Sewage pump (C) Daniel Friedman Septic / Sewage Grinder Pump Damage Diagnosis & Repair
Avoid Damage to Sewage Pumps, Septic Pumps, and Grinder Pumps & How to Fix Sewage Grinders

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Sewage & septic pump clog or failure causes, diagnosis, repair, prevention guide:

This article describes the causes of and steps to prevent clogging and/or damage to septic pumps, grinder pumps, and sewage ejector pumps. We include excerpts from sewage or septic grinder pump manufacturers' installation manuals that describe sewage pump diagnosis & repair procedures.

This article series also lists septic and grinder pump types, brands, and will identify pumps that are resistant to damage from debris or objects that may enter the toilet, sewer line, or septic tank.

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Septic Grinder Pumps, Sewage Ejector Pumps: Causes of Clogging Failures

Sketch of a common sewage grinder pump used in a modern basement readers report troubles with several types of septic pumps, sewage pumps, and grinder pumps, both for sewage ejector pumps located in the home (such as to pump a basement toilet waste line up to a higher main drain) and for pumps that operate septic or graywater tanks.

Septic pump damage may occur from certain objects that enter building drains regardless of where and how the pump is used, including in-building sewage ejector pumps (shown at left) or pumps used in septic tanks or septic effluent tanks.

Some of the items in this list won't damage the septic tank itself as their volume is small and they don't usually block the septic piping or baffles, but if your septic system or even public sewer connection use a septic pump, grinder pump, or sewage ejector pump, the items listed here can clog and damage or even destroy a sewage pump, leading to costly repairs.

Article Series Contents

Watch out for the following conditions that cause clogging and even burnup of various types of sewage pumps, grinder pumps, ejector pumps, and septic pumps:

Don't Flush These Items Down the Toilet - They Clog or Burn Up the Grinder Pump

Sketch of a common sewage grinder pump used in a modern basement

See WHAT CAN GO INTO TOILETS & DRAINS? for complete details.

Septic & Sewage Pump Damage & Repair Procedures

The following sewage pump (septic grinder pump) diagnosis & repair advice is adapted from installation manuals from manufcturers & from other sources. See REFERENCES at the end of this article.

Table of Septic or Sewage Pump Diagnostic Steps

Grinder Pump Problem Probable Cause  Comments
Sewage / Grinder Pump Motor will not start or won't keep running
  • Pump circuit power switch is off
  • Pump float switch stuck
  • Pump float switch not properly set vs. waste level in the pump basin
  • Pump float switch has failed
  • Blown fuse, tripped circuit breaker
  • Pump motor overload / reset button tripped
  • Pump grinder / impeller seized from debris, or is broken, loose, damaged
  • Pump grinder seal is damaged
  • Pump motor start / run capacitor failed
  • Pump wiring is damaged or has come disconnected
  • Low voltage on the pump circuit




Sewage / Grinder Pump Motor trips circuit breaker, blows fuse, overheats
  • Low voltage on the pump circuit
  • Pump grinder / impeller seized from debris, or is broken, loose, damaged
  • Pump discharge blocked, stuck check valve
  • Internal short in pump motor or pump motor capacitor
Sewage / Grinder Pump Motor short cycling, rapid on-off or too-frequent cycling
  • Pumping chamber, well, pit is too small
  • Pump float switch is sticking or jamming
  • No check valve installed on pump discharge line
  • Check valve installed too far from pump
  • Other damage to the pump float switch or switch electrical components
The pumping chamber or basin and the pump's pumping capacity must be adequate to handle the maximum anticipated wastewater flow-rate into the system
Sewage / Grinder Pump Motor won't stop running
  • Pump float switch is sticking or jamming in the ON position
  • Other damage to the pump float switch or switch electrical components (fused contacts)
Weak pump output flow rate or pump runs but no water output
  • Clogged pump strainer housing not admitting water inflow to the grinder
  • Clogged discharge pipe
  • Clogged or stuck check valve or check valve vent opening (if present)
  • Pump discharge line routed higher than the pump's lift capacity
  • Low electrical voltage to the pump circuit
  • Pump motor running backwards
  • Air in the pumping basin from air in inflowing water

See Note 2 below


Reduced pump lift capacity or flow rate
  • Clogging in discharge piping ("increased pipe friction")
  • Clogging pump discharge line check valve
  • Pump impeller damaged by abrasives, chemicals, sand, improper cleaning & sharpening (grinder pumps)
See Note 2 below


