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A grinder pump is a waste management device. Waste from water-using household appliances (toilets, bathtubs, washing machines, etc.) flows through the home’s pipes into the grinder pump’s holding tank. Once the waste inside the tank reaches a specific level, the pump will turn on, grind the waste into a fine slurry, and pump it to the central sewer system.
Grinder pumps can be installed in the basement or in the yard. If installed in the yard, the holding tank must be buried deep enough that the pump and sewage pipes are below the frost line.
There are two types of grinder pumps, semi-positive displacement (SPD) and centrifugal.
The grinder pump “station” consists of the pump, a tank, and an alarm panel. A pump for household use is usually 1 hp, 1.5 hp or 2 hp. A cutting mechanism macerates waste and grinds items that are not normally found in sewage, but may get flushed down the toilet. The pump has a level sensor either built into the pump, called “sensing bells,” or attached externally to the pump, called “floats.” (The level sensing devices vary among grinder pump manufacturers.)
If the pump malfunctions and the waste level in the holding tank rises above a certain level, the alarm panel should alert the homeowner that the pump is experiencing problems. The alarm panel should have both a buzzer and an indicator light.
The holding tank, likely constructed of fiberglass, high-density polyethylene (HDPE) or fiberglass-reinforced polyester (FRP), has an inlet opening and a discharge opening. The pipes from the home are connected to the inlet; the pipe that leads to the sewer main is connected to the discharge. Often, more than one home or restroom (in a park, for example) can be connected to one grinder pump station. In this case, more than one inlet can be installed. It is a good idea to consult the manufacturer or factory representative before purchasing a grinder pump station to ensure that more than one inlet hole can be drilled.
The tank has a lid made from heavy-duty plastic or metal that is bolted and/or padlocked shut to prevent entry by unauthorized persons.
Grinder pumps should not require preventive maintenance. However, grinder pumps that use floats to sense the level in the holding tank are prone to grease buildup that may turn the pump on unnecessarily, or not turn on the pump at all, causing the tank to fill up and sewage to possibly back up into the home or yard. To prevent this, grinder pumps that use floats are often hosed down to remove the grease from the floats.
Homeowners are not usually limited by what they can or can not pour down their drains because their home has a grinder pump. Sanitary napkins, diapers, kitty litter, paint, oil (both motor oil and cooking oils), etc. should not be flushed or poured down any drain, whether the home is connected to a gravity sewer system, septic tank, grinder pump or cesspool.
A questionable item is "disposable wipes" that are made by cleaning companies for personal use, cleaning toilets, etc. Some wipe companies say "flush one at a time," some say "not for pump systems," some say "safe for sewers." Check with the grinder pump manufacturer for their recommendation. Even though a wipe company says their product can be flushed, chances are, they don't have a grinder pump. The wipes, if they don't dissolve in water or don't dissolve quickly, can collect in the basin. They will likely ball up in the tank, and then a massive "wipe ball" will get into the pump and jam it. In larger sewage pump stations the clogging problems are often solved by installing a chopper pump in the tank. A chopper pump is able to handle larger/tougher solids than a grinder pump, including hair balls, diapers, sanitary napkins, cloting, etc.
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Service and Repair Edit
Self-repair is not recommended. Contact the sewer district or the grinder pump manufacturer, who should refer you to an authorized service dealer, for repair. If calling a plumber, ask if they have been trained to repair the specific grinder pump in question. Otherwise, you may end up paying for unnecessary repairs or even a complete replacement.