Sump Pumps and Sewage Ejectors for Trades in the Basement
Why this matters
Every basement trade eventually needs a receptacle, and the one beside the pit in the corner looks free. It is the pump's. Unplug it in a rainstorm and the basin can overflow onto the floor you came to install in less time than it takes to cut a few boards. Open the wrong lid to "see what's in there" and you are breathing sewer gas. This card shows how to tell a sump pump from a sewage ejector, why neither gets unplugged, why a sealed lid stays sealed, and what a running or alarming pump is telling you.
For what each basin is designed to handle and why they are built differently, see related: What a Sump Basin and a Sewage Ejector Basin Each Have to Handle.
First, if there is water on the floor
A basin that has overflowed puts water on the floor around cords, receptacles and the pump itself. Do not step into standing water that reaches a cord, a receptacle, an extension cord or any equipment that could be energized. Stay out of it, keep others out, and tell the homeowner; if the water is up to receptacles or the panel, the call is an electrician or the electric utility to de-energize before anyone wades in. If the water came from a sewage ejector, it is sewage: no bare skin contact, and nobody cleans it up without gloves, boots and a plan for disinfection.
Telling them apart
| What you see | Sump basin | Sewage ejector basin |
|---|---|---|
| What flows in | Groundwater from drain tile around the foundation | Waste from basement fixtures below the sewer line |
| Lid | Often loose, clear or perforated; sometimes sealed | Sealed, gasketed, usually bolted down |
| Pipes through the lid | One discharge pipe | A discharge pipe and a vent pipe, often both 2 in or larger |
| Where the discharge goes | Outside, to the yard or a storm connection | Into the house's building drain or sewer |
| What is nearby | A dry basement corner | A basement bathroom, laundry or bar sink |
| Smell | Earthy or none | Sewage, if the seal leaks |
One trap: a sealed sump. A sump lid sealed down with a pipe rising from it to a small fan, often with a little U-shaped liquid gauge on the pipe, is probably part of a radon mitigation system using the sump as its suction point. It is sealed for a different reason, and it stays sealed for that reason too.
A third pump people miss: the laundry tray pump. A small box or basin under a laundry sink, with its own little pump, lifts the washer's and the sink's water up to a drain overhead. It is sized for gray water only, and it gets the same treatment as the other two: its plug stays in, because the next time the washer drains, that water has nowhere to go but the floor. A condensate pump beside a furnace or air handler is the same idea at a smaller scale, and it belongs to the HVAC trade.
Both have floats. A float is the switch that turns the pump on as water rises and off as it falls. Many pumps use a piggyback plug: the float switch plugs into the wall, and the pump's own cord plugs into the back of the float's plug. Some basins also have a separate high-water alarm on a cord or a small box on the wall.
Why you never unplug either
The pump is only as good as its power. A sump pump with no power does nothing as groundwater keeps arriving. An ejector with no power lets waste rise in the basin every time someone upstairs uses a basement fixture, or a laundry machine drains into it.
Unplugging the piggyback breaks the float too. Pull the plug out of the wall and both the float and the pump are off. Pull the pump's cord out of the back and plug your saw in there, and the float now runs your saw.
The circuit is often a GFCI. NEC 210.8, as adopted, has extended GFCI protection to basement receptacles over recent editions, so the pump may sit behind a GFCI receptacle or breaker. Your tool tripping that GFCI turns the pump off as surely as pulling the plug, and nothing tells you. If you trip one, unplug your tool and reset it right away; if it will not hold or trips again, tell the homeowner, who calls an electrician.
A battery backup pump is not a spare. A second pump with a battery and a charger may sit in the same basin. It is there for a power outage, and it runs for a limited time on its battery. Unplugging the main pump hands the job to a backup meant for emergencies, and unplugging its charger lets the battery run down.
Why the sealed lid stays sealed
An ejector basin holds raw sewage and the gases it gives off, including hydrogen sulfide, which deadens your sense of smell at harmful concentrations, and methane. The lid's gasket and the vent pipe keep those gases out of the basement and send them up through the roof. Unbolt the lid and you release them into a room with no ventilation, expose yourself to sewage by every route at once (splash, contact, hands to mouth), and probably break a seal the owning trade then has to remake. If you smell sewage near an ejector, the seal or the vent has a problem: open a door or window if one is handy, leave the area, and tell the homeowner to call a plumber.
