There's a plastic pipe with a vent cover in my back yard that runs to a green cap in the middle of the yard. What is this for? I don't have a septic tank.

pipe with vent cover

pipe cap

Update: this picture shows the entire length of the pipe that I'm aware of. The green cap from my second picture wasn't visible from this angle so I marked it with the piece of cardboard.

entire length

Update 2:

Based on everybody's comments, I felt comfortable digging it up. Here's the entire thing:

removed pipe

close up of pipe showing holes

Thanks for all the help everyone! Your comments/answers let me dig up this unused nuisance I've had to mow and trim around for far too long.

  • 1
    So, the line of the pipe from that vent goes through the cap, and presumably they're connected? Jul 3, 2016 at 19:45
  • 1
    Looks like dandelions grow well there!
    – Michael Karas
    Jul 3, 2016 at 19:54
  • Yes, the vent pipe definitely heads toward this (most of it's actually become exposed for some reason). I can't tell if the pipe goes anywhere else beyond this cap.
    – Dennis
    Jul 3, 2016 at 21:03
  • 1
    @Criggie, the ground level is definitely lower at the cap than the vent. I live in Colorado. Running water through it does eventually make the cap pop up and let the water out.
    – Dennis
    Jul 4, 2016 at 15:44
  • 1
    Since you've dug it up you may want to hang onto it for a season or two - you may find a small lake develops in the shallow around the vent-end come springtime after the winter melt. If not, then it wasn't doing anything for you at all. If so, probably better just to get some backfill delivered and grade the lot properly.
    – J...
    Jul 5, 2016 at 0:27

4 Answers 4


Looks like a rain gutter or sump pump outlet. Place a noisy device directed into it and walk around and listen.

You could probably bury the white pipe and just leave the grille exposed, flush with the lawn.

  • 2
    Good call on the noise- I placed a small speaker in the vent and walked around- the only spot I can hear it is the green cap. If I'm not having any issues with drainage in the yard, is there any harm in removing entire assembly?
    – Dennis
    Jul 3, 2016 at 21:19
  • 2
    @Dennis How long have you lived at this house? Have you been through a wet year yet? Odds are good this was installed for a reason that may or may not still be valid.
    – Myles
    Jul 4, 2016 at 16:12
  • @Myles I've been here 3 years, and have definitely been through some solid rains. That spot in the yard isn't that different from other spots, so I'm hoping it was intended for a gutter drain that's no longer there.
    – Dennis
    Jul 4, 2016 at 16:21

This could be part of a larger yard drainage system. It could let water from the screened end of the pipe drain out into some buried drain field. It could also drain onto a deep buried french drain construction consisting of a sizeable hole that was filled with crushed rock or similar.

The fact that the part of the pipe that has the screen is working its way out of the ground seems to imply that there is stress on the pipe from the end that is still buried. This could be due to settling at the buried end or the pipe was originally installed and buried by forcing it into the trench and then not covering it with enough soil. I bring this up because there is evidence that the filter screen end was buried at one time:

enter image description here

  • 2
    Good point- a lot more of the pipe is exposed now than there used to be.
    – Dennis
    Jul 3, 2016 at 22:26
  • 2
    Yeah, the opposite end seems to be one of these NDS pop-up water emitters for their drainage installations
    – Tim Stone
    Jul 4, 2016 at 13:38

It's an NDS Pro pop-up drainage emitter


I took the approach of noticing the acronym on the cap, figuring out what company it was and seeing which of their products match.


This is most likely connected to your house roof down pipe. Should be able to find out if your roof down pipes are not connected to drainage they likely go down the side of your house and enter the ground; probably a small water trap made from cement at the side of your house. The water trap will have a drainage pipe similar to phot you have shown running through your yard. Sometimes the pipes runs from your house directly to the street gutter or when this is too far or not feasible it runs the water into your yard and disperses it.

I am suprised you have not tracked the pipe back to your house??

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