Water leak at connector?

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Sep 6, 2011
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san francisco, CA
Three weeks ago I went out to the house to make more repairs. I checked the water for hardness and found it was hard. I regenerated the water softener manually and made a few minor repairs while I waited for the cycle to end. Two hours later the cycle was over so I decided to test the water right at the softener. I shut off the water to the house, relieved the pressure and started to unscrew one end of the corrugated copper flex line. Water sprayed out of the flex line. I removed the flex line and saw a break in the copper. I didn't have the time to go to Home Depot and buy a new flex line so I left the water shut off and went home. The house is vacant so there is no impact.

I bought a new corrugated copper flex line and went out to the house the very next week. I installed the new line and opened the water supply ball valve a fraction. I saw water spraying from a nut at the fitting so I tightened it until the water stopped. I turned on the water all the way and checked for leaks. I saw none. The new flex line was bone dry. It only took a few minutes to install the new flex line. I made additional minor repairs and left 3 hours later. I made a final inspection of the water softener and everything was still bone dry. Not a leak in sight.

Three days later my sister called me and said my brother in law went out to the house to bring out the carts and saw water spraying out of the nut I had tightened. He said he tightened the nut and stopped the leak. My question is how is this possible? There was no leak for three hours while I was there. The only thing I can think of is that my brother in law moved the new flex line and created a leak.

Here is a picture of the old, original corrugated copper flex line installed 20 years ago by the water softener contractor.


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Nov 14, 2017
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Lafayette, CA
They are purely rubber washers for the seal. Teflon and paste = completely un-necessary.
Copper flex is not the product of choice any longer.
Corrugated stainless steel rules, has better/easier flex and less resistance to alignment issues.
There could be transient pressure spikes.
p.s. I've never seen a water softener in the S.F bay area in my entire 48 year career.

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