Test/repair leaking irrigation line under concrete patio


Old 05-08-16, 01:33 PM
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Test/repair leaking irrigation line under concrete patio

I have a small amount of clear water (less than 1/4 to 1/2 cup) coming up through my attached garage concrete slab every few days over the past 6 weeks. To my knowledge, I there are no water pipes or drains under the slab. I suspect the source of the water may be coming from a broken irrigationl line to my sprinklers, that is under my concrete patio. I had new concrete patio installed about one year ago, but (unfortunately) I neglected to have the existing irrigation line replaced, missing the perfect opportunity to do so (my bad).

The water line in question exits my kitchen wall and goes down through the concrete patio to a "T", that goes left and right to sprinklers. Note that prior to installing the new patio, the water pipe (PVC, I think) going down was through a dirt square area, which is now completely covered by concrete. The water line in question goes approximately 35 feet (17 feet, then steps down, and another 17 feet) to a garden area where my sprinkler on/off valve is located. Since the area in my garage where the water is wicking through is 6 feet from my out side wall, which lines up with the garden area, I'm guessing that the area where the water line is broken to be approximatley the same distance under the concret patio. In the past, while doing some sprinkler repairs, I noticed that the water line exiting from under the prior concrete slab was either a dark gray color or black (I forget) and was somewhat brittle. I was able to do the sprinkler repairs using 3/4 inch PVC pipe.

1.) Is there a way I can test the water line under the patio to definitively identify it as the source of the water in my garage?

2.) Assuming that it is however, can I possibly stop its leaking by trying to run a smaller, (say 1/2 inch) flexible PVC pipe or black poly pipe, inside the 3/4 inch gray/black pipe (in my garden area where sprinkler is located?
3.) If it is doable, are there any downside issues to be aware of?
4. If not doable or advisable is there any professional services that can fix the broken leaking pipe, without tearing up my new patio? (Note: all such trenchless services I have been able to find online (called CIPP or pipe bursting) seem to be for sewer or drain pipes and look expensive (one website estimated $60 to $800 per foot???)
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Old 05-08-16, 03:22 PM
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Welcome to the forums.

You'd need to dig up the line where it leaves the patio to cap it and put in a pressure gauge to monitor for a leak.

1/2" poly won't fit inside of 3/4" poly.
1/2" poly won't fit inside of 3/4" PVC either which is what you've described as hard and gray.

A normal sprinkler system has a large water supply line that feeds multiple valves and then the sprinkler zones. Do you just have a home brew one zone set up ?

It sounds like you may need to refeed the sprinkler line from an alternate location. Can you abandon that feed now in the concrete and then come out of the house at the end of the patio ?
Old 05-08-16, 04:42 PM
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Thanks for replying

This may be a "home brewed" setup, not sure as it was already installed when I bought the house in 1988. There are only 2 on/off manual valves, 1 on each side of backyard, connected via "T" from water source. From all I know the sprinkler water pipes, under the patio, could have been installed in 1968, when house was built. When I worked on the sprinkler years ago, I connected new 3/4 inch pvc pipe to the old dark gray/black pipe with a pvc coupler fitting, with no problems.

Questions: to your knowledge would a 1/2 inch flexible pvc pipe fit into the old pipe or perhaps I should just dig it up, cut off section and measure the inside radius? Maybe I can find some other type of tubing that would fit?

Thanks again
Old 05-08-16, 04:47 PM
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I have no other water source in backyard. Existing source uses same water source as kitchen faucet (I think) because it pipe exits through outside wall right at location of kitchen sink. Entire backyard concrete patio goes from one end of house to the other. Only other outside water source is in front of house, where sprinklers were also installed, but we're all torn up during pool installation in 1989. Front yard sprinklers were connected where main water feed enters house from street water meter.
Old 05-08-16, 04:59 PM
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I know of nothing that will go inside your pipe. You will have to go around patio and abandon tour lines under it. Sorry no easy fixes for your problem.
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