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Dirty jobs, done like a gentleman.

Check valve and anti-siphon valve repair

The grinder pump check valve is a one-way flap on the discharge that keeps sewage from running back into the tank when the pump stops; the anti-siphon valve beside it keeps the pressure main from pulling the tank dry. When either fails, the pump cycles without reason, runs without pumping, or floods the tank from the street side. Grinder Pump Gents repairs and replaces check valves and anti-siphon valves on grinder stations and sewage ejector systems across Baldwin and Mobile counties.

This is one of the few parts the utilities write into their rules by name, so the right valve in the right place is part of the job.

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Engraving of a gentleman in a top hat and monocle holding a brass check valve up to the light, as a jeweller would a diamond.

Plate X. Appraised as a diamond. Worth rather more to the household.

Why the utilities care about this valve

Gulf Shores Utilities requires a check valve and anti-siphon device on every grinder system's discharge piping. The City of Orange Beach code puts them within two feet of the top of the tank. E-One requires its own stainless steel Uni-Lateral check valve between the station and the street main, in addition to the check valve and anti-siphon valve built into the pump core. Liberty's Omnivore manual asks installers on pressure sewers to confirm a redundant check valve assembly, a curb stop and check valve, between the pump discharge and the street main, placed as near the right-of-way as it can be. Riviera's customer side begins at the property-line shut-off and check valve. On a shared pressure main, a failed check valve at one house lets the neighbors' flow push into that house's tank.

How a failed check valve shows up

The manufacturers' troubleshooting tables point at the check valve for three symptoms.

  • The pump starts and stops too often with nothing draining: Liberty lists a leaking check valve, Zoeller a check valve stuck or missing, and Keen a check valve stuck or installed backwards.
  • The pump runs but the level does not drop: Keen, Liberty and Myers all list a check valve stuck closed or installed backwards, alongside air lock and a closed valve at the street.
  • Water runs back into the tank after each cycle, heard as a rush at the inlet, or a tank that refills faster than the house can explain.

What we check, and what you should leave alone

The valve is checked with the pump running and stopped: whether the flap seats, whether flow reverses, whether the anti-siphon device opens, and whether the valve was installed with its arrow pointing away from the tank, which Zoeller's instructions make a point of. On a station where the valve sits in a small vault at the property line, the vault is pumped down to reach it. E-One's owner guide tells homeowners plainly not to touch the valves, and there is a good reason: the main side of a check valve on a shared pressure sewer is under the neighbors' pressure.

Ejector pump check valves

Indoor sewage ejector systems need the same part. The residential code adopted in Alabama requires a check valve and a full-open valve on the discharge of a sewage ejector, and Zoeller's instructions call for the check valve's arrow to point away from the basin. Liberty's sewage pump table lists a pump that runs periodically with no water being used as a check valve problem. The repair is the same: confirm the flap, confirm the direction, replace the valve if it will not seat.

Where this work is allowed

On every owner-maintained system in both counties, because a valve is a repair item: MAWSS in Mobile County, and in Baldwin County BCSS, Gulf Shores Utilities, Orange Beach, Riviera's Foley system, Fairhope, Daphne, Loxley and North Baldwin. Riviera's handbook names valves among the customer's responsibilities. Where the utility maintains the pump, SAU, MCWS and MAWSS decentralized subdivisions, it maintains the valves too.

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Sewage backing up or overflowing? Stop using water and call now: (251) 850-8031. On a utility-owned pump, call your utility first.

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How the visit goes

  1. Step 1: Confirm the symptom

    Short cycling, running without pumping, or backflow each point at the valve in a different way.

  2. Step 2: Isolate the valve

    Pump stopped, discharge isolated where a shut-off exists, vault pumped down if the valve is at the property line.

  3. Step 3: Inspect flap, seat and direction

    Flap condition, seating, debris, and the flow arrow checked; the anti-siphon device tested.

  4. Step 4: Repair or replace

    Flap or valve replaced with a valve that meets the utility's requirement and the pump maker's instruction.

  5. Step 5: Prove it

    Pump run through a cycle with the valve watched for backflow and the cycle timed.

Check who can do the work

Your sewer utility decides who can repair or replace the pump. Compare the rules by utility before scheduling the work.

Questions people ask

What does an anti-siphon valve do on a grinder pump?

It lets air into the discharge after the pump stops so the pressure main cannot siphon the tank below the pump's off level. Without it the pump can run dry or the floats can be left hanging in an empty tank. Gulf Shores Utilities and Orange Beach both require one.

Can a check valve be installed backwards?

Yes, and the manuals list it as a cause of a pump that runs but moves nothing. Zoeller's instructions say the arrow on the valve must point away from the basin. We check direction before anything else.

Do sewage ejector pumps have a check valve?

