I have a Compression Union, which connects two pieces of pipes. One joint leaked, because nut loosed. I unscrewed the loosed nut, applied “pipe thread sealant”, then tightened the nut very tightly. The leak stopped about half an hour. Then leakage started again and water came out from the nut, although the leakage was much slower than before.

Any idea of how to fix this problem? Why the new leakage did not start immediately after I tightened the nut?

Thanks a lot.

KeepItSimpleStupid

Inspect the union very carefully for a hairline thread crack.

Pipe thread sealer should not be used on compression fittings. The sealing surface is not on the threads.

zjclucky

Thank you very much.

Will the Compression Ring crack if I tighten the Compression nut too tightly?

Can the crack of Compression ring cause the leakage?

Flying Blue Eagle

Zjclucky - Yes if you tighten it to far, you can also be putting a small kink in the pipe is why you are not getting a good seal . You did not say ( WHAT KIND OF PIPE YOU ARE WORKING WITH????????) .That would help us alot to know, If its copper and is not real stright where you are putting the compression fitting then that could be the causeand you could have tightened the fitting so tight that it cracked the copper pipe . SO TELL US WHAT KIND OF PIPE YOU ARE WORKING WITH ?????? GOOD Luck & GOD BLESS .::: Hello Kiss

zjclucky

Thank you very much. Yes, it is copper pipe and not straight.

But if I had cracked the pipe, a lot of water should have rushed out right away. Actually now the leakage is very slow.

What really confused me is that after I tightened the nut following the first big leakage, the leakage STOPPED FOR ABOUT HALF AN HOUR before it started again, although the second leakage was much slower than before. Why the second slow leakage did not happen immediately after I tightened the nut?

KeepItSimpleStupid

Not necessarily true. Had one suddenly gush water about a month later. It's called stress.
Water flow and temperature changes cause minute movements.

How big is the pipe?

Compression fitting - Wikipedia, the free encyclopedia

Compression Fittings

zjclucky

Thank you very much.

1/2" inch copper pipe.

KeepItSimpleStupid

Actually, the "copper pipe" used in the home is really "copper tubing" and I purposely used your terms. It comes in K, L or M grades which is the wall thickness and intended use.

The outside diameter of pipe and tubing are very different. It's somewhat complex. It's Schedule rating determines the wall thickness. Schedule 40 is the most common.

It's very important to get compression right the first time. Square (both the end of the tubing and the intended final position), burr free, clean and fitted tightly in the fitting before tightening the nut. Don't overtighten.

zjclucky

Thank you very mcuh.

speedball1

To form, a perfect fit the pipes should be in line with oneanother. If they are cocked the connection won't be completely together leaving a small gap. Line the two pieces up and try again. good luck, Tom