Water heater pipe leaks prematurely

[thezman]

I have an interesting problem. I moved into a 5 year old house on 11/01/2008. On 12/25/2008 (yes, Christmas day) the pipe that connects the hot water side of the heater to the pipe going into the house leaked. It was a flexible copper pipe. It leaked at the joint on the wall side (not the heater side). The leak was small, one drop at a time. I replaced the pipe with an identical one.

Some 15 months later same pipe leaked again at the same spot. I replaced it again thinking I will do some research about the premature leak later but I never did.

Now another 15 months later the pipe leaked again at the same spot. So I have replaced it again but want to find out why the pipe only lasts 15 months. The cold side pipe is still the same that was there when we moved in. Any advise is appreciated.

At my old house the water heater was replaced in 1997 and it worked w/o any problems for 13 years.

Thnak you.

 

[Mr_David]

When you install it do you put anything like teflon tape or paste on the fitting you attach the supply to? DON'T

Check the end of the fitting. It could be deformed or defective

 

[thezman]

I used teflon tape the first time I replaced the pipe. but I have not used any thing the last two times. The fitting looks fine.

Thanks.

 

[Mr_David]

It's a mystery. I'd change out the fitting.

 

[Another-Plumber]

i find the insulation foam always causes leaks, if you are using that, get rid of it

 

[Beni]

Check the connection at the wall, is it a tapered NPT pipe thread or is it a straight thread. Its possible someone installed a NPS - Straight fitting. It sort of fits but its not compatable. You'll want a NPT threaded fitting.

 

[thezman]

Mr_David,
You said don't use teflon tape or paste but i thought those things help to slow the corrosion when two dissimilar metals are connected? What's the drawback of using them?

Another Plumber and Denis1982,
It has foam wraped around it and so does the the other (cold) side which has never leaked. But I will take the foam off.

Beni,
The connection at the wall is a tapered NPT thread.

Thank you.

 

[LiQuId]

on a npt thread it is the 30 degree taper that actually seals the joing, teflon tape does a little to help if there are inperfections in the thread but both it and dope are actually considered lubricants as they are not solely responsiblle for the seal but in its assisatance.

if the 2 metals are too far apart in nobility then electrolysis will happen regardless and leaks will eventually happen.

 

[Mr_David]

The neoprene gasket inside the union of the flex supply is what makes the seal, Not the threads.
The only thing the tape does is maybe lubricate the fitting for easier tightening, but really not necessary.
How's the temperature of the water.
The hot side tends to expand and contract more when hot water was is drawn from the heater.
That is probably why the cold is not effected.

Some unions on copper WH flexes have an insulating sleeve for dielectric isolation.
The ones I use currently do not, but are accepted by local code here as meeting the dielectric requirements.

 

[AllAces777]

You can always put a coupling on the nipple, and a new nipple connecting the water flex and coupling. I would have to say there is some imperfection on the nipple or threads of the nipple. The expansion and contraction of the pipe due to the hot water is accentuating the imperfection and the rubber gasket is not enough to hold it. A new coupling there will probably last a lot better.