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Leaking galvanized thread

Posted by kingwah (My Page) on
Tue, Oct 9, 12 at 9:25

Last night we discovered a leak in the dry walled ceiling of our basement. Luckily we caught it early. The leak is coming from the thread of what I suspect is our water supply line.
Question, with the entire ceiling being dry walled (house was flipped before we bought) are there any viable solutions to either temporarily or permanently repairing the leak without tearing out large sections of walls and/or pipe. I was thinking maybe hydraulic cement might work, or cutting out the bad section and then use the existing elbow. I would cut out about a six inch section and re-thread the long piece and putting a coupling in. My plumbing experience is rather limited to replacing faucets and a little PVC work, but since this is most likely a supply line and therefore pressurized, I am a bit leery of patches.
Any advice is welcome.


Follow-Up Postings:

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RE: Leaking galvanized thread

That galvanized stuff is a pain. Make sure not to put your finger on that little brown rust spot or you'll probably have another leak (seriously).

I've seen plumbers do something like this: cut the 1/2" pipe, back it out using two wrenches, install a male adaptor, transition to another material, and connect the other end with a compression union. That's if you have good luck and the elbow isn't corroded and beyond hope. You might want to call a plumber in for this job.

One is supposed to use dielectic unions when transitioning to copper, yet I often see work where that little detail is omitted.

Ok, we'll soon find out where I'm wrong. Stay tuned for more comments.


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RE: Leaking galvanized thread

I'm not joking here. If you're going to try to repair this yourself (And a dedicated DIY'er would) I strongly suggest you do so on weekday morning. That way if you need to call a plumber the charge wont be a an after hour rate.
If I were to bet I'd say that the pipe threaded into the 90o ell will twist and collapse and not come out. Old galvanized pipes especially small diameter have a tenacity not to come loose.

Good luck and post how you come out.


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RE: Leaking galvanized thread

Let's say that we have two considerations, one being the pipe and the other being the drywall ceiling. The pipe is the number one consideration and the ceiling is down on the list at number ten.
Fixing one problem with old galvanized piping insures that a problem will soon develop at another place. Replace the pipes, then replace the ceiling.


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RE: Leaking galvanized thread

That's a good way to look at it.

That being said, I did a similar galvanized repair in a finished basement ceiling 6 years ago and no other leaks have occurred since that time (knock on wood). But it's only a matter of time.


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RE: Leaking galvanized thread

It is no small wonder that the joint in question is leaking, the bigger question is how did it ever hold water pressure from the beginning?

If you look at that joint you can see five or six threads exposed,,,,,WRONG!!!!! When an NPT(National Pipe Taper) threaded joint is properly made up there should never be more than one full turn of thread remaining exposed. The key to running pipe with NPT threaded joints is if you can't get it tight enough with the wrenches your using, get bigger wrenches. For those of you who are trying to squeak by with 12" & 14" wrenches, forget it...for 1/2" copper pipe the minimum size wrenches you need are one 16" to steady the pipe or fitting and an 18" to rotate the opposite pipe or fitting, and keep a 24" handie just in case. Personally, I would use a 24" & a 36" wrench.

When tightening an NPT fitting you have to be very careful to stop at the correct alignment. Never reverse a pipe, If you happen to turn past the alignment, even a slight bit you have two choices, either turn one more full turn and stop at the correct place or remove the fitting, clean the threads, apply dope again then make the joint up from scratch again.

We have to understand that GIP (Galvanized Iron Pipe) is actually BIP (black Iron Pipe)that has been given a coating of zinc on both the interior and exterior to prevent rusting however when we cut & thread the pipe the zinc coating is stripped away, leaving the iron pipe exposed and subject to rust. By applying a code approved dope and tightening the joint correctly the exposed portion of the pipe is contained in the joint were it will not be exposed to water & air which results in rusting.

When a joint is only partially tightened as in that joint there still remains sufficient clearance between the threads to permit water to enter by capillary action, and it will soon result in the threads rusting, leaving even a larger path for water until you have a leak.

I honestly wonder how they ever passed code inspection with joints like that.

But having said all of that, it doesn't negate the fact that the damage is already done and we are now left trying to figure out the best way to correct it.

The easiest solution would be to cut the pipe about 8" left of the elbow. Now unscrew the cut section of pipe out of the elbow and examine the interiour of the pipe. That pipe looks very good on the outside, but iron pipe tends to corrode or build up scale on the interior of the pipe, especially in areas where they have hard water.In a worst case the entire interior of the pipe is filled with a reddish sand looking material and there is no way to tell what the condition is until you remove a section. You an expect to find some scale & corrosion, but if the interior opening of the pipe is at least 3/4 the diameter of the original pipe you should be fine by just repairing this section.

Many would attempt to reuse that elbow but keep in mind that the rusting occured in the treaded section of that elbow as well. Odds are, there is rust clinging to those threads that would interfere with properly tighting the joint. Furthermore, that elbow was also not properly tightened.

I would strongly suggest you remove and discard that elbow.

Now lets move on to reconnecting everything. Begin by threading the pipe. To do so you will need a 36" pipe wrench to steady the pipe while you thread the end with a hand threading die. (both of those tools can be rented at any tool rental agency..I would expect to pay about $20 a day for the tool rental) If you don't know how to use the pipe threader ask the clerk at the tool rental to demonstrate it, it is really easy to learn. You will also need a pint of cutting oil to lube the pipe theading dies and usually they will supply the oil with the tools.

Now examine the elbow you are removing. Not that it has a male thread on the input end and a female thread on the output end. That type of elbow is properly called a "90 degree Street Ebow".

Next you will need a galvanized union to make the final connection. Attach the union to the pipe, then get a galvinized pipe nipple long enough to reach from the elbow to the union.

Make sure you apply dope to the male threads before making up a fitting. (do not apply dope to the female thread).

When tightening the joints make sure you use two pipe wrenches, one to hold the fixed side steady while you rotate the opposite part with the second wrench.

DO NOT APPLY DOPE TO THE FACE OF THE UNION. Unions have a soft brass face and they seal by pressing into each other. Applying dope on that face will interfere with the intended sealing system.


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RE: Leaking galvanized thread

Lazypup,

Thanks for that detailed and thorough answer. I wish you were in the Chicago area so I could hire you to do the job.
Last night I tried to use some JB Water Weld, but since it must be a hairline crack in the thread it didn�t work.
If I had the tools and a weekday free (as Confire suggested) I would be inclined to try it myself. I plan on having a couple of plumbers give me estimates, but I would lay odds that they will suggest I re-pipe the entire house in copper. I have tackled many projects about my house, but draw a bit of a line when it comes to plumbing and electrical as both can have very serious consequences if not done properly. I have been doing research and most everything I have read says that GIP has a life of 50 years at the high end. I suspect that most of the plumbing in my house is going on 71. The house was flipped before we bought it and they did use copper pipe coming off the water heater, but the skills they displayed leave a lot to be desired and now I wonder if they even made the transition from copper to the GIP correctly (Hidden by the ceiling). I am not sure when the connection in the photo was made. Some teeth marks in the elbow seem to suggest that it wasn�t an original connection, but it has to have been done more than the seven years since the house was flipped. The totally dry walled walls and ceilings in the basement should have been a red flag as to what they were hiding, but live and learn. Plus it has given me some good practice in my DIY skills.


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