Crawl spaces and basements
Sump pump installation, with battery backup
A sump pump is the part that actually removes water. Drains gather it, the basin holds it and the pump pushes it outdoors. It may sit under a crawl space liner or in a basement corner. Either way the parts are the same, and so are the ways an installation falls short.
Call (205) 555-0115Drawing
What is in the pit
- Basin. A perforated or solid liner set into the ground at a low spot. Drain pipes empty into it and a lid keeps damp and debris in their place.
- Main pump and float. Runs on house current. The float rises with the water and switches the pump on.
- Check valve. A one-way valve on the pipe so water already pumped up cannot fall back into the basin.
- Discharge pipe. Carries the water through the wall and releases it away from the house.
- Backup pump. A second pump mounted higher. It starts only if the water rises past the main pump's level.
- Battery and alarm. The battery runs the backup when the power is out. The alarm tells you it has started.
Why the backup is not an extra
The storms that fill a basin are the same storms that bring down power lines. A pump with no electricity is a bucket with a lid. A battery backup covers that gap for as long as its charge lasts, and it also covers the day the main pump's float sticks or its motor fails.
Backup systems differ in how much water they can move and for how long. Ask for both figures and for the age at which the battery should be replaced. A battery of unknown age is not a backup. Write the fitting date on it.
Where the water is sent
The discharge pipe should end on your own ground, downhill from the house, far enough out that the water does not run straight back to the foundation. It should not pour across a sidewalk or onto the lot next door. A buried pipe to a pop-up outlet in the lawn keeps it tidy, and burying pipe means the 811 notice applies before the trench is dug.
Do not accept a plan that empties the pump into a floor drain or a laundry sink. Those lead to the sewer or a septic tank, which are not built to take groundwater. If someone proposes connecting to a street storm drain, that is the city's pipe, and the city's stormwater staff are the ones to ask. Their number is on the local rules page.
What fitting one involves
In a basement, a hole is cut in the slab at a low corner, the basin is set in gravel and the floor is patched around it. In a crawl space the basin is dug into the dirt before any liner is laid. A hole is drilled through the outside wall or the rim of the house for the pipe.
The pump needs its own outlet within reach of its cord. If there is none nearby, an electrician adds one, which is a separate trade and may need its own permit. An extension cord is not an answer for a pump.
A pump on its own, with no drain feeding it, only helps if water naturally collects at that one spot. More often it is one piece of a drain system, described under basement waterproofing and crawl space repair.
Ask about the pump
- What make and capacity is the main pump, and what kind of switch does it have?
- Is a backup pump with a battery in the price, or optional?
- Is there a check valve, and can it be reached for replacement?
- Where exactly will the pipe come out, and where does the water go from there?
- Is the lid sealed, and does it have an inspection port?
- Who do I call if it stops, and what does the manufacturer's warranty cover?
Keeping it working
Test it before the wet months. Lift the lid, pour in a bucket of water and watch the float rise, the pump start and the water level drop. Then unplug the main pump and repeat to see the backup do the same. Check that the outlet outside is not buried under mulch or leaves. If the pump hums and moves no water, or starts and stops every few seconds, have it looked at before the next storm, not during it.
Sump pump questions
My pump runs constantly. Is that a fault?
It can be a stuck float, a failed check valve letting the same water return, or a high water table after long rain. If it runs in dry weather, it needs attention. A leaking water pipe nearby can also feed a pit without anyone noticing.
Can I replace a pump myself?
A like-for-like swap is within reach of a handy owner. Adding a basin, a discharge route or a backup system is installation work, and it is where most mistakes are made.
Do I need one if I have never had water?
Probably not. A pump solves a water problem you have. A basin with nothing draining into it is a hole in your floor.
Is a water-powered backup an option?
Some backups run on city water pressure, not a battery. They need a reliable municipal supply and a plumber to fit them. Ask whether one suits your house.