[Texas, NW Austin area; the house is a production home built in '87 on a monolithic slab on grade]

Our bill has nearly doubled in the last 2 months; the first month we passed it off to other circumstances that we thought might have caused it, but this last bill should not have been so high...

(reference the attached drawing as a visual aid)
I checked the meter with everything turned off in the house, and the triangle was turning pretty fast. I don't have a shut off at the house though, only on my side of the meter. I thought I knew where the service line entered the house; there are (2) 3/4" PVC pipes that come out of the ground on the right side of the garage (relative to the street view) and enter the wall. There is a water softener on the opposite side of the wall, and the water heater is in a closet open to the garage, on the wall common to the house. There is a hose bib on the left (north) side of the house coming out of the wall, but that is all.

The past few weeks have been very dry, and I don't have much grass under my big trees in the front, so it should show very obviously... I couldn't find any signs of water in any logical path between the south garage corner and the meter, which is on the opposite lot corner, across the driveway... however, while I was looking, my neighbor came out, and after telling him my problem, he said he noticed that the ground next to his house, which is a couple of feet down a short hill from mine was really soggy and lush. We walked over and I could push my heal a few inches into the ground. The soft area was almost the full length of his house, along the low area; you could feel the ground compress below your feet while walking. We dug a hole and it collected water almost immediately. However, this area is nowhere near the expected/logical path of the service line...

It was getting late, so I turned the water off at the meter and went to bed. I went out to turn the water back on this morning and the water had drained from the hole; within minutes of turning it back on, the hole collected water again... this is definitely coming from my service line...

I dug another hole east of the first one, and it collected water, another east of it, and it did not collect... I went back and dug one west of the first; it collected water, so I dug another west, and it did not. I dug 3 more holes uphill, centered on the middle hole of the first row, and the one in the middle collected water within an hour...

I'm relatively certain I have found the general area of the leak, but not sure where to put my efforts; the big juniper trees would have been there when the house was built in '87, so it doesn't seem logical that they would have run the line through the clump of trees, but the outermost tree is up the hill and on on my property line... is it possible that they ran the line onto my neighbors lower property, around the trees and rocks, and back up and over to the north corner of my house, entering the slab below grade?

 

If it was a metal water line it could be found/traced with a metal detector.

 

I often don't bother trying to locate the leak. They can be difficult to find and sometimes one leak just means the line is corroding through and more leaks are immanent. So, I just replace the line. Start at either end where you know where the new line must connect and dig to the other end. The location of the old water line doesn't matter.

As for your site I would have run the line arcing up through the front yard. You never run a water line on someone elses property and you usually stay away from the property line and you avoid trees. During construction it would have been simple to just shoot straight from the meter to the house. Remember you have to think of how things were during construction 30 years ago; no grass in the yard, no driveway, no landscaping... Often the easiest way is how it was done.

 

I was told by a friend of my dad's that is a plumber in Houston (I used to work for him as a teenager) that it is most likely 3/4" PVC. I'm going to dig up the line near the meter and see what's there.

Part of the problem with replacing the whole line is that I can't tell where it enters the house; I thought it would have been the garage where the (2) 3/4" PVC pipes come out of the ground and enter the wall at the WS, but the leak isn't anywhere near that would-be path. The other problem is that, if it is at the NW corner of the house, I don't have a straight shot; I'd have to go under a bunch of large (4-6") roots from my neighbors ash trees, then through the clump of large junipers that take up the space between the driveway and property line (which wouldn't be possible without removing them), or go around them on my neighbor's property. I think a repair would be much more practical... at least temporarily until we can afford the time and money to replace.

That was what I would have expected, but I can't see how it would be leaking where it is if it went to the garage. The juniper trees next to the driveway predate the house; the largest could be anywhere from 60-150 years old, so the only way to avoid them would have been to go under the drive, or just outside the property line. The saturated ground is on his property. These are production homes though and my house was built a few years before his; I used to work for a production builder (drafter/designer) and you never know what those trades will do just to knock out the job. I would also point out that his meter/shutoff are adjacent to each other, so they are right on the line...

So, I guess my next question would be, would they have entered the slab below grade, then up into the wall at the NW corner? Doesn't seem likely... Or maybe... ran under the driveway or the flower bed between the driveway and the house, under the garage floor, then into the wall at the WH?

 

Has the soggy area in your drawing always been there or is it new?

Yes, your water line would enter the house under the slab. This is done wherever there is a chance of freezing. If you can, follow the plumbing in the house and hopefully find where the water enters. I would start by looking around the water heater.

Stop thinking about the driveway and it's impact on the water line. The driveway was likely installed after the water line. During construction they likely trenched a line between the meter and house. If there was a pile of bricks in the yard they diverted around it. The key is to remember what it was like during construction. Just a open dirt area with maybe a bit of gravel for a temporary construction driveway.

For legal reasons it is extremely rare that they routed the water line off the property. They were trenching with machinery so some tree roots isn't a huge impediment though you try to avoid them.

Water will take the path of least resistance. If the leak is under the driveway the pavement and compacted soil can mean the water travels horizontally until it finds permeable soil and a way to the surface.

 

I've never noticed that area to be soggy, but it does collect rain runoff and maybe water from using the hose bib on that side.

So I figured part of it out; there's a part of my driveway with a 12" strip at an expansion joint... I dug about 6" down next to the N side of the driveway at that strip and found (2) 3/4" PVC pipes... I followed them out to find that they turned down to the main line; what happened was that the WS was added, so they cut the main line, ran the loop under the driveway, to the garage, back under the driveway, then rejoined to the main line. So, that mystery is solved and I can rule out entry at the SW garage corner, as it's just a loop.

I followed the main line (PVC) a couple feet from the loop and the trajectory seems to point at the trees. I think they ran it through the trees, then turned across the front of the house under the flower bed, into the garage at the WH. The ceiling in the front and north sides of the house slope 3' with the rafters, and there aren't any lines above the flat ceiling, so it isn't run through the attic.

Now to decide where to start the digging efforts...

 

If you were sure it's the outside water line, I'd agree with Pilot Dane and probably just re-trench and run a new PE (black plastic pipe) line. Since it's not bubbling up anywhere near where the line likely is, you're really guessing at both the pipe location and the location of the leak. The water is most likely moving underground before it's getting to that wet spot.

If you want, you can start digging at the meter and follow the pipe, dig a hole every 2-3 feet, find the pipe, and keep going.

I would probably consider cutting the pipe where it comes up at the garage. First confirm that it's actually your main coming in there, then add a shutoff. The shutoff at the house will be important to ensure that the main line is actually leaking, and not a pipe under the slab. I'd hate to replace the whole piping from the meter to the house, just to find out that it was an under-slab leak!

 

Sorry I disappeared for a day, I had to become a plumber in addition to my normal responsibilities...

So my findings and theory in my last post were correct; the pipes at the garage are just a "new" (20+ year-old) loop for the added water softener, and the main line runs up through the trees along the driveway then turns under the flower bed (see updated drawing). I dug down where I expected the corner to be, and a couple feet down hit burbling mud... the elbow was split. I put in a new section for the elbow, and all is good!

 

Wow..... all that extra digging and piping to put the softener on the opposite side of the garage.

Good job.

 

Yea, but it's really the only place to put the WS; the garage entrance is on the north side of the garage. With that said, it has been unplugged since we moved here 15 years ago, so I might just reconnect the original service line and bypass the WS loop.

 

I would have never believed that much extra underground piping. Glad you found it!

Print out your picture and put it in a drawer with your appliance manuals and such... a future owner might need it!