DIY Air-tight Sump Hole Cover (Revisited)

Since I deleted the original site after my self-hosted website was hacked, I’ve had good intentions to resurrect some of the most popular posts that were lost. Yesterday, I received an email out of the blue from Lucie, who stumbled upon a breadcrumb of one of those posts, a reference to my “Do-it-yourself Sump Hole Cover.” So, Lucie, I’m actually achieving this because of you. Thanks!

There were actually two posts about the sump hole cover. In the first, I explained the background and steps that I followed to create the cover. In the second, I made modifications after the cover had been in use for a couple years. I’ve made some editorial revisions because, well, I write (or at least, in my imagination, I write) and that’s what writers do.

Finally, a special thanks goes to, where my original text remains preserved. This was much easier because of you!

DIY Air-tight Sump Hole Cover (originally published May 8, 2011)


The sump hole is original to the house which was constructed in 1958. The drainage tiles originally diverted downspout run-off into the sump hole, where it was pumped out. When we moved into the house, a 1/3 horsepower pedestal style pump failed twice, once during a power outage, and once when the float bent and caught, keeping the unit from kicking on. After dealing with inches of water in the basement a second time, I purchased a Basement Watchdog unit from Lowe’s. I discovered, when I installed the new unit, that the old sump pump had kept the water level high enough that the tiles were filled with water.  This meant that the tiles were always full of water: hundreds of gallons of water was always hanging out, and the difference between a flooded basement and an unflooded basement was only a few gallons. The new pump kept the water down to just inches. from the bottom of the hole. So this was the first advantage to the new pump.

Sump hole without cover

Now the downside, literally. With the water level so low, air was flowing through the tiles from outside the house (remember, the downspouts used to run into the tiles; although they don’t any more, they are only covered with grates to keep things, but not air, out). Over the last couple years after heavy rains the basement begins to smell. You can tell me: have your septic inspected; something is leaking. And you would be right. But here’s the problem: the town is installing a sewer system and every septic tank must be destroyed before the end of the summer. It would be a waste of money to dig up and fix a septic tank whose time has come. After reviewing a number of sites that discuss the advantages of their air-tight sump hole covers, I decided to make my own.

I chose to make a drain with a trap to allow the water to go down while preventing the air from coming up. Some covers I looked at on the internet used a ball and funnel type design, where water would lift the ball  as it drained, then the ball would create the seal. That seemed ingenious, except for one thing: all plumbing in houses uses traps to stop odors, so why not use the same concept here?

Here are some additional advantages to an air-tight sump hole cover: It’s supposed to stop Radon infiltration, it keeps moisture contained within the sump hole instead of spread throughout the basement, and it keeps the air that was blasting through the tiles from the outside from penetrating into the house.

Material List

  • 10 foot long 1″ x 4″ PVC trim board (cost around $17)
  • 1 PVC Trap (1 ½”)
  • 1 PVC Reducer (from 3″ to 1 ½”)
  • PVC Glue
  • Silicon Caulk
  • Assorted scrap 1 ½” PVC

Total Project Cost: Less than $50


First, let’s take a look at the original cover. It was constructed from assorted pieces of 2x treated lumber. It was not sealed and was constantly wet since water drained onto it. BUT, it kept my children from falling into it.

Original sump cover made from treated wood
  • I decided that like the original wood cover, the PVC cover should run from the north to the south (left to right in the picture). Any cut-outs needed to be set into a side of the trim board rather than cutting the board in two. Using the existing cover as a template I cut the PVC trim board to width and used a jigsaw to make rough openings for the sump pump.
  • I traced the PVC reducer and used a jigsaw to cut an opening for it. I actually meant to have it on the other side, but due to a mix-up in what is up and what is down, cut it on the opposite side I meant. Since the location of the drain was nothing more than a preference, I didn’t worry about it. If I had cut the hole for the sump pump itself, however, that would have been another story…
  • I edge-glued the trim boards and put the trap together with glue. I glued two pieces with the idea that I would seal the remaining edges with caulk so I could remove it as needed.
Underside of sump cover, including PVD drain with trap
  • I used caulk to line the perimeter of the sump hole as well as the edges where the two pieces would meet, then set both pieces in the sump hole.
  • I ran another bead of caulk around the perimeter, smoothing the edges to seal.
  • I cut additional pieces to stair-step and glue to form tight fit around the PVC from the sump pump.
  • I caulked the remaining gaps.
  • I then bought assorted PVC to re-route any drains (in this case, the furnace and the reverse-osmosis units) to run directly into the drain. The remaining PVC line that doesn’t make it to the drain in the photos is from the softener, which isn’t running at the moment. When I have it running it will also extend to the drain.
Finished sump cover
Finished sump cover detail

