What’s the Deal with Septic Systems?

Wastewater, or the used or flushed water from our homes, requires treatment to keep us safe from illness and disease and keep our waterways clean. Historically, streams were considered the most efficient way to transport wastewater away from homes and communities. However, that only sent the problem downstream to lakes and other endpoints, including some drinking water sources.

Today, communities typically use two far better approaches to move and process wastewater: municipal sewage systems or on-site sewage disposal systems, commonly known as septic systems. This article will get dirty and dive into septic systems. Look for part 2 on municipal wastewater treatment systems in the Spring 2025 Newsletter.

How it works

Septic systems are designed to treat waste on location. Sewage is carried away from collection points (i.e. toilets and drains) using gravity-fed piping that leads to a septic tank (in most designs). In the tank, the sewage separates into layers, with solids settling to the bottom and fats rising to the surface. The tank is naturally inoculated with bacteria that begin breaking down the solid waste into nutrients and other absorbable components. An outflow pipe is strategically placed to take off the liquid sewage portion. This liquid is then gravity fed out to a network of underground perforated pipes often called a drain field. Bacteria in the soil further break down the nutrients and other elements into fertilizer that plants can use. Excess fluid then travels through the groundwater system. If the septic system does not have a drain field, the tank must be regularly pumped out and the sewage hauled away by a septage hauler.

What is the problem?

Unfortunately, there are a few ways that septic systems can pollute our water. Fifty years ago, it was common practice to connect septic tank outlets directly to waterways (e.g., ditches and streams) or to storm sewers and sometimes directly to groundwater. While this practice is no longer legal, old systems often retain this setup. In other cases, systems have been installed at sites with inadequate or inappropriate soils, excessive slopes, or high groundwater tables. These conditions can also cause failures and contamination of nearby water sources.

Additionally, septic systems do not last forever. Even a well-maintained system may need to be replaced in about 30 years. They can become clogged, leak and eventually fail. If not pumped regularly, the tank can  fill with solids, which slowly migrate and may eventually clog the drain field. Dental floss, wipes (despite misleading packaging, they are NOT safely disposable), and other hygiene products and food waste from garbage disposals can also clog a septic system. Leaking can result from cracks in the tanks or broken drainage pipes due to settling or ground compaction, or from overloading the system with water. This can occur during high precipitation events when a drain field floods, exacerbated by downspouts directed onto the field, or by excessive water discharge from a “running” toilet—as much as 200 gallons per day! Once a septic system becomes clogged or overwhelmed, sewage can pond on the ground near the septic tank or drain field or back up into buildings. This, in turn, can pollute ditches, creeks, and shallow groundwater supplies/wells.

What is the effect on our streams?

Septic contamination in our streams and rivers can lead to growth of bacteria and other pathogens like amoebas and viruses that can make people seriously ill with gastrointestinal disorders. Michigan, as well as most other states, use the concentration of Eschericia coli in the water as an indicator of the level of septic contamination. HRWC samples over 50 sites across the watershed for E. coli levels. Data shows broad bacterial contamination in urban streams. In fact, based on data from the last five years, Huron River tributaries that drain more than 25% residential and commercial land generally exceed state E. coli standards more than half of the time. E. coli values are lower in areas with less residential and commercial development, but data collected from largely agricultural areas like Mill Creek can periodically have very high bacteria concentrations, possibly from manure applications on farm fields.

Are there legal controls?

Michigan is just one of a few states that do not regulate septic fields, though some local agencies do. There are 1.3M septic systems in use across Michigan, with 25% or 330,000 of those estimated to be failing. County governments are mostly responsible for permitting the construction and repair of on-site septic systems. They typically require septic systems to be designed and built according to county standards and inspected and approved by a health inspector. County environmental health inspectors also investigate complaints of failing septic systems. Some counties in Michigan use “Time of Sale” programs to ensure that on-site wastewater systems work properly. Septic systems are inspected at the time of home sale and are required to be brought up to code, or as close as possible to code, depending on the situation. This may include repairs or the installation of a drain field. Out of Michigan’s 83 counties, only 11 have time of sale inspection requirements.

There are three bills pending in the Michigan Legislature that would create a statewide code for septic fields in Michigan. While bills have been introduced by State Rep. Phil Skaggs (House Bill 4479) and State Sen. Sam Singh (Senate bills 299 and 300), hearings have not yet taken place on them in either chamber, a necessary step in the lawmaking process. HRWC, along with other constituent groups across the state, is participating in a legislative workgroup with senator Singh and representative Skaggs to negotiate the issues within the bills. Those issues include the time interval for inspections by local health departments, building a database of septic field permit details from Michigan’s health departments and EGLE, and assisting communities with municipal sewer systems, including expansion of existing systems to transition more properties away from on-site septic systems.

Get more tips on septics

Find resources during SepticSmart Week, September 16-20; learn about municipal systems in the Spring 2025 Huron River Report; and watch our blog for septic bill updates. We all need to do our part to keep the Huron River safe for ourselves and others, so we can continue to enjoy it with peace of mind.

Prevent failures and costly repairs:

• Get septics inspected by a licensed service provider every 1-3 years, and pumped out every 3-5 years or as recommended.
• Learn the signs of a failing septic system and find resources at HRWC.org/septicsystems.
• The Michigan Department of Environment, Great Lakes and Energy (EGLE) recently announced the Michigan Saves program to assist homeowners with low interest loans to replace failing or near-failing septic systems. Learn more at michigansaves.org/septic.

—Ric Lawson , David Lossing, Pam Labadie, and Kelly McCabe

This blog post is also published in the Huron River Report, Fall 2024.