Just had my sewer line redone in my basement and when they poured in the concrete it created a trapezoidal shape and the dimensions are not standard. This is similar to covering a sump pit in the basement, but in my case, it's the cover over the house traps on 2 sewer lines and covers an area bout the size of a bath towel. 36" long and 18" wide on the narrow end, 24" wide on the wider end.

enter image description here

What's the best material to make a lid/cover from. Should I just cut plywood and call it a day, or is there an easy inexpensive plastic or metal that I can get custom cut to size? Maybe a large plastic lid or something I can shave down or just lay on top and anchor in some way? I don't have a lot of tools so something that can either be ordered cut to size or modified with simple at-home tools would be great.

I'm thinking I can either cut the wood to size, or get a larger metal sheet that I just lay over the entire shape and not have it be something that's custom fit. Does it need to be flush to the ground for some code issue that I don't know about?

  • 3
    I'm not clear what you are attempting to cover. A "sewer line" should be a pipe that is fully enclosed. It should have a cleanout but that should have its own cover. Perhaps a photo or two of what you have here would be helpful.
    – jwh20
    Commented Oct 7, 2021 at 12:44
  • "Flush to the ground" - not sure about code but the lawnmower may find it if it is not flush...
    – Solar Mike
    Commented Oct 7, 2021 at 13:39
  • I added pictures of other examples (that are not mine), it's in the basement and it's irregularly sized and a bit bigger in area than the nice ones in the photos. Commented Oct 7, 2021 at 16:23
  • What goal are you trying to achieve by covering this? Should people be able to walk on it, put things on it, or is it just for aesthetics? That would in part dictate the material. Commented Oct 7, 2021 at 16:31
  • 1
    It should be strong enough to stand on, whether or not you care about that. Depending on size and material it might need additional support or structure underneath. Does it have to be flush? Depends on the location. Don't create a trip hazard. Photos of your actual situation would help.
    – jay613
    Commented Oct 7, 2021 at 16:49

2 Answers 2


New answer, based on your new picture.

Cut a sheet of 3/4 inch plywood to fit the opening. Enforce it underneath with wood or with L shaped bars normally used for shelving. Connect wooden legs that will fit in the four corners of this pit so they rest on the bottom. So you have something constructed like a simple table, but not rectangular, fitting flush inside the opening and sitting on the bottom in the corners.

The enforcement may not be necessary. The legs can be attached to the cover so they come out with it, or they can be attached to the pit walls so they just support the cover.

Another option if the plumbers are still there and they have the ability to grind and set concrete is to ask them to create a groove around the top that is rectangular overall, at least 2 inches bigger than the hole all around, and 3/4 inch deep so you can just drop a rectangular piece of 3/4 inch plywood in it.

What I mean is this: They dig a groove 3/4 inch deep all around the pit up to the red line. Where the line is CLOSEST to the pit, it should have some minimum overhang like about 2 inches. Then you just drop a piece of 3/4 inch plywood on it, with a 1/2 inch hole cut out as shown for pulling it out. The environment is probably damp so you can paint the board with a suitable protective paint in the color of the basement floor.

enter image description here

  • so the concrete guy said that he'll come back and cut out a groove for me when I get a lid - and that he'll make the groove rectangular so that I wouldn't have to deal with the weird shape - which I kind of can picture if he just shaves down 6" of top surface from the narrower end. Commented Oct 8, 2021 at 20:01
  • That's great. Not sure what you mean about six inches. I've added a picture of what I mean to my answer.
    – jay613
    Commented Oct 8, 2021 at 20:20

EDIT: Leaving this answer here for posterity but now that you have updated the photo in the question to show your own actual situation, I see the pit has already been formed in concrete so you cannot use a valve box.

An easy way to do this is with valve boxes. They come with flush-fit lids that are strong enough to stand on. They are CHEAP. If you have a large or odd-shaped area you can use multiple valve boxes next to each other. You can safely cut out chunks from the sides to provide a single large internal space as long as you leave enough structure to support the lids. You can get different color lids (black, grey, brown) too.

It's important to note that in your photos, and presumably in your actual situation, the traps and pipes are all fully sealed. This is not a sewage pit. It is just an access cover to equipment that is located below floor level. So it does not require a sealed cover.

Valve box

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