Final Thoughts

Since the cover was installed there has been no smell in the basement. The cover may also help the humidity, and if so, that will mean running the dehumidifier less, which will be a cost savings also.

Disclaimer: This page is not intended to replace the advice of a professional. It simply relates what I did. And what I did may be wrong. That’s one of the ways I learn, by trying things and discovering that I did something wrong. I’m a lot smarter now than I was five years ago, and I hope I’ll be even smarter five years from now.

DIY Sump Hole Cover Redux (Originally published on July 22, 2015)

Previously I explained how to build your own do-it-yourself air-tight sump hole cover using PVC, glue, and caulk. Since then, my sump cover met its match when it tried to swallow a ping-pong ball. The more I tried to remove the ping-pong ball from the inside of the 1 1/2″ PVC trap, the more the trap became blocked; the end result was I had to remove the entire sump hole cover to get the ping-pong ball out of the drain. This proved particularly troublesome since there was no convenient way to pull the cover off. In the end I was forced to drill a hole in the cover and use an L-shaped piece of metal inserted into the hole to give me pulling power to remove the cover; otherwise I couldn’t find any way to get the cover off.

Before re-attaching the cover I decided to make some minor improvements that were not incorporated in the initial design. Obviously the first modification needed to be a handle so the cover can be removed when necessary.

Three additional ping-pong balls had found their way into the sump hole while the cover was off (plus two Nerf balls). The drain needed some kind of cover or screen to prevent anything from blocking it.

One thing that had always bugged me about the original cover was that I could not see anything going on inside. How much water was sitting in the hole? It was always a mystery, and the only way to know what was going on in the covered hole was to listen to the water trickling in or the pumps running. A window to see into the sump hole would be an ideal addition to the design.

First Modification: Handle

I attached a handle to part of the cover. Rather than use the screws that came with the handle, I bolted it all the way through the cover. I caulked the bottom and top before tightening the screws and bolts.

Attach handle using bolts.

 Second Modification: Drain Cover

This choice was really a matter of convenience. I needed something to fill the drain, but I didn’t want a screen that could get blocked with lint or dust or dirt. I tried looking around the house for a ball, something larger than a ping-pong ball that would float and create a barrier to keep out ping-pong balls or other smaller objects, but nothing that I came across worked. As I was standing at my workbench, I noticed an empty seltzer bottle in the garbage can. I thought, why not? And I cut the bottom from it.

Remove bottom from plastic bottle.

Next, I used tin snips to cut triangles between the ridges of the base:

Use scissors or snips or a razor blade to remove triangles from the base of the bottle.

Finally, I set the bottle cut-side down in the drain. It fits; water will flow down over it and through the cut triangles without any risk of ping-pong balls getting in.

Set plastic bottle base cut-side down into drain.

Is it elegant? No. Is it going to win design awards? Does it look like HAL2000? Not really. But does it work? Yes.

Third Modification: Window

Inserting the window from the beginning would have been preferable to adding it after the pieces had all been glued in place. Ideally I would have cut the opening for the window, then routed a lip to recess the plastic. This was after-the-fact, however, so ideal wasn’t going to happen. I was going to have to resort to a plain, old jigsaw hole.

For the window I found a $4 piece of Lexan plastic at Menards.

Lexan plastic for sump window

I used a square to scribe a rectangle on the plastic:

Mark the rectangle to be removed.