Yes. The residential plumbing code requires a check valve and a full-open shutoff on an ejector's discharge, and the same cycling and backflow symptoms apply. Zoeller sells the check valve separately from its ejector packages, so an older system may be missing one.

The pump cycles every few minutes at night when nobody is using water. Is that the check valve?

Often. A leaking check valve lets the discharge pipe drain back into the tank, which refills it to the on level. Keen, Liberty and Zoeller all list it. The other suspects are a leaking fixture in the house, ground water entering the basin, and a float set wrong.

Sources and facts

  1. GSU: grinder systems shall be equipped with a check valve and anti-siphon device on the discharge piping. Orange Beach: check valve and anti-siphon within 2 ft of the tank top. Gulf Shores Utilities, Grinder Pump Specifications, www.gulfshoresutilities.com/grinder-specs; City of Orange Beach Code of Ordinances Sec. 74-36 and 74-51, library.municode.com/… (read 2026-11-04)
  2. E-One requires the Uni-Lateral stainless check valve between the station and the street main; the core has an integral check valve and anti-siphon valve. E/One DH071 Drawings, Universal Wet Well (NA0050P01 Rev E), eone.com/… p.1; E/One Product Family brochure (LM000365 Rev D), eone.com/… p.2 (read 2026-11-04)
  3. Liberty: on pressure sewer applications verify a redundant check valve assembly (curb stop and check valve) between pump discharge and street main, as close to the right-of-way as possible. Liberty Pumps Installation Manual 5647000N, Omnivore 2 hp Grinder Pumps, www.libertypumps.com/… p.1 (read 2026-11-04)
  4. Riviera: the customer is responsible for the connection to the customer's side of the shut-off valve and the whole system on that side, including valves. Riviera Utilities, Sewer Policy Handbook sections 7.3-7.4 (file dated 2024-05), www.rivierautilities.com/… (read 2026-11-04)
  5. Short cycling: Liberty lists a leaking check valve; Zoeller a check valve stuck or missing; Keen a check valve stuck closed or backwards, ground water, leaking fixtures, floats moved. Liberty Pumps Installation Manual 2399000E, ProVore 1 HP Residential Grinder Pumps, www.libertypumps.com/… p.11; Zoeller FM2903 Installation and Service Instructions, 803/805/807 Grinder Pumps, zoellerpumps.com/… p.2; Keen Pump O&M-KPCG, 1 HP Progressive Cavity Submersible Grinder Sewage Pumps, keenpump.com/… p.9 (read 2026-11-04)
  6. Runs but no pumping: Keen (air lock, valves clogged or closed), Liberty (check valve stuck or backwards, valve closed, head too high), Myers (check valve flapper stuck, valve at street off or redundant check valve backwards). Keen Pump O&M-KPCG, 1 HP Progressive Cavity Submersible Grinder Sewage Pumps, keenpump.com/… p.9; Liberty Pumps Installation Manual 2399000E, ProVore 1 HP Residential Grinder Pumps, www.libertypumps.com/… p.10; Pentair Myers Owner's Manual 23833A744, 2 HP Submersible Sewage Grinder Pump WG20/WGX20, www.pentair.com/… p.8 (read 2026-11-04)
  7. Zoeller: check valve arrow points away from the basin; check valve sold separately on 912 ejector systems. Zoeller pre-plumbed sewage system instructions, zoellerathome.com/…; Zoeller 912 residential sewage ejector systems manual, manuals.plus/… (read 2026-11-04)
  8. E-One: do not touch the valves. E/One Owners Guide (LM000403 Rev G), eone.com/… p.4 (read 2026-11-04)
  9. IRC P3007: sewage ejector discharge requires a check valve and a full-open valve; adopted for Alabama residential plumbing by rule 720-X-1-.02. 2021 International Residential Code, Section P3007 Sumps and Ejectors (text via up.codes), up.codes/…; Alabama Plumbers and Gas Fitters Examining Board rule 720-X-1-.02 (2021 IRC adopted for residential plumbing), admincode.legislature.state.al.us/… (read 2026-11-04)
  10. Liberty sewage pumps: runs periodically without water being used points to the check valve. Liberty Pumps P380/P680 sewage pump manual 1167000A, www.libertypumps.com/… (read 2026-11-04)

Related

  1. Grinder Pump Running But Not Pumping: Air Lock and More
  2. Grinder Pump Alarm Keeps Going Off? Why It Returns
  3. Grinder Pump Noise: Humming, Rattling and Grinding Sounds
  4. Why Is My Grinder Pump Running Constantly? 7 Causes
  5. Grinder Pump Float Switch and Level Sensor Repair
  6. Grinder Pump Discharge Line Repair (Pressure Service Line)
  7. Grinder Pump Repair in Baldwin & Mobile Counties, AL
  8. Who Owns Your Grinder Pump? Rules by Utility, Quoted

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