I have a copper pipe that I exposed when I cut open the slab to repair a nearby cast iron drain.

The copper line is old (since 1955) and it has a tee on it that was soldered on by the last owner in 2008.

This tee does not appear to be actively leaking. I don't see any mist or streams shooting or splashing out.

Yet every time I put my hand on the underside of this joint it is wet. I dried it with a rag and feel it again a d its dry. A few hours later it is wet again. Not wet wet just feeling moisture like a blade of grass in the morning.

I can't see the underside of the joint since its facing down.

Could this be condensation? But I don't feel moisture under the rest of the pipe.

Any suggestions on how I can definitively tell if this is due to a leak? Can a leak be so slow like "one drop of water an hour" slow?



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Condensation? No. "seeping leak"? Yes.

Check the water meter, look for that little spinning indicator they have on the dial, that tells you water is flowing thru the meter and in the water piping. You'd need to not have any water being used at the location while doing this. For a small leak the indicator may not spin fast but it will move over time.

I don't have the analog meter but electronic ones that allows the city to get readings by staying in their truck. I looked at the digital reading several times and it didn't change with no water usages. I don't think it will register. I am talking about enough water to moist the tip of one finger tip over several hours.

I would have thought the digital water meters would still have a way to indicate water flow even if it is small amount. That's an important function and has been on analog meters for years, would have thought it would be included on any later meters that came along.

You may need to assume it is leaking and redo that tee connection.



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I am not sure to what quantity it needs to change the reading.

If a faucet is dripping one drop of water an hour would the old analog meter spin at the moment one stares at it for say five minutes? I took the readings with a 1 hour time elapsed with no usage in between, same number.

You don't look at the water reading on the meter, you look at the little flow indicator. It spins even with a little water flow, will move positions in just a few minutes even with small flow. But if your leak is tiny tiny I suppose it would take longer to see any movement.

If as you indicated it is under a slab, there is a very good chance it could be a pin hole. Is it a hot water line? No matter, the age of your system indicates that it could be you have reached the useful life of your copper line, depending on soil chemistry and water chemistry. Try to verify with a mirror and flashlight that it is indeed a pinhole. Hot water lines are notorious for having pin holes. Also much of the copper back then was manufactured in China or Mexico using inferior methods of mixing alloys. Most codes today do not allow copper installed under a slab for the reasons mentioned. I had the same situation and had to run my new copper overhead in the attic. In fact today I have a friend that just had Upinor PEX installed in his home. It was expensive, over $7,000.00 for his 2 story, 2 bath home in Oceanside, CA. If you decide to do an installation see what your Plumber recommends is best for your area and then verify what he says with the city or water authority. I am partial to copper but your mileage may differ. Sad to say that years ago I installed copper under the slab in hundreds of homes because it was allowed by code. It has not been allowed in my area for 15 years or more. It has created a new industry for re-piping. One last thing. Does your homeowners policy cover leaks outside of the home or is this one inside the home? Most don't but some will under certain conditions. Speak to your personal Insurance Agent. All the best to you.



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PlumberLoren, thanks however the issue is not the actual pipe but a joint.

The last owner had inserted a copper tee into an existing line, and that tee appears to be leaking. So its the 2008 renovation that is leaking, not the original 1955 work. He should not have added a joint below grade anyway but what's done is done.

I have the slab cut open, but for another purpose so I don't have easy access to that joint which is located about 12-13" inside from the edge of the slab cut and therefore I cannot examine it up close. Cutting more of the slab is impossible due to I have already cut to the edge of the wall and the other side has kitchen cabinets and granite countertop and tiles with no spare pieces.



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Reading didn't change after 4 hours.

OK I was able to take a picture of the bottom of that tee.

Here is a picture showing both TEEs under the slab. Circled in red. The tee to the right is a 1/2" tee and that's the one that is leaking.



This is a close up showing the top of that really slowly leaking tee.



