How Do I Install a Sump Pump Discharge Line?

Connected to your sump pump, the discharge line is the pipe that carries pumped water away from your home. Discharge lines are most commonly 2”, 3” or 4” PVC pipe, and typically they are buried underground so they’re out of the way and not visible from outside the home. 

How Long Should the Discharge Line Be? 

A properly installed discharge line will deposit water as far from the home’s foundation as possible. This seems like common sense, but a lot of homeowners and contractors fail to drain the water any significant distance from the house — causing the water to pool around the foundation or flow back into the sump basin, where it has to be pumped out all over again. 

That defeats the purpose of having a sump pump system in the first place, puts unnecessary wear and tear on your pump, and risks costly pump failure and water damage to your home. 

To protect your investment, your discharge line must be both properly installed and long enough to dump the water in either a discharge field (sometimes also called a drain field) located a safe distance from the foundation, a ditch, a storm drain, or another appropriate location.

Minimum Length of Sump Pump Discharge Line 

This varies from property to property, depending on factors like the slope of the lot and the type of soil. A common recommendation is at least 10 feet, but many discharge lines run 20 feet or more. 

The discharge line should be installed so that it drains downhill, making backflow impossible. As long as your property offers a downward slope from the opening of the discharge line away from the house, even if the discharge line is relatively short, your system should work as designed.

If the landscaping around the house is flat or slopes down toward the foundation, regrading the yard might be necessary to create a good discharge field for your sump pump system.

How Do I Extend a Discharge Line?

If your yard gets flooded — or a wet, marshy, spongy, muddy patch develops — whenever the pump runs, you may need to extend your discharge line to relocate the discharge field and allow the yard to dry out.

Fixing this problem is a multi-step process: identify locations of utility cables, choose a new path for the discharge line, dig a trench along that path, lay and connect the additional lengths of pipe, then backfill the trench. This video by Get It Done Home Repair details all of these steps.

How Deep Should the Discharge Line Be Buried?

The appropriate depth for your sump pump discharge line depends on where you live — the line should be buried shallow enough to allow easy digging and future access to the pipe, but also safely below the frost line— the depth to which soil freezes in winter — in your area. This is because if water in the pipe freezes, it will block the line and potentially damage the pipe itself, and your sump pump won’t be able to remove water from your home. 

For this reason, install your sump pump discharge line 2 feet below the frost line. In most areas this means the line should be buried 2.5 to 4 feet underground, but in especially cold areas the pipes could need to be buried as deep as 8 feet.

Wikipedia’s frost line page offers good basic information about frost lines in North America. 

If deep burial isn’t an option, use the largest diameter pipe available (usually that’s 4 inches) and make sure there is sufficient slope — ¼ inch to ½ inch per foot of pipe — down and away from the foundation to ensure the water moves quickly to where it needs to go. If the pipe is large enough and the slope steep enough, gravity should move the water fast enough that it won’t freeze.

Where Should the Sump Pump Discharge Line Drain?

Your Own Property

Ideally, a sump pump discharge line feeds into a natural stream or creek bed on the property, delivering the pumped water well away from the house into a natural feature that already serves the purpose of transporting rainwater. Not every property allows for that kind of setup, of course. 

For most homeowners, the next-best option is a low-lying area of the yard, on a slope that will carry the water down and away from the house without directing it onto a neighbor’s property or a paved surface. The end of the pipe can be protected with a grate or a pop-up emitter, partially disguising it and keeping out animals and debris that could clog the discharge line. This video shows installation of a discharge line with a pop-up emitter.

These are just two options for directing water away from your house, though. There are many other legal, environmentally friendly solutions, such as rain gardens, storm drains, ditches, and dry wells.

Rain Garden

A rain garden is a small area designed to allow rainwater (or sump pump discharge) to collect and soak into the soil. This creates a small oasis in the yard that can support a lush variety of plants, which will eventually attract beneficial birds, insects, and animals.

Storm Drain

Directing the sump pump discharge line toward the street, where it can flow into the storm drain, is another good option for homeowners whose properties are situated along paved, curbed streets.

Drainage Ditch or Easement

If your neighborhood was built with a drainage ditch or drainage easement adjacent to your property, this could be another good drain field for your sump pump system — particularly if your yard isn’t graded to allow water to flow freely to the ditch or easement on its own. 

Consult your homeowner’s association and local authorities to make sure you can safely (and legally) direct your pumped water into the ditch or easement; there could be requirements around pipe placement.

Dry Well 

A dry well is a large hole filled with crushed stone and a covered, barrel-like structure designed to disperse water deep underground. At the center of the dry well is a plastic barrel with small holes in the sides and a single large hole through which the sump pump drainage line enters. When the pump removes water from the sump basin, it collects in the dry well and is then slowly released into the ground. This video by This Old House details the dry well installation process.

Where Should You NOT Discharge Your Sump Pump Drain Line?

Your Neighbor’s Property

Take care not to direct your discharge line in such a way that water flows into adjacent properties. Doing so could make you liable for any flooding damage caused by discharge from your sump pump.

Sanitary Sewer

This might seem like an obvious location for your sump pump discharge line to drain, but hooking your sump pump discharge line into the local sanitary sewer system is actually illegal in most places. The reason? Sanitary sewer systems simply aren’t designed to handle the volume of water collected by sump pump systems in addition to sinks, showers, toilets, washing machines, and everything else connected to them. If everyone were to hook up their discharge lines to the local sanitary sewer system, the city’s water treatment facilities would get overwhelmed with every significant rainstorm. 

If that’s not enough reason not to illegally connect your sump pump system to your city’s sanitary sewer, consider this: Under enormous pressure from heavy rains and flooding, sewer systems are known to back up. If your sump pump system were connected to the city’s sewer pipes, you could find yourself with a basement (or house) flooded with raw sewage.

Your Septic System Leach Field

If your house is on a septic tank, avoid routing your sump pump discharge into your septic field, where the additional water from heavy rains or flooding could cause problems with that system.

Paved Surfaces

Water flows quickly — and often destructively — across paved surfaces, where it’s free to accelerate or pool, depending on the surface. It can cause erosion where it meets natural landscape, or it can pool and create hazards for car or foot traffic. For these reasons, avoid directing your discharge line in a way that sends water across a sidewalk, street, or driveway. There is always a better option.