Orenco Effluent Pump Float Fault Tree

Why this matters

An Orenco effluent pump that runs continuously, never runs, or short-cycles is almost always a float or control problem before it is a motor problem. On a Biotube pump vault the floats are the only sensor the panel has, so a stuck, fouled, or miswired float makes a good pump look dead or floods the drainfield. Misdiagnosing the float as a failed pump wastes a pump pull, and missing a real high-water condition lets effluent back up or surface at the dispersal field. Work the floats in a defined order, with a meter and a known-good reference, and you reach the actual fault without guessing.

Orenco timed-dose and demand-dose panels (VeriComm, MVP, S1 simplex) share the same float logic: a redundant-off (low) level, an enable/on level, and a high-water alarm. Get the float order and panel mode right and the rest of the tree falls out.

Symptom presentation

Three failure shapes cover most calls.

• Pump never runs, no alarm. Tank level is high but the panel shows no demand and the pump does not energize on manual override.
• Pump runs continuously or pumps the vault dry and air-locks (rapid cycling or running against a dry vault).
• High-water alarm active, pump may or may not be running. Red light and buzzer, effluent near the inlet invert.

Note whether the panel is timed-dose (pump runs on a timer enabled by a float band) or demand-dose (on float starts, off float stops). The float you suspect changes with the mode.

Quick checks

Before pulling anything:

1. Confirm power. Verify 120/240 VAC at the panel breakers and that the GFCI or breaker has not tripped. Panels feed the pump through a contactor or relay; a tripped breaker reads as a dead pump.
2. Read the event counter and elapsed-time meter. VeriComm/MVP panels log dose counts and runtime. Zero recent doses with a high level points to a control or enable-float fault; thousands of short doses point to a stuck-on or chattering float.
3. Manual override. If the pump moves water on manual (Hand) but not on Auto, the motor and check valve are fine and the fault is in the float or control logic.
4. Open the riser and look. Effluent level relative to the bracket tells you which band the water is in. Note any rag, grease cap, or biomat fouling the floats.

Isolation tree

Work the floats from the panel back, pump breaker locked out for any wiring step.

Step 1 - Identify the float set and mode. Orenco mechanical floats (MF series) are normally-open or normally-closed mercury-free tilt switches. A demand-dose simplex typically has three: redundant-off (lowest), on (middle), high-water alarm (top); timed-dose has an enable band plus the alarm float. Map the float bracket positions to the panel terminals before testing.

Step 2 - Ohm each float at the panel. Disconnect the float pair at the terminal strip. With the float hanging down (low) and then tipped up (high), read continuity:

• A normally-open float reads open hanging, closed tipped up.
• A normally-closed float reads closed hanging, open tipped up.

A float that reads the same in both positions, or a partial resistance instead of a clean open/closed, is failed. Float cables also fail at the strain-relief grommet; flex the cable while metering and watch for an intermittent reading.

Step 3 - Branch on symptom.

Pump never runs, no alarm:

• Enable/on float stuck open (NO float never closing). Lift the float by hand at the riser; if the pump starts, the float is fouled or stuck low. Clean or replace.
• If lifting does not start the pump, jumper the on-float terminals at the panel. Pump starts: float or cable bad. Pump still dead: control fault (relay, contactor, timer board, or VeriComm float input) - check the panel's float-input LEDs.

Pump runs continuously / pumps dry:

• Off float (or redundant-off) stuck closed, never telling the pump to stop. Lift and drop it; if the pump does not stop, jumper-open the off terminals. Pump stops: off float failed closed. Pump still runs: contactor welded closed or relay stuck - replace the contactor.
• On timed-dose, continuous running with the timer counting normally usually means the enable float is stuck on with the off/redundant float also fouled. Verify both bands.

High-water alarm active:

• Alarm float reads closed (tipped) with water actually below it: float stuck up on a rag or the bracket. Free it; alarm clears.
• Alarm float closed with water genuinely high and pump not dosing: the real backup case. Confirm the on float is calling and manual run moves water. If manual run does not move water with a healthy pump, suspect a clogged Biotube screen, closed ball valve, or seized check - not a float.

Step 4 - Confirm the pump only after floats clear. Megohm the windings (>1 megohm to ground) and read running amps against the nameplate (Orenco PF/OSI pumps list FLA). Amps high with low flow = restriction; amps zero with voltage present = open winding.

Confirming diagnosis

You have isolated the fault when one of these holds:

• The suspect float ohms out wrong in one position and a known-good float restores correct pump behavior, or
• A jumper at the float terminals reproduces the missing pump action (proving the float, not the control), or
• Manual override moves water while Auto does not (proving control/float, not pump/hydraulics).

Re-run one full dose cycle on Auto: the level drops to the off band and stops, then refills to the on band and starts, with the dose count incrementing once per cycle.

Remediation

• Replace failed floats with the matching Orenco MF normally-open or normally-closed unit; set bracket band heights per the installer's level sheet so dose volume and redundant-off clearance are preserved.
• Clean fouled floats and the Biotube vault screen; reseat the float stem so cords cannot tangle.
• Re-terminate cracked float cables at the strain relief or splice with a watertight, listed connector - never a wire nut sitting in effluent.
• Replace a welded contactor or a relay that failed to release.
• After any float move, verify redundant-off keeps the pump submerged (no air-lock) and the alarm float trips above the on band. Record dose count, runtime, and amps as a baseline.

References

• Orenco Systems, "PF Series Effluent Pump Installation and Operation Manual" (NIB-PF) and "Control Panel Installation and Operation" manuals (VeriComm/MVP) - float-level and terminal-strip wiring.
• Orenco Systems, "Biotube Pump Package Installation Instructions" - float bracket and screen-vault setup.
• NSF/ANSI 40, Residential Wastewater Treatment Systems - ATU performance and alarm requirements.
• U.S. EPA, "Onsite Wastewater Treatment Systems Manual" (EPA/625/R-00/008) - pump and dosing-control guidance.
• Applicable state onsite wastewater code for alarm, dosing, and float-set installation standards.