This is a pic of the bottom of the tee. Touching it I feel moisture, not a full drop of water just moist. Wiped it dry and 20 minutes later it's moist again.



A real close up. There is a lot of solder there, that seems to suggest the "plumber" had a real hard time getting the joint made?



The joint to it's left is NOT leaking, but was reduced from 3/4" to 1/2" then back to 3/4". At first I was puzzled why someone would do that...and use so many unnecessary fittings. He had a 3/4" coupling, then a fitting reducer to 1/2" to a piece of pipe then the 1/2" tee and all that fittings again.



Then it dawned on me perhaps when he cut the original soft copper pipe to insert the tee, he couldn't move the pipes enough to properly insert a tee and have the pipe bottom out into the fitting, so he ended up using so many fittings so he can gain some wiggle room and spread it out among all these fittings. Perhaps he only inserted 1/4" of pipe into the 1/2" tee that's leaking.



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These old soft copper pipes have a layer of white stuff over them, is that oxidation? If I sand them carefully will they take solder easy?

If the connection was brazed, the way it should have been, it may NOT have been done properly and the "solder" is somewhat porous so there is NOT "leak" as such, but rather a seepage through the brazing material.

solder on the "outside" of a joint does little to make a good seal for a bad joint.

It's a imperfect joint, they may have had trouble removing all the water and had some steam build-up. It really should be replaced.

Is there anyway to tell visually if it's brazed? I doubt it simply because the branches of these tees go to hard copper pipes with regular couplings and elbows. Why is there so much accumulation of metal at the bottom? Usually excess solder would run to the bottom and just drip off.

I am getting rid of these tees, but the best I can do is to replace them with straight couplings. The overall number of joints would be reduced to 1, but I can't totally get rid of all underground joints.

OK I made some progress this evening.

I took apart the old fittings. It was a real pain to work with my hands stretched out under the slab.



I cut the 1/2" line off, but heated up the 3/4" to remove the fittings to preserve as much pipe as possible.



I then formed a piece of 3/4" soft copper pipe from the cut position up to the manifold, did the same with the 1/2". I didn't solder them yet...I only fitted them together so far. Water is turned off. I will come back to solder them tomorrow night. I guess this is the best I can do although still have two soldered joints below (instead of 11 soldered joints previously). Let me know if you spot anything.







Look OK?

By the way, when I was taking apart the joint with a blow torch down below, the torch heated up the air and a cloud of hot air came up to my face. I think it will be a problem when I solder the joints. I wonder if a fan blowing at the trench will get rid of the hot air?

Your best bet is to get an air tank and blow out any water in the lines. Then do your soldering leaving the tubing open with a valve in the line. The valve could be a faucet or hose bib in the system to prevent steam from blowing out and cooling your solder joints. If you can't boil out any residue moisture, you cannot make a proper copper joint.

PlumberLoren, I have already put a wet vac on the pipes and extracted the water from them. I am not worried about that.

The "hot air" I mentioned is not the heated steam from inside the pipe, the hot air is formed from the surrounding air under the slab. When I turn on the blow torch it heats the air which rises up to the underside of the slab, then it goes sideway and exit out and that's where my face is in order to see what I am doing. You will get the same effect if you light up a blow torch 12" directly under your nose you will feel the really hot air rising.

OK I got the pipes soldered. It was a real pain to solder in that position with hands stretched and neck bent and not able to see what I am doing on the back side of the solder. I end up getting a small fan blowing in the trench to disperse the heated air from the blow torch and keeping my eyebrows.







I got rid of all the joints below grade except the two new couplings I put in. Not ideal but I can't think of anything better.

Next I will run two soft copper lines to the island in the adjoining apartment then tie the joints to the same manifold.

Looking much better! How did you keep all that heat from the torch off your face while soldering in there, did you wear the proper plumbing protective gear?





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I had a fan set inside the trench directing at the two joints. Last two days we have a bit of a cold front so temps were down into the 70s so that helped too.