  2. Vent opening at check valve: Zoeller Pump provides a combined union/check valve, the "Unicheck". The company notes that with this valve is installed, the installer must drill a 3/16" (5mm) vent opening in the discharge line at a height even with the top of the pump. This discharge line must be cleaned periodically. You should see water squirting out of this opening when the pump is running.
  3. Zoeller Pump Company, "Installation & Service Instructions, 803/805/807 Grinder Pumps", [PDF] Zoeller Pump Co., P.O. BOX 16347 • Louisville, KY 40256-0347, Website: Retrieved 2016/04/05, original source:
  4. Zoeller Pump Company, "Installation Instructions, Recommended Models, Effluent/Sump/DeWatering & Sewage[pumps]", [PDF] Zoeller Pump Co., P.O. BOX 16347 • Louisville, KY 40256-0347, Website: Retrieved 2016/04/05, original source:
    See to find the Authorized Service Station in your area.

Question: why is my septic pump using too much electricity?

i don't like the idea of these sewer ejection pumps as they suck electricity, i feel my builder dug the foundation too deep and therefore stuck me with this annoyance on my new home. it seems to be not working right now after 8months i am an was not pleased to find out this had to be used as i was not told of it until it was put in already. sucks electricity and whatever else. - Dave

Reply: check your septic pump float controls and check pump motor current draw

Sewage pump float switch schematic

Dave you can figure out just how much electricity your ejector pump is using either by some careful examining of the electric meter itself or by looking up the specs on your motor.

Normally these motors run only intermittently. I'd be surprised if the ejector pump was using as much overall electricity in watt-hours as your refrigerator, freezer, or air conditioner.

But if your actual tests and measurements show that it is a big electricity user, I'd check the current draw using an ammeter to see if the motor is within spec. A bad or failing motor can draw excessive current, or if a control is not working properly and the motor is running constantly that also would be worth fixing.

The septic pump float switch at left describes a common sewage pump control method used on Little Giant™ and many other submersible sewage grinder pumps.

This type of sewage pump float switch, also used on lots of sump pumps, swings in an arc between its high and low positions. It's a simple, reliable electric switch, but debris in the holding tank or improper tethering can lead to switch jamming.

Note that by moving the tether position of the float wire in the pumping chamber you can adjust the pump cut-in and cut-out wastewater levels in the holding tank. Sketch courtesy of [4]

Question: Our sewage ejector pump won't turn off - how do we fix it?

Our enjector sewage pump will not shut off even when there is nothing going into it - what do we do to fix this? Heather.

Reply: Check for and free up a stuck float switch or replace a failed ejector pump float control switch

Zoeller sewage pump

Heather, sewage ejector pumps normally are operated by a float control switch. As wastewater rises in the holding tank when the level is high enough the float switch turns the pump on. The pump runs until the level of wastewater falls enough to cause the float to fall far enough for the switch to turn off the pump.

So if your sewage pump never turns off, presuming it's properly wired, the float switch is either stuck on debris in the holding tank, or the switch needs to be replaced.

The image at left shows the second very commonly-used type of float control switch, in this case using Zoeller™ pumps as an example.

The red arrow indicates the actual float - on occasion a float may become waterlogged or simply disconnected from its mounting shaft. The green arrow in our sewer pump float switch example is the actual switch assembly that turns the motor on and off as the float, on its shaft, rises and falls vertically. Image source: [4]

Take a look at the two most common sewage float switch types in our Little Giant™ sketch above and the Zoeller™ sewage pump and control switch image at left. Your switch probably looks like one of these two types.

In a few rare instances I have found homes at which the ejector pump float switch had failed and the owners, rather than replacing the switch, just hard-wired the pump to turn on and off by a manual switch. This is a bad idea for obvious reasons including inconvenience and the risk that either the pump is left on longer than necessary or left off leading to a sewage backup.

To diagnose the sewage pump control problem it's best to open an inspection port on the holding tank where the ejector pump is located. It may be possible to spot and remove a object clogging the float switch. Otherwise replacing the float switch is the next step.

Little Giant Remote float switch

Watch out: in addition to obvious bacterial hazards at sewage pumping stations there are methane gas hazards of explosion and asphyxiation - don't work alone. Also see our list above of things that can clog up or damage a sewage ejector pump.

