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I'm working with 3/4" brass fittings, which seem pretty robust.

Some plumbing fittings should be only finger-tight. My friend said I should use 2 wrenches to make these as tight as I can, and then some.

How tight should I make them?

EDIT: I am plumbing water, but I'd like to learn to plumb gas, too.

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There is a scientific term: nudge and a grunt tight! – shirlock homes Mar 3 '12 at 11:06
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Brass threads are softer than other metals, so they seal well. You won't have to get it as tight as steel fittings for example, but you'll want it tighter than hand tight. Is this for gas, or water? – Tester101♦ Mar 3 '12 at 14:14
This is for water. Edited. – Jay Bazuzi Mar 3 '12 at 19:25
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put a few winds of telfon on the threads and snug them up. Don't go crazy, but use two wrenches and refer to snug and a grunt rule! – shirlock homes Mar 4 '12 at 12:14
There have been four mentions of the "snug and grunt rule" but nobody has said what the rule is. – ArgentoSapiens Oct 18 '12 at 12:53

3 Answers

up vote 2 down vote

If using Male and female fitting a seal will be needed eg. teflon tape and firm is sufficent because if you're just jaming the brass together you can break the seal provided by the teflon or similar, if using unions they seal brass to brass and use the above mention nudge and grunt rule, just be carful not to mishape the fitting as brass can crack or bend with undue force.

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The Teflon tape doesn't create the seal. It reduces friction so you can tighten more with the same turning force. The threads deform each other to make the seal. – Jay Bazuzi Apr 18 '12 at 15:38
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"just be carful" is not very usful advice: you don't know how much force would be too much until it's too late, right? – Jay Bazuzi Apr 18 '12 at 15:40
If Teflon tape doesn't create a seal and is just used for a lubricant as you sugguest why does it come in different thickness? And that would mean that you are using tapered thread brass fitting not parrrell thread, because if you are trying to just bind the threads together they won't only the end of the male fitting touching the inside of the female fitting would and parrrell threads arn't made for that sort of use, unions are. – UNECS Apr 18 '12 at 18:17
As for just be careful, I'm sorry I wasn't clearer, you want to apply sufficent Teflon tape so as the fitting becames very firm before the brass MI and FI fitting bind, when I said be carful I was implying not to use your 3 foot long wrenchs and start going to town. – UNECS Apr 18 '12 at 18:20
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Just be careful should be applied to reading Wikipedia as well. – UNECS Apr 18 '12 at 18:32
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up vote 0 down vote

I assume that you are referring to National Pipe Thread fittings. Unfortunately there is no real one answer to the question of how tight should I tighten them as there is may differences between materials and the quality of the threads. This really becomes a "tighten until it just feels right" type of answer and that comes with experience. In general terms you want to aim for 2 to 3 full turns after hand tight. If it still feels loose, complete another full turn. A lot of plumbers will use both teflon tape and pipe dope. Depending on the thickness of the teflon tape you will want to use 3 to 6 wraps in the direction on the threads.

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"comes with experience" - Did you do negative testing, where you tighten less than your hypothesis, and get a leak? – Jay Bazuzi Oct 20 '12 at 5:30
No, I did not do any negative testing. I was taught this method throughout my apprenticeship. I have had leaks were I was not 100% confident on a joint and you lean from them. When you're plumbing you can't afford to have leaks as they are time consuming to repair. – pdd Oct 22 '12 at 15:25
up vote -1 down vote

I'd like to suggest that you try the snug and a grunt rule. Use two wrenches so that you will have the right force to insert and still will not deform the fitting.

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What is this "snug and a grunt rule" you speak of? – Niall C. Oct 18 '12 at 14:07

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