My house is connected to public sewer. There's a ~100ft setback between the house and the road, and in that area, there are two pipes I think are associated with the sewer. One is a white pipe coming out of the ground near the road that is well sealed, and the other is an open pipe that seems like it's meant to be allow airflow but keep rain out.

Here's that white pipe near the road: White pipe near road

Here's the other pipe, same diameter, with its lid on and off: Sewer vent in yard with lid off

Sewer vent in yard with lid on

The issue, as shown in the last two images, is that the cap for the pipe near the house is not attached at all. The diameter of the cap is about the same as the diameter of the green fitting in the black pipe, so the cap's screws have no way to get into or under the green fitting. Also, the green fitting is snugly in the black pipe but it can easily be lifted up and out of the black pipe by hand. I'm unsure if that fitting is meant to be 'locked on' to the black pipe. We've had some very windy days and surprisingly, this went undisturbed and unnoticed.

How is this meant to be setup? What part do I need to swap out to remedy this? It seems like I just need a bigger cap so it can go over the green fitting and 'lock on' to it using the green screws. I'm assuming a 'snug' fit of the green fitting into the black pipe is sufficient.

Edit in Feb 6: I confirmed this is a sewer pipe - it goes fairly deep and I see water flow through it when the shower is on. I also saw we have a sewer vent up at the roof, so this is not the only vent and might just be for access.

  • Does seem like an air vent cap, so either it needs to be bigger or the base becomes smaller. If a vent, then it should fit over the bottom and vent down the sides. Those steps inside should fit the outside of the bottom piece. Might not even need the green piece if the top fits onto the pipe.
    – crip659
    Jan 30, 2023 at 0:05
  • I suspect that its missing a bit that may have snapped into the central hole with cap around it. This would have allowed air to pass freely. Jan 30, 2023 at 2:04
  • I think that's a cleanout, not a vent.
    – Huesmann
    Jan 30, 2023 at 12:13
  • Seems unusual to have a vent down at ground-level. I'd expect both of those pipes to be closed off so as to not have sewer gasses escaping and stinking up your yard.
    – brhans
    Jan 30, 2023 at 15:12
  • There's no smell we've ever noticed. If it is a cleanout, how is it meant to be capped? For what it's worth, I don't think there is a sewer vent stack going through the roof, just a shower vent. Also this pipe is not in an area that's likely to see a lot of traffic - it's on the downhill side of a large front yard.
    – cr0
    Jan 30, 2023 at 17:45

2 Answers 2


Is it possible that you have a dry well? And that's an overflow?

The green fitting in the lawn looks like part of an overflow emitter - https://www.ndspro.com/products/drainage/pop-up-emitters.html

And the spherical cap looks like a mushroom vent cap. https://www.oatey.com/products/oatey-mushroom-vent-cap--1469620693

So I'd guess the center of the overflow got lost and someone dropped the vent cap on the hole to stop dirt/leaves washing down it.

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    – Community Bot
    Jan 31, 2023 at 13:37
  • Oh that's very possible and makes sense of this weird setup. There's a number of pipes for stormwater that go underground and we don't know where they come out of. Oddly enough, none are near this part of the lawn, so I'm not sure where the dry well would be. I'll try some tips I've read hear like playing a speaker at the opening and seeing where I can follow the sound to.
    – cr0
    Jan 31, 2023 at 13:48

The first one is a sewer cleanout. It's the last access point after your home plumbing but before the sewer drop dumps into the street line. The cap is so a plumber can access it with a snake or camera.

The second one looks to be an emitter connected to a stormwater drainage system. Generally your gutter downspouts are piped directly into PVC pipe and carried away from the foundation where the water can be discharged safely over the lawn. There is supposed to be another green plastic part on there that has broken off. The emitter caps are easy to find at hardware stores and usually just push into the pipe stub.

  • I confirmed that the pipe in between the house and the road, which had that emitter-looking cap on it, is access to the sewer pipe. So it seems we have two sewer cleanouts; one by the road, one in the yard + vent pipe coming out the roof.
    – cr0
    Feb 6, 2023 at 17:10
  • Probably someone broke the pipe with the emitter cap and just put on something they had or looked like it would fit. You should put a proper clean out cap on it. Then protect it somehow. And protect the other one, too. In my neighborhood, many of the clean outs are below ground level and in irrigation control boxes or similar.
    – longneck
    Feb 6, 2023 at 19:36

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