Is your sewage ejector pump already damaged? Maybe not. Some sewage pump models indicate in the installation and maintenance manual that the pump can tolerate being run "dry". But best practice is to set the float control switch so that the liquid level does not drop below the pump body.

Other sewage grinder pump and ejector pump control switches are illustrated here.

The float and tube type remote float control switch (left) is used on some sewage pumps and sump pump systems.

This switch and and float assembly is also very similar to a mechanical float and switch found as well in water softener brine tanks to control the water level in the tank.

The float moves vertically up and down in a plastic tube. The tube helps protect the float from jam-ups due to debris in the wastewater tank.

Image source: [5]

Little Giant Remote float switch

The Little Giant™ remote float control switch (left) can be used as an auxiliary control / warning device on sewage and sump pump ejector installations to control an alarm.

By mounting this switch at an activation position higher than the normal float switch that controls pump operation, this remote control switch can activate a light or audible alarm to warn building occupants that the sewage system is not being emptied.

Image source: [5]

See SEWAGE PUMPS for more guidance about buying, installing, and adjusting the controls on sewage grinder pumps and sewage ejector pumps.

Question: what is the white waxy stuff that caused my septic pump float swith to stick & clog up leading to failure of my septic pump?

What do you suppose was the large white waxy clumpy substance that I found recently in my septic pump container? The sticky substance was stuck to the sides of the tank (where it was several inches thick). It was also stuck all over the septic pump, and stuck all over the float switch.which of course was the problem and the reason for opening the tank. This accumulation happened over 2 years and 5 months.
thanks. - Rani 8/11/11



We're not sure - you could send a sample to our forensic lab for free analysis. But a good guess is that your sewage ejector tank or septic tank that uses a septic pump was clogged by someone who used too much powdered detergents in a clothes washer or dishwasher.

It's well estblished that using excessive amounts of powdered detergent in a dishwasher or clothes washer can lead to accumulation of a gooey mess that clogs drains or even septic drainfields. Now hou have provided another important example: excessive detergent use OR using a budget detergent that contains large amounts of clay fillers can clog the pump float control switch or the pump intake in a sewage ejector pump or sewer pump as well.

We discuss detergent choices & recommendations to minimize drain and septic problems in two locations.

Please see


also see Dishwasher & Laundry Detergents Containing Phosphates & Surfactants for a discussion of the effects of phosphates & detergents on the environment.

This is part of our article series on sewage pumps that begins at SEPTIC SYSTEM PUMPS.

Question: toilet paper clogged our Zoeller grinder lift pump

Zoeller Shark series sewage grinder pumps models 803/805/807 main parts (C) adapted

[Click to enlarge any image] Above, main parts of a sewage grinder pump, adapted from Zoeller's Shark series 803-805-807.

2016/04/05 Thomas Guastavino said:

We have a Zoelner grinder lift pump that recently clogged with toilet paper when to wrapped around the impeller. Are there any recomendations for what type of TP is best to prevent these types of problems?


Thomas I've been testing toilet paper breakdown rates for almost a decade - one experiment is long-going; my OPINION is that all toilet papers break down just fine in a septic tank itself - changing the paper brand won't reliably fix the problem you encountered.

The grinder pump is going to run before most toilet papers will have separated into small fragments.

So I suspect there's a different problem: the grinder - tampons, or some other stuff can clog up sewage pumps. (Dental floss is one of the worst offenders and it's hard to keep that out of the pump). But Zoeller indicates quite clearly that their residential sewage grinder pumps, such as the Zoellr Shark 803/805/807 Residential Grinders can handle "all flushable wastes" - to me that means feces and toilet paper but not tampons and probably not dental floss.

Are we sure you have the right pump type and model installed. Sometimes people install a de-watering sump pump or a simple effluent lift pump where a grinder pump is needed.

If you have the right type and model of pump installed, check the pump inlet openings to be sure that there is no damage there.

Zoeller's sewer pump instructions also point out that a role of the pump chamber cover is to prevent debris from entering the pumping chamber from that direction as well.

Zoeller can be reached at

Zoeller Pumps
3649 Cane Run Rd.
Louisville, KY USA 40211

Phone: +1-800-928-7867
Phone: +1-502-778-2731
Fax: +1-502-774-3624
Email for Product Support:

BUT NOTE that the company says
If you are a homeowner, please contact your local Representative with questions.


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