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 Acceptable play in black pipe connections?
Author: rcm4 (CA)

I appreciate the opportunity to learn from / add to this forum. Wish all a Happy New Year.

I'd be grateful for your input on the job I just completed. Due to it's inconvenient location penetrating about 10" up through a washroom floor, I relocated a 1/2" gas line (water heater shut-off valve) below the floor, through the the bottom plate and in between two wall joists making a 90 rt hand turn for 5" then 90 straight up 24" with another 90 penetrating out through the (soon to be) drywall. All in all, 6 fittings not counting the 24" riser. It involved joining 3 varying sized nipples and 3-90"s to make the run next to the wall joist I'll use as a support.

While I would have preferred having all the fittings dead tight, that wasn't possible and still maintain the necessary alignment to reach the desired destination and doing so imho, would have caused them to be over-tightened by a full turn. AS it stands, due to my not having them all dead tight there is some play in the fittings. In other words, the 24" riser is not rigid, but rather can without much effort rotate the the attached piping run up and down. All the male fittings are in 5 threads deep with about 4 threads visible. I assembled all the new connections using Rectorseal #5. I'll secure the works with clamps/ pipe straps once I'm satisfied all is safe.

I did the bubble test and all checks out with no sign/smell of gas.

Should this ability to rock the fittings some, concern me?

Thank you

Edited 2 times.

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 Re: Acceptable play in black pipe connections?
Author: bernabeu (SC)

Proper tightening would be 7, repeat 7, turns total to match the 7 threads in the fittings.

All NPT tapped fittings 1/8" - 2" have 7 threads.



"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

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 Re: Acceptable play in black pipe connections?
Author: packy (MA)

i disagree with my friend from SC.

given that the nipples and the fittings are made off shore or below the border, no one can say the exact amount of turns each one must have. the good quality and consistency just isn't there.

one little plumbers trick... say you need a 6 inch nipple. so use a 3 inch, a 2 1/2 and a coupling. yeah its an extra joint but if it allows you get everything really tight and have your proper alignment then you are good to go.

BTW.. loose fittings are not acceptable

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 Re: Acceptable play in black pipe connections?
Author: bernabeu (SC)


The threads may or may not be exactly/properly machined


there are exactly 7 in a (f)NPT fitting sized 1/8" through 2"

which is the DESIGNED proper 'make-up'


particularly when piping flammable(s)

proper make-up = seven turns.

(albeit, if it 'feels' tight at 6 turns it is 'good to go)


never, ever, no way, no how, LOOSE FEELING with 'play' on a gas line

ps. if the fittings are NFG then they are NFG and should NOT be used - if the (m)NPS threads are NFG then they are NFG and should NOT be used


"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Edited 1 times.

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 Re: Acceptable play in black pipe connections?
Author: packy (MA)

bern... i think that is what i am saying.
or at least trying to say.

back in the old days we used wicking and pipe dope.
alas wicking is not allowed on gas but pressed "O" rings are ????

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