How do drugs affect an on-site septic system?

There’s an older home in the neighborhood that was occupied by a single woman for more than two decades. When she died of cancer a few years ago, her son inherited the home and moved in. Not long after, the septic system failed and had to be replaced.

Several people believe that the woman’s cancer medications, ingested and then flushed, helped to accelerate the septic system failure. Experts in the business say the drugs probably were not the only reason, especially if the same drain field had been used for many years.

“When a system fails, everybody wants to blame somebody,” said Eric Knopf, owner of Poulsbo-based Indigo Design Inc., a company that designs and maintains septic systems. “The truth is that a septic system – like just about everything else – has a life span. You can get about 30 years on a home’s roof. Some cars will get you 200,000 miles; some maybe 300,000. Septic systems also have a definite life span.”

Thousands of households use a soil absorption septic system to dispose of waste. A properly designed, installed and maintained septic system is comprised of a water-tight container, drain field and adequate soil conditions beneath the drain field. Only 32 percent of all septic systems in existence meet the criteria for adequate soil absorption, due to the presence of bedrock, sandy soil and high water tables.

Nobody likes talking about poop, but here’s the quick scoop on what happens in an onsite septic system – the sewage treatment a home needs if not hooked in to a community sewer:

Waste water leaves the house and enters the septic tank. The septic tank acts as a holding tank and allows the solids to settle. The heavier solids sink to the bottom forming the sludge layer; the lighter solids – fats, oils, and grease, rise to the surface and form the scum layer. The relatively clear layer in the middle is called effluent. While this is going on, naturally occurring anaerobic bacteria begin breaking down the solids in size and destroying the pathogens, or germs.

As the effluent enters the drain field, it percolates through the gravel bed where a large portion of the pathogens are destroyed. Pockets of oxygen created by the uneven shape of the gravel allow the more efficient aerobic bacteria to exist. As the effluent exits the drain field, the natural soil completes the treatment process. By the time the effluent has traveled 2-3 feet through the soil all the remaining pathogens have been destroyed.

“What happens in a septic tank is a beautiful thing,” Knopf said. “You have all these little critters working together. When you introduce something that kills what they are doing, it disrupts the process – at least for a while. What’s going on in there is fairly robust and will come back.”

Jim vonMeier, who operates the helpful website septicprotector.com, advises homeowners s to have your septic contractor inspect the system in the beginning to get a benchmark of how the system is operating because they can tell when a system is “cooking” properly.

“The drugs people take can have a negative impact on a septic system,” vonMeier said. “Antibiotics, for example. Antibiotics kill bacteria in your body but that killing process does not stop there. When you go to the bathroom, you are flushing those antibiotics out to your septic system where they kill the ‘good’ bacteria in the tank and soil. Chemotherapy drugs can also have the same effect.”

States and counties have different rules and regulations regarding onsite septic systems. For example, Kitsap County requires that all developed property utilizing an onsite sewage system have the system inspected and evaluated through the Kitsap County Health District prior to conveying the property to a new owner. New homes and businesses that have never been occupied are exempt.

“It’s common to hear that the best solution to pollution is dilution,” Knopf said. “While systems do recover, they are not designed to take everything we give them. For example, in Washington State, kidney dialysis patients are allowed to install a small drain field just for that use. It just depends where you are and what you are dealing with.”

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