I was cleaning the crawlspace under the house and discovered two 3/4 inch white PVC pipes that run across the crawlspace buried under ground (4-8 inch deep) and terminate at the perimeter foundation footing.

One of the pipes has a T-connection in the middle facing upwards, the top end is not capped and is filled with dirt.

I wonder if this was done on purpose (for some kind of drainage or something) or this is a part of abandoned yard irrigation system left by when they build a house addition

Does anybody know any method that would require such PVC pipes underground in the crawslapce?

Pipe: enter image description here

T-connection: enter image description here

Pipe ends at foundation footer (next to the pipe is a big root that goes under foundation as it seems) enter image description here


1 Answer 1


Since its under an addition I think your guess about being part of an irrigation system that was abandoned is the most probable.

  • I've never seen residential irrigation systems with pipes that large and why would there be two? Hot-Cold? Send-Return? Commented Dec 23, 2018 at 17:21
  • 1
    @SteveWellens 3/4" PVC is very common for irrigation in Texas, and the two pipes would likely serve 2 different zones. Zone controllers are typically buried in groups, so you'd see multiple pipes leading out from a common location to each of the zones served.
    – mmathis
    Commented Dec 23, 2018 at 20:43
  • I use 3/4 for main lines to the valves and if a larger zone to reduce pressure drop so this is not uncommon at all.
    – Ed Beal
    Commented Dec 23, 2018 at 20:46
  • If it was for irrigation water supply, wouldn't one 1 1/2 " pipe be more reasonable? (Rather than running 2 3/4" pipes). I've seen people run pipes for future cables (AC Power, network, CATV). There would be two pipes because you don't want AC next to your network cable in the same pipe. Commented Dec 24, 2018 at 4:52
  • 1
    Multiple zones are run all the time using 1/2 " pipe limits the number of sprinklers, my last home had 6 zones but because of the size I could only run 2 at a time and that was with 3/4" if I had used 1/2" I would have needed at least 3 more zones (more output modules and valves) to do the same job so 3/4 " was actually cheaper.
    – Ed Beal
    Commented Dec 24, 2018 at 17:49

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