Are pipe unions directional?

A flare fitting can hold a substantial amount of pressure, whereas a compression fitting may eventually start to leak over time. The ferrule in a compression fitting doesn't seal as securely to the tubing as a flare fitting, leading to potential loosening and eventual leaking.

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In compliance with current codes, brass fittings are generally required. The gas line riser must use an approved AGA (American Gas Association) listed flex line for gas, and the manual gas ball valve should have an AGA rating as well. Copper tubing hasn't been permitted for many years.

Around 1990 or so, galvanized pipe was also approved for gas use. This change was due to advancements in the galvanizing process to prevent flakes from coming off the pipe.

T_Bone

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Dan's Question:
What is the correct way to install a galvanized union? Do you pull it apart and install each side to the pipes, then tighten the union together? Should Teflon tape or a pipe dope be used on the threads? If installed vertically, does it matter which side is up? Thanks!

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Response from e-plumber (NY):
The union nut should be the last part to be tightened after the end pieces are secured to the pipes. You should hold back on one half of the union while tightening the larger nut, and applying some thread compound to the mating surfaces and threads can help. This makes it easier to assemble without binding. The orientation—vertical or horizontal—does not matter.

Repair your leaking plumbing fixtures ASAP. This slow drip can waste over 7 gallons of water per day.

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Post Reply

Response from packy (MA):
I usually hand-tighten each end and then hand-tighten the big nut to hold things together. This makes it easier to wrench-tighten the ends. I don't use Teflon tape on the union threads but apply a little grease behind the big nut and on the union threads to make it turn easier. On a vertical pipe, the nut goes on the top piece to prevent it from sliding down the pipe during assembly or disassembly.

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Response from dlh (TX):
I like to place the union on the side least likely to be disassembled. This way, I don't have to worry about forgetting to install the nut when reassembling.

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Response from hj (AZ):
You can only install it one way. No sealant is required on the mating surfaces, although some joint compound can make it easier to tighten. There is no preferred direction, but it's wise to place the outer ring on the upper section so it doesn't drop down the pipe and out of reach.

Post Reply

Response from hj (AZ):
If it's up against a wall or in a corner, I position it in the easiest way to tighten it. Let whoever disassembles it later worry about how to access it.

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