High-Level Alarm After Rain: Pump Failure or Infiltration?
A 1,000-gallon two-compartment concrete tank serves a four-bedroom home. Its pump chamber has a high-level float alarm that sounded at 2:00 a.m. after 3 inches of rain. The homeowner silenced the alarm; by morning, toilets flushed slowly. The pump is a 1/2-hp submersible mounted on a 24-inch riser inside the chamber. The inspector finds the high-water float raised, the pump breaker on, and a scum line 6 inches above the normal pump-off float. With the selector switch in HAND, the pump hums but no water moves; the discharge pressure gauge downstream of the pump reads zero. The tank outlet baffle is intact. A check valve and a gate valve are fitted on the discharge line. The ground is saturated and the drainfield area has standing water in one low spot. The homeowner reports the alarm had never sounded before.
1. What is the most likely cause of the no-flow condition, and what checks would confirm it?
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The pump has power (breaker on, hum in HAND) but produces no pressure or flow. That points to a mechanical or hydraulic fault on the pump/discharge side, not to the rain alone. A high-level alarm means the pump did not move effluent at its normal on-float level, so the chamber filled. Confirm by checking pump amperage against nameplate: high amps with overload trip suggests a jammed impeller or seized bearing; normal or low amps with no pressure suggests a stuck-closed check valve or blocked discharge. Isolate safely by closing the gate valve, relieving pressure, and opening a union only if your protocol allows; otherwise defer to a septic contractor. Verify float sequencing by lifting floats or checking continuity, because a stuck on-float would also explain the high level. Do not attribute the problem to the saturated drainfield until the pump and discharge are proven functional. Report a pump/discharge fault, with drainfield loading as a separate concern.
2. What immediate safety and reporting actions should the inspector take?
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Treat the pump chamber as a confined space: never enter it, keep the lid secured when not being observed, use a four-gas meter, and stay upwind. Isolate electrical power before touching pump components, and do not open a check valve or union while the line may be pressurized. Keep the homeowner and pets away from the open chamber. In the report, separate observed facts from the likely cause: the alarm activated, the pump hummed without flow, pressure was zero, and the drainfield had standing water. State that the pump, floats, check valve, and discharge line require evaluation by a licensed septic contractor. Note that the homeowner silenced the alarm, which delayed response. Recommend water conservation until repairs are complete. Include a limitation that the cause was not fully determined because safe pump testing and discharge isolation were outside the inspection scope.
3. How should the report address the standing water over the drainfield?
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Standing water in a low spot after 3 inches of rain is not by itself proof of drainfield failure, but it is a hydraulic-loading concern. The report should describe the location, size, and odor, and distinguish it from the pump-chamber problem. If the pump failed, effluent may have backed up or the chamber may have overflowed, adding load. Recommend that the contractor evaluate the drainfield only after the pump is restored and the soil has drained. Advise the homeowner to divert roof and surface water, avoid driving over the area, and conserve water. If surfacing persists in dry weather, recommend a drainfield evaluation. Avoid concluding that the drainfield must be replaced based on one wet-weather observation.