Grinders, also called low pressure sewers, were originally developed to help homeowners who add additional bathrooms to their structures. When gravity cannot move the waste from the add-on bathroom, a macerating pump inside a small tank operates like a garbage disposer. It is used to grind waste into liquid form and move it into the already existing sewer line or septic system. Grinders were intended for secondary use, not the primary waste removal of a residence.
More recently, counties and cities are using grinders to chain-link whole neighborhoods to a municipal sewer system. Municipalities like them because they can install grinders for approximately one-half the cost of gravity-fed, traditional sewers and with much less disruption to the neighborhood. The installations require lateral drilling of small diameter pipes to connect to existing nearby sewer lines. Lift stations may still be necessary in neighborhoods with high density or difficult topography. The grinders are handling heavy waste, the direct outflow of toilets.
A grinder sewer system consists of a small tank capable of holding approximately 250 gallons (capacity varies with models) of water and sewage. For the average home, this is a one-day capacity of waste and water usage. Grinders use a submersible macerating pump, several floats to trigger the pump out action, relays to manage the starting and stopping of a 2+ horsepower motor, alarms, warning lights and override switches, and the very important mechanical check valve to stop waste from backing up into your home. While the grinder does not run constantly, the small capacity and the lack of override on the pump means you may not know how much capacity you have when the power goes off. The design requires continuous use and requires a cleanout action and filling of water when left unattended for long periods of time such as vacation or seasonal use.
The average grinder is a very complex mechanism that operates in a highly corrosive, raw waste environment. Average life expectancy of a grinder pump is 3-5 years. Even when there is power, these components are known to have high maintenance requirements, especially if high-quality materials like stainless steel have not been used throughout. Without power, pressurized sewers are totally dependent upon the check valve system that keeps the backflow out of homes. During Irma, a city in south Florida with high percentage of grinders experienced widespread damage and human tragedy as a result of non-functional grinders and lift stations. You can see if this is a concern for your area by linking to the article.
To understand more about the complexity of a grinder, here are several videos to give you a pictorial view. Below is a video of a service technician fixing a homeowner’s 2-year old grinder. The homeowner’s repair cost was $1,000. Note in the video the following: 1) electrical errors were made with the original installation yet still passed by an inspector, (2) buildup of grease and residue inside the pump, (3) corrosion evident after only 2 years of use. Repair Video
The next video on YouTube is of a contractor explaining the grinder system.
HEALTH and HOME RISKS: GRINDERS ARE CALLED SEWERS, BUT PRESENT UNIQUE CHALLENGES AND RISKS TO INDIVIDUAL HOMEOWNERS THAT DO NOT EXIST WITH A TRADITIONAL GRAVITY FED SEWER.
- Homeowners insurance does not cover sewer back-ups whether the cause of the back-up is your grinder or your neighbor’s. A special insurance rider must be purchased to protect your home and its contents.
- Grinders do not remove solids; they pulverize them and push them into small diameter sewer feeder lines. It is a toxic slurry full of fats, grease, and human waste that can form a blockage anywhere in the transport scheme. If the check valve is working, the backup will occur in your yard, not in your home, but that exposes you and your family to the same bacteria and toxins people are exposed to when a gravity sewer line is blocked and sewage flows out a manhole onto the streets or into yards. Raw sewage is classified as a biohazard.
- A grinder’s small tank size limits your options when power is interrupted. You may have 24 hours before you must evacuate, or you may have much less than that depending on the last time the grinder emptied itself into the feeder line. While some cities offer a pump out service in emergencies, large scale installations of grinders can make this an overwhelming task and an unreliable plan in cases of wide scale, prolonged power outages.
- While generators can provide temporary power, generators themselves present their own safety challenges and will not help the homeowner if lift stations are also not operating.
- Substances that will damage your grinder include: cooking fat, lard, oil, grease, degreasing solvents, cigarette butts, dental floss, sanitary napkins, tampons, diapers, Q-tips, sanitary wipes or disposable floor wipes, hair clippings, cat litter, strong chemical, toxic, caustic or poisonous substance, explosive or flammable materials, glass, metal, wood, eggshells, seafood shells, coffee beans, aquarium rocks or gravel, plastic objects, rubber gloves, fireplace ashes. Any hard item discarded into a toilet is enough to damage the grinder pump.
- You cannot not allow water to pool around the grinder’s ground level breathing vent. The grinder will not operate if water enters this vent. Unlike sewers that use roof level venting, grinders vent at ground level. You will have odors in your neighborhood with grinders.
To summarize, any subdivision offered the opportunity to replace septic systems with grinder sewers should really think twice. They were never meant to replace gravity fed sewer systems. One of your greatest concerns should be whether a municipality or county requires full transparency on real-estate transactions. In the State of Florida, sellers are required to disclose whether they have a sewer or septic system. Brace yourself for a very upset buyer who finds out they have an electro-mechanical sewer and they did not purchase the correct homeowner policy rider.