Septic System Care: What the US EPA Advises Homeowners and Buyers

A septic system is a small sewage treatment plant in your own garden. The US Environmental Protection Agency (EPA) gives simple care rules. Local rules vary, so also check with your local health department.

This guide is based on the public sources listed at the end. We have not tested the products or services mentioned.

Do you have one, and where is it?

The EPA's homebuyer guide says you most likely have a septic system if you are on well water, the water line coming into the house has no meter, your neighbours have septic systems, or you live in a rural area. To find it:

• Ask your local health department for the "as built" drawing.
• Look in the yard for inspection caps, lids or manhole covers.
• Ask a septic service provider, the seller or the realtor.

How it works

1. All water runs out of the house through one main drainage pipe into the septic tank, a buried, water-tight container.
2. The tank holds wastewater long enough for solids to settle to the bottom (sludge) while fats, oil and grease float to the top (scum).
3. In a conventional system, the liquid leaves the tank and is spread evenly through the drainfield, usually through a