lead, and have little trouble with those.
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Sounds as though anything 'slippery' helps lubricate the threads so that the union will put smooth and tight compressive force on the metal to metal joint of the 'olive' and copper pipe etc.? Not that we are stuffing up the joint with some sort of sealing compound. Correct? Thinking about one part of the Middle East where 'plumbers' and repairers tended to put sealing tape on anything with a thread, even if not required. The threads, in some cases, were really clogged up with sealing tape debris in some cases which made tightening a chore!
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Mostly, but the well guy put a smear on the mating surfaces too. There is a little friction there as it mates, and that makes it go together easily. I no longer get the 36" pipe wrench out when dealing with a union, but I used to.
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