The same goes for a sealed radon sump: lifting the lid defeats the system and lets soil gas into the basement.
What running and alarming mean
A sump pump that runs often during and after rain is usually doing its job. One that runs every few minutes in dry weather may have a failed check valve (water in the discharge pipe falls back into the basin after each cycle and gets pumped again), a stuck float, or an unusually high water table. One that hums without pumping, or never stops, may be jammed or failing. All of those are the homeowner's call to a plumber or waterproofing contractor; you do not adjust floats or tap on pumps.
A sump high-water alarm means water is above where the pump should have handled it. Tell the homeowner at once.
An ejector alarm means waste is backing up in the basin. Stop using the basement fixtures that drain into it (toilet, shower, sink, and the washer if it empties there), tell the homeowner, and they call a plumber. Do not open the lid to look.
Worked example: the extractor that needed a receptacle
A flooring installer is putting a click-lock floating floor in a finished basement on a rainy day. The dust extractor for the saw needs a receptacle. The closest one is a duplex beside the sump basin in the corner of the utility area. The top outlet carries a piggyback plug; the bottom carries a battery backup charger.
What the pump is doing. The installer watches for a few minutes. The pump kicks on, runs, and shuts off; the water then rises again from the off level to the on level in about 3 minutes, over and over. The lid is clear plastic, so he can see the water line. The basin is 18 in across and 24 in deep. With a tape held to the clear lid, the pump shuts off with water 8 in up from the bottom and turns on at 13 in, a 5 in rise.
How much water that is. The basin's floor area is pi x 9 in x 9 in, about 254 square inches. A 5 in rise is 254 x 5 = 1,270 cubic inches, and at 231 cubic inches per gallon that is about 5.5 gallons. Filling that in 3 minutes is about 5.5 / 3 = 1.8 gallons per minute coming in from the drain tile.
How long until it overflows unplugged. From the off level at 8 in to the rim at 24 in is 16 in. That is 254 x 16 = 4,064 cubic inches, about 17.6 gallons. At 1.8 gallons per minute it reaches the rim in about 17.6 / 1.8, so roughly 10 minutes. Checked the other way: a 5 in rise takes 3 minutes, so 16 in takes about 16 / 5 x 3 = 9.6 minutes. Under ten minutes, which is less time than the installer would spend on a few cuts before remembering to plug the pump back in.
The decision. Neither outlet on that duplex gets touched. The installer asks the homeowner for another circuit, uses a receptacle in the laundry on a different breaker, and runs a heavy cord. He keeps the cord's connection off the floor and away from the basin.
What changes the answer.
- Dry weather. Say the water rose off to on in 40 minutes instead of 3. Inflow is 5.5 / 40, about 0.14 gallons per minute, and the 17.6 gallons to the rim take about 128 minutes. More time, but the pump still does not come unplugged: nobody knows when the next rain starts, and two hours passes quickly on a floor job.
- The same duplex next to an ejector instead. Inflow is not weather; it is whenever someone uses a basement fixture. The installer is not using them, but a washer upstairs on a timer may drain into it. Same answer, and the overflow is sewage rather than groundwater.
- The only receptacle on the floor is the pump's. Then the installer brings his own power from upstairs or a generator outside, not the pump's receptacle. It is not a judgment call.
The failure mode. Not the pump failing on its own. It is the plug pulled for "one cut", the phone call that comes in, and 10 minutes later a basin spilling across a new floor, with the installer's cords in the water.
Before you leave the basement
- Both pumps' plugs where you found them, and the GFCI not tripped (look at its indicator if it has one).
- Nothing set on either lid, and nothing blocking access to the basin.
- No new flooring, trim or underlayment sealing over a basin lid or covering the access to it. A basin covered by a finished floor is a basin nobody can service.
- Anything odd (constant running, an alarm, a smell) told to the homeowner and written on your ticket. See related: How to Hand Off a Problem You Found in Another Trade's System.
References
- NFPA 70, National Electrical Code, 210.8 (GFCI protection), in the edition your jurisdiction has adopted
- The pump's and alarm's manufacturer documentation
- See related: What a Sump Basin and a Sewage Ejector Basin Each Have to Handle
- See related: Drain, Waste and Vent for Roofers, Framers and HVAC Techs