I was digging a hole to plant a tree in front of my house last night (it was still light but the sun was down). The home is only a year old and is in California.

When I got a bit over a foot down, I came across a layer of rocks. Below the rocks, I hit something else.

I thought I might have hit the sewer line but when I look at it this morning, it just looks like clay pots - one inside another.

Reasons I am still concerned:

It may be some new funky pipe I never seen.

The rocks may have been an indicator.

The line/pots are perpendicular to the front of the house.

The line/pots line up with the closest bathroom.

Why would there be two pots (one in another) buried that deep?

Reasons why it's probably just pots:

The land was previously a large single home site with junk everywhere.

It looks a lot like a clay pot - about 8 or 10 inches wide.

Seems to be a really bad material for sewer line - I thought it would be PVC.

I thought the sewer would be deeper.

So can someone confirm that there isn't any kind on sewer or other line in or out of my home that looks like this? The piece in the upper right fits into the missing piece in the circle - I moved it to show there was more underneath.

I would have to dig up a lot more to get a better idea of what it is and am trying to avoid that.

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2 Answers 2


Only 1 ft down, I doubt it's a sewer line. Yes they were made of clay in bygone days, but were required to be deeper, 18-24" typically because they are required to be a minimum of 12" below the FROST depth, which in much of CA is 6" (unless you are somewhere like San Diego where it never freezes). The layer of rocks above it makes me think it was a French Drain system to avoid having standing water in the yard. That's done with plastic pipe now with a layer of gravel on top to facilitate drainage into the pipe and 1 ft. deep is not uncommon for a French Drain. But the fact that it is running perpendicular with the house, not parallel, is troublesome to it being a yard / gutter drain, unless it;'s the lateral that is taking the collected water out to the street or somewhere else.

I like the idea of flushing the toilet to see if you can watch flow, but if that fails, spray water on your roof and watch for the same thing; i.e. your downspouts might tie into this pipe (you should be able to see that at the end of the downspouts too).

  • Thanks for the info. Actually the clay is down about 18" - I hit the rocks a little below a foot and the clay was underneath the rock layer. It might be from some old structure that was on the property before the land was bought to make way for new homes. I thought it would have broke when the graded the land though. I dug past the white PVC yard drain - it was at about 6 inches. I didn't smell anything funky last night Jun 29, 2018 at 21:16
  • The rock layer wax guarding the pipe /helping it be a drain, my money is on french drain. Yhat will contain runoff. Jun 30, 2018 at 22:17

Clay has been used for a long time for sewer pipes - and for transporting water in general (google "clay sewer pipe California"). It could also be a drain tile installation - like a french drain. The simplest way to tell would be by having someone flush the toilet, or take a shower (something that will generate flow in the sewer) and look inside the pipe to see if there is more flow. You could also call 811 (Digsafe) or look up building records with your local town hall to see where the sewer line is on your property.

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    Clay sewer pipe pics: duckduckgo.com/… Proceed carefully. Jun 29, 2018 at 0:57
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    That actually looks a lot like what I hit - especially since I cleaned out a little more around there. On the other hand, my neighbor, who says he was a contractor, says there's no way they would spend extra time and money on clay when they could just use PVC - which also makes sense. I think it's old construction - I haven't seen any signs of water after a couple of days. I'm going to slide a paper towel in the crack and see if it gets wet (or worse). Jun 30, 2018 at 18:31

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