Maintenance of Grinder Pumps in Decentralized Wastewater Applications

October 11, 2019 | Blog, Wastewater

By: Roger Drews, Communities Unlimited

Grinder pumps and their use in decentralized wastewater applications are very prevalent in the United States.  Individual sewer treatment systems’ (septic tanks) capabilities are expanded with pump systems that apply treated water to lawns, instead of using potable water. This practice makes use of a second vessel, which is usually baffled to allow solids to settle, and a relative solids-free effluent is then pumped through sprinkler systems to water grass, flowers and shrubs. 

Grinder pumps in the 1/3- to 1/2-horsepower range are used to remove this water from the septic system.  Due to the relatively small size and minimal cost of these pumps, few preventative or predictive maintenance practices are available — or needed — to extend the life and performance of such units.

The initial cost of a pump for the dispersal system is usually less than $200. If it takes less than an hour to replace a pump that has stopped working, the maintenance cost remains the same as the initial cost, whereas hiring a maintenance mechanic charging $45 per hour would cost more to do a complete teardown, get worn-out parts replaced, rebuild the pump to working condition and still have an old pump in the system.  The life expectancy of a small grinder pump is three to five years because the pump does not run continuously and the environment is not very detrimental to the pump housing and electrical system. 

There are limited parts available anywhere to accommodate pump repair. Decentralized system operators should be prepared to do a quick change out whenever the pump fails.  Homeowners should purchase a spare pump after three years of service for the time the current one fails. With that practice, the average cost for the pump and its operation is less than $40 per year. Compared to a monthly average cost for wastewater services when hooked to a community system of approximately $45 per month, the small grinder system as part of a septic waste system is very economical. 

The economy of scale and cost per year can be even less if a homeowner carefully watches what they put down the drain.  Grease that gets into any wastewater collection or treatment system can cause grinder pumps to fail prematurely because it builds up in the grinder pump impeller and hardens over time.  The clogged impeller quits moving water down the natural path as the impeller is restricted in the water-handling capability with the reduced amount of water it can carry through it. The clogging effect usually causes the pump to overheat, which causes seal failure and requires pump replacement to accommodate repair. 

Most septic systems that have a sprinkler system as a part of the operation will give the owner several days’ notice before complete failure, whereas those systems without a pump system usually overflow before a problem is detected.  This overflow can cause a smelly environment in the basement of a home, and repairs and cleanup are much more complex.

Having the spare pump on-hand saves time later in ordering a new pump or driving somewhere to pick one up. Even when a pump mechanic responds to the emergency, having a pump unit on-hand will reduce the repair bill considerably.

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