How to Install a Sump Pump

Sump pump plumbing comes down to four things done right: a level pit, a 1-1/2 inch discharge line, a check valve set just above the pump, and a legal discharge point well away from the foundation. Learning how to install a sump pump takes a few hours, basic PVC tools, and a GFCI outlet. Here is the full sequence, with the specs that matter.

Sump pump parts and specs at a glance

Before you cut any pipe, stage every part. A standard residential setup uses a 1/3 to 1/2 HP pump, a 1-1/2 inch PVC discharge line, a check valve, and a 3/16 inch weep hole. The table below maps each component to its spec and why it matters, so nothing gets skipped when you install a sump pump.

One code point drives the whole discharge plan: in most US areas you cannot route sump water into the sanitary sewer, and you should never send it to a septic system. Storm water overwhelms treatment and drainfields. Where the water can legally go (yard, storm drain, or a dedicated line) varies by state and local code, so confirm whether your job needs a permit and call your building department before you glue anything.

Submersible or pedestal: which pump fits your pit?

Pick the pump before you size the pit. Submersible pumps sit in the basin underwater and run quiet, which suits most finished basements and higher water tables. Pedestal pumps keep the motor on a shaft above the pit, cost less, and squeeze into narrow basins, but they are louder. The comparison below shows the trade-offs.

How deep and wide should the sump pit be?

Size the pit for the float, not just the pump. Aim for about 18 inches in diameter and 22 to 24 inches deep from the finished floor, which gives the float enough vertical travel to cycle cleanly. Put 6 to 8 inches of gravel under the liner for drainage, but seat the pump on a paver or brick so the impeller never sits in silt.

How to install a sump pump step by step

Work the job in order, dry-fitting the discharge before you cement it. The steps below assume a new pit; for a swap, jump to the replacement section. Keep the pump on a solid base, keep the float clear, and test with real water before you call it done.

1. Cut power at the breaker and confirm the circuit is dead. Choose a low corner near a GFCI outlet where water collects.
2. Mark the basin outline, break the slab, and dig the pit 22 to 24 inches deep and a few inches wider than the liner.
3. Add 6 to 8 inches of gravel, wrap the liner in landscape fabric, set it level, and backfill the gap with gravel or concrete.
4. Set the pump on a paver or brick in the pit so it sits flat. Confirm the float switch swings freely and clears the walls.
5. Thread the discharge adapter onto the pump outlet and dry-fit the 1-1/2 inch Schedule 40 PVC riser.
6. Install the check valve 8 to 12 inches above the pump with its arrow pointing up, then clamp or cement the unions.
7. Drill a 3/16 inch weep hole at a downward angle in the riser below the check valve to prevent air-lock.
8. Run the discharge through the rim joist or wall, pitch it downhill, and terminate it 10+ feet from the foundation.
9. Seal the wall penetration, secure the cord with ties (never an extension cord), and plug into the GFCI outlet.
10. Pour water into the pit until the float trips. Confirm the pump starts, empties the pit, shuts off, and the check valve holds.

Where does the discharge line go, and where it cannot?

The discharge has to move water away for good, not in a loop. Pitch the line downhill and end it at least 10 feet from the foundation, farther on flat lots, so water does not seep back to the pit. In many areas you can send it to the yard or a storm system, but rules on distance, property lines, and storm-drain tie-ins vary by local code.

What is nearly universal: sump water may not go into the sanitary sewer, and it should never feed a septic system. This is a groundwater pump, not a waste pump. If you are moving sewage from below the sewer line instead, that is a sewage ejector pump, a different job entirely, and common when adding a below-grade basement bathroom.

Where do the check valve and weep hole go?

These two parts protect the motor, so placement is not optional. Set the check valve on the vertical riser 8 to 12 inches above the pump outlet, below the first bend, with the flow arrow pointing up. Drill the 3/16 inch weep hole between the pump and the check valve, angled down, so trapped air can bleed off.

Skip the check valve and the column of water in the pipe drains straight back after each cycle, refilling the pit and re-triggering the float. That short-cycling wears the motor out early. Skip the weep hole and the pump can air-lock, spinning without moving water. Both parts cost a few dollars and add years of service.

Do you need a battery backup?

If a wet basement would cost you, yes. Storms cause the flooding and the power loss at the same time, and a primary pump on a dead circuit does nothing. A backup system adds a second pump on a deep-cycle battery that takes over automatically. Add a high-water alarm so you hear a problem before the water shows up.

Replacing an existing sump pump

Swapping a worn pump into a good pit is faster than a new install, often under two hours. Match the new pump to the old discharge height so you reuse the existing pipe. Inspect the check valve while you are in there and replace it if it is stiff or leaking. Follow the short sequence below.

1. Shut off the breaker and confirm the pump is dead with a voltage tester before touching anything.
2. Disconnect the discharge at the union or above the check valve, then unplug and lift the old pump out.
3. Scoop sludge and debris from the bottom of the pit so the new impeller stays clear.
4. Set the new pump on the base, level it, and reconnect the discharge, replacing the check valve if worn.
5. Restore power and test with a bucket of water until the pump cycles on and off cleanly.

When should you call a plumber?

DIY covers most pump swaps and many first installs. Call a pro when the slab must be cut for a new pit, the discharge needs rerouting or burying, you want a backup system wired in, or your area requires a licensed installer. For budgeting either route, see what a sump pump costs before you decide.

Frequently asked questions

Do you need a plumber to install a sump pump?

Not always. Swapping a pump into an existing pit with a working discharge line is a common DIY job that runs a few hours. Hire a plumber if the discharge needs rerouting, the slab must be cut for a new pit, you want a battery backup with automatic switchover, or local code requires a licensed installer and permit.

How deep and wide should a sump pit be?

A standard residential pit is about 18 inches in diameter and 22 to 24 inches deep, measured from the finished floor. That depth gives the float enough travel to cycle without short-cycling the motor. Set 6 to 8 inches of gravel under the liner for drainage, but the pump itself must rest on a solid, level base.

Can a sump pump drain into the sewer?

In most US areas, no. Local code usually bans routing sump (groundwater) discharge into the sanitary sewer because storm water overwhelms treatment capacity, and it can flood a septic system. Discharge typically goes to the yard or a storm system where allowed. Rules vary by state and city, so confirm with your local building department before you plumb it.

Where should the check valve go on a sump pump?

Install the check valve on the vertical discharge pipe, roughly 8 to 12 inches above the pump outlet and below the first bend. The arrow on the body must point up, in the direction of flow. This spot stops pumped water from draining back into the pit and leaves room to drill the weep hole beneath it.

What size is a sump pump discharge pipe?

Most residential pumps use a 1-1/2 inch discharge line in Schedule 40 PVC, matched to the pump outlet. Some larger 1/2 HP or higher pumps step up to 2 inch. Never reduce below the pump outlet size: a narrower pipe chokes flow, makes the motor work harder, and shortens its life.

Submersible or pedestal, which sump pump should I install?

Submersible pumps sit in the pit underwater, run quieter, and handle higher inflow, which suits most finished basements. Pedestal pumps keep the motor on a shaft above the pit, cost less, and fit narrow pits, but they are louder. For heavy water tables or a living space below grade, a submersible is the usual pick.

Do I need a permit to install a sump pump?

It depends on your area. Simply replacing a pump in place often needs no permit. New pits, new discharge lines, or any electrical work more often trigger a permit and inspection, especially where the discharge ties into a storm system. Check with your local building department first, since requirements and fees vary by state and city.

Last reviewed: September 2026.