I'm looking to bury my sump pump discharge pipe from my house to the storm drain at the back of my yard, a distance of about 40 feet. I live in the Midwest, and there's already a decent slope from my house to the drain. I'll be using 4-inch PVC schedule 40 pipe throughout, with a good slope for drainage. I'm also planning to install a freeze guard where the pipe discharges. My main questions are: How deep should I bury the pipe? Is it necessary to go below the frost line given the slope? Should I add gravel at the bottom of the trench? Are there any other recommendations or materials besides PVC schedule 40 that I should consider?
5 Answers
I ran my sump pump discharge with 2-inch PVC to the basement ceiling before angling it down through the wall. That connects to 4-inch PVC for rainwater from a portion of my roof, and I've never had drainage issues even with a shallow burying. Just make sure it's sloping down correctly to avoid backflow problems!
I suggest digging at least 18 inches to allow for proper grass growth on top. If your slope is uneven, you might want to dig a bit deeper. Adding some gravel at the bottom helps with leveling. For my project, I did a mix of black single-wall drainage pipe and perforated pipe since my path wasn't completely straight. It worked out well; still, your PVC plan sounds solid if you're going straight to the drain.
Aim for at least 2 feet deep for the top of the pipe, and consider bedding it in crushed rock with some foam board on top. Anything deeper than 3 feet might be overkill, honestly. Also, while 4-inch PVC does seem a bit hefty for a sump discharge, if you’ve got a good amount of water, it should work fine!
It's not mandatory to go below the frost line as long as you have enough slope for drainage. I have a similar setup where the pipe starts off just 6 inches deep near the house but gets around 20 inches deep at the drain. It hasn't frozen during the toughest winters, even during those polar vortex occasions.
If you can, rent a trencher! I've done it by hand and with a trencher, and the latter makes the work a lot quicker and cleaner. Cutting the sod to put it back doesn't always turn out as you expect, so the trencher is a game-changer.