How do I replace a sewage ejector pump float switch?

Two symptoms point at the float: the pump will not start when the basin is full, or it starts and will not stop. Liberty Pumps' troubleshooting chart for its LE-series sewage pumps lists "Defective float switch" with the fix "Replace float switch" for both. But the same chart lists cheaper problems first. For a pump that does not start, it lists "Float switch unable to move to pump ON position due to interference in basin or other obstruction," with the fix "Position pump or float switch so that it has adequate clearance for free movement." It also lists "Insufficient liquid level," meaning the basin has not filled enough to lift the float.

For a pump that will not shut off, the chart lists "Float switch unable to move to pump OFF position due to interference with the side of basin or other obstruction." Zoeller's checklist says the same thing another way: the pump should be checked frequently for "debris and/or buildup which may interfere with the float" working properly. A float that is jammed against the wall or held down by debris can be freed without buying anything.

Air lock also makes a pump run without moving sewage, so see why a sewage ejector pump runs but does not pump before you blame the switch. And if the breaker keeps tripping, that is a different problem: why a sewage ejector pump keeps tripping the breaker.

That decides who should do the work. Liberty describes three arrangements:

• A plug-in switch on the pump. Liberty says its LE-Series automatic models come "factory-equipped with a float switch mounted to the pump." The switch cord has a piggyback plug, and "The purpose of this design is to allow temporary manual operation of the pump."
• A separate float and control panel. For pumps run by a panel or other optional control device, Liberty says to "follow the manufacturer's instructions provided with the control panel for power connections." Wiring a panel is an electrician's job.
• A pump wired directly into a control device or junction box. Liberty says "a certified electrician shall complete the wiring in accordance with the National Electric Code and applicable local codes."

If you are not sure which you have, look at the cord. A pump plugged into a piggyback plug in a wall outlet is the plug-in type. A cord that runs into a junction box or panel is the wired type, and that stays with a licensed electrician.

For a plug-in switch, the order below follows the manufacturer's own rules. It is not a substitute for your model's manual, so read it first.

1. 1Cut the power. Zoeller's instructions say: "Before servicing a pump, always shut off the main power breaker and then unplug the pump." Liberty adds: "IMPORTANT: Verify breaker is turned off before plugging in the switch."
2. 2Check the warranty. Liberty says "No repair work shall be carried out during the warranty period without prior factory approval." Doing it yourself can void coverage.
3. 3Do not lift by the cord. Liberty's safety list says "Do not lift or carry a pump or a float assembly by its power cord." Liberty's installation steps include a union just above the basin cover "to facilitate pump removal," which is where the pump comes out.
4. 4Do not enter the basin. Liberty says "Do not enter a pump basin after it has been used. Sewage and effluent can emit several gases that are poisonous." It also warns of "flammable and explosive gases," so no sparks and no live, exposed circuits near an open basin. Liberty says to "Wear adequate Personal Protective Equipment when working on pumps or piping that have been exposed to wastewater."
5. 5Do not splice. Liberty's warranty language excludes pumps where "the electrical cord has been cut, damaged, or spliced." A new float goes on with the manufacturer's part, not a spliced cord.
6. 6Set it up correctly. Liberty says the float "must have adequate clearance to side wall of basin and free, unobstructed movement throughout its complete travel and must not contact the pump, piping, or other objects." Also "Do not position the pump float directly under the inlet from drain tile or in the direct path of any incoming water."
7. 7Test. Liberty says to "Verify operation of the pump, floats, and alarm circuits" and "Run several cycles of water through the system to verify correct control operation for the installation."

The switch sets how full the basin gets before the pump starts, and how low it drains before it stops. Liberty's table lists factory settings by model, for example a turn-off level of 6 inches and a turn-on level of 14 inches for the LE50. It warns that the turn-off level "must be maintained as it is the minimum water depth to ensure proper cooling." A pump that runs below that level is not being cooled the way it was designed to be.

The top matters too. The 2024 International Plumbing Code says "The effluent level control shall be adjusted and maintained to at all times prevent the effluent in the sump from rising to within 2 inches (51 mm) of the invert of the gravity drain inlet into the sump." A float set too high leaves the basin too full.

Hire it out if the pump is wired into a panel or junction box, if the pump is under warranty, if you cannot get the pump out without standing in the basin, or if the float turns out not to be the cause. A plumber can pull the pump, replace the float assembly with the correct part, set the levels, and confirm the check valve and vent hole are working while the pump is out. An electrician should handle any panel or direct wiring.

Checking the float is also part of routine care. Liberty's quarterly list says to "Check for free and unobstructed float switch operation and float switch condition." Catching a sticky float early is much easier than replacing a failed one during a backup.

HQ Plumbing & Air is licensed and insured, and our residential plumbing service covers the plumbing side of this job. We give a free estimate, and you get the price up front before work starts. We take emergency calls 24/7, and if sewage is backing up, see what to do about sewage backing up into a tub or shower. For the bigger picture, sump pump vs ejector pump vs lift station explains how the three differ.