Septic Pump Runs Constant After Control Panel Swap Decision Tree

Why this matters

You swap a failed control panel, restore power, and the effluent pump now runs continuously and will not shut off. A pump that never stops will run the tank dry, overheat, draw the field beyond capacity, and burn itself out fast. After a panel swap, a constant-run pump is almost always a wiring or float-logic mistake made during the swap, not a coincidentally failed pump. The new panel's relay/contactor may be miswired, the float leads may be landed on the wrong terminals, the float type may not match the panel's logic (normally-open vs normally-closed), or a manual/hand override got left on. This tree isolates the swap-induced fault quickly so you do not destroy the new pump.

Symptom presentation

The pump energizes and does not de-energize on its own; the tank draws down below the pump-off float yet the pump keeps running, or it never sees a float-off command. Note the panel's switch position (Hand/Off/Auto, or any manual override) and whether the constant-run started the moment the new panel was energized. A fault that appears immediately on the new panel's first power-up is a wiring/configuration error from the swap; a fault that appears later is more likely a float or contactor failure.

Quick checks

First, if the tank is running dry, kill power to protect the pump. Then, with LOTO for testing: confirm the panel HOA switch is in AUTO, not HAND (a panel left in HAND runs the pump constantly by design). Compare the new panel's wiring diagram to the as-wired terminals: verify pump leads, float leads, and neutrals/grounds land where the diagram specifies. Confirm float type matches panel logic (the panel expects either NO or NC floats; a mismatch inverts the logic so the pump runs when it should be off). Manually tip the pump-off/control floats and watch whether the panel de-energizes the pump. Check the contactor/relay: does it drop out when the float opens, or is it welded/stuck closed?

Isolation tree

Branch 1, HOA switch left in HAND or a manual override engaged: the panel is commanding constant run by design. Confirm by switch position. Return to AUTO and retest. Simplest and most common post-swap miss.

Branch 2, float leads landed on wrong terminals: the control float that should stop the pump is wired so its state is ignored or inverted. Confirm against the panel diagram. Re-land the float leads on the correct terminals per the new panel's schematic.

Branch 3, float type/logic mismatch: the new panel expects normally-open floats but the installed floats are normally-closed (or vice versa), so the pump-off command never reaches the panel. Confirm by ohming the float across its leads and comparing to what the panel logic requires. Replace floats to match, or select panel settings/jumpers for the float type if the panel supports it.

Branch 4, contactor/relay stuck closed: the panel commands off (float opens, control logic drops) but the pump still runs because the contactor contacts are welded or the relay is stuck. Confirm by verifying the coil de-energizes on float-off while line voltage still passes to the pump. Replace the contactor/relay.

Branch 5, float fouled in the up position: the control float is physically held up by debris or tangling, so it never signals off. Confirm by lifting/freeing the float and watching the pump stop. Re-rig the float clear of the pump and debris.

Branch 6, wide-angle versus narrow-angle float mismatch: some panels use a single wide-angle pump float that both starts and stops the pump across a large tilt range, while others use separate narrow-angle on and off floats. If the swap paired the new panel's logic with the wrong float style, the pump never sees a clean off command. Confirm by comparing the installed float type to the panel's required float configuration in the schematic. Install the float style the panel expects, or wire the existing floats to the panel's matching input terminals.

Confirming diagnosis

HAND-mode confirmed by switch position; fixed by returning to AUTO. Wiring error confirmed by terminals not matching the panel diagram. Float-logic mismatch confirmed by float ohm-state opposite to what the panel logic requires. Stuck contactor confirmed by the coil de-energizing on float-off while the pump still receives power. Fouled float confirmed by a float mechanically stuck up that, when freed, lets the pump stop. Because the fault appeared at the new panel's first energization, the wiring/logic branches are the highest-probability findings; record the panel diagram comparison as evidence.

Remediation

Return the HOA switch to AUTO and remove any override. Correct float and pump terminations to the panel schematic exactly. Match float type to panel logic or set the panel for the installed float type. Replace a welded contactor/relay. Free and re-rig a fouled float. After any fix, run a full cycle: confirm the pump starts at the pump-on level, draws the tank down, and stops cleanly at the pump-off level, with the alarm functioning. Verify amp draw against nameplate. Do not return the system to service until the pump cycles off on its own.

References

• U.S. EPA, Onsite Wastewater Treatment Systems Manual (EPA/625/R-00/008), pump controls and float logic.
• Manufacturer control-panel wiring diagrams and float-switch installation guides (Orenco, SJE-Rhombus, and equivalents) for NO/NC float logic.
• OSHA 29 CFR 1910.146, Permit-Required Confined Spaces, and lockout/tagout 29 CFR 1910.147.
• NSF/ANSI Standard 40 where the pump serves an aerobic treatment unit.
• State onsite-wastewater code requirements for pump panels, floats, and high-water alarms.