Then I used a drill to give my jigsaw a place to start and cut out the rectangle:

Drill starter hole.
Use jigsaw to cut rectangle from plastic.
Finished hole

While there may be recommended tools to cut Lexan, I simply used an X-acto knife and a straight edge. After scoring the plastic a number of times, I bent it until it snapped. This is the step that could probably result in a painful injury, so for heaven’s sake, be careful! After cutting the plastic, I found that my hole was 1/8″ too short, and it was easier to use the jigsaw to remove an additional 1/8″ than try to re-cut the plastic.

Cut plastic ready to be inserted

I spread plastic wrap on the work area. After placing the cover face down, I set the cut Lexan into the opening, then applied the silicone caulk to the perimeter. Again, I’ll mention that ideally there would be a lip around the perimeter that would hold the plastic level to the surface of the sump cover; this method only holds the plastic in place with caulk, so it cannot support weight. Hopefully you aren’t standing on your sump cover anyway.

Set plastic into opening.
Caulk perimeter and let dry.

Once the caulk dried, I put a second layer of caulk around the plastic on the other side of the cover.

Set Cover

I cleaned the area around the sump hole and ran a fan on it for a couple hours to dry it out before setting the cover in place.

Prepare sump hole for the cover by cleaning and allowing drying time.

I ran a bead of caulk around the perimeter, but with the variations in the lip from age and deterioration, some sections did not allow for a good seal.

Apply a bead of caulk to perimeter of sump hole.

Something I failed to mention previously was that I realized after I installed the cover the first time that the sump hole was not level; water that ran onto the cover didn’t run straight to the drain; instead, it pooled on one side. I used this opportunity to make sure the cover sat in such a way that the water would be directed toward the drain. Running a second bead of caulk around the perimeter and on every seam insured a snug fit and a good seal.

Finish the cover by adding caulk between the pieces, to the perimeter, and along every seam.
Detail of the drain in use: no ping-pong balls are going in here!
Finished DIY air-tight sump hole cover


If you are fortunate enough to have a prefabricated sump hole unit, there may be covers available for cheap that will save you the stress and time of building your own. Most everything I found online was for round sump holes; many did not include drains, or were not air-tight. If you have a house like mine that was built in another era (mine is from the 1950s), building your own may be the best option. I suppose it’s possible this sump cover is not 100% air-tight, but it has to be pretty darn close. Plus, this is the only cover I see that incorporates a window to see into the sump hole.

What do you think? I’d love to hear your stories or feedback. Leave me a comment below!

Compulsory Disclaimer: This post does not take the place of professional advice; it simply describes what I did. I am in no way responsible for you, your choices, your experiences, and your problems. In other words: use at your own risk!


  1. This is awesome !
    Just bought my first house and what do you know!….. there’s a rectangular hole for my sump and everywhere I look they are trying to sell me a round bucket … lol

    This is a great idea that I will be using very soon. Instead I think I will use a thick piece of plexi glass for the whole thing.

    Thanks for sharing !



    1. I’m glad you found this helpful and can adapt/improve it for your new home. Congrats on the new home and the many projects that are in your future!



  2. Hi Andrew, I’m really glad you managed to “revive” the post (I’m the Lucie you mentioned at the beginning). Now that I have those instructions in full,. I’ll be able to re-design/complete my sump pit. Thanks a million!



  3. Hi Andrew, this looks awesome I am not understanding the reasoning behind the handle. Did you do it so it will be able to remove the cover if needed? Since the sounding is covered with caulking you won’t be able to open it on the fly correct. Anyways looks amazing!



    1. Thank you, Sam.
      When I originally installed the cover, I didn’t imagine the time when I would want to remove the cover, but after a ping pong ball got lodged into the trap, it turned into a real beast trying to get the cover to lift off with the perimeter both caulked to the ledge and around the edges. I thought I’d add the handle for the next time some reason came up when I would need to remove the cover. Thankfully, I haven’t had to do so since.
      You are correct that I did not install it to be removed on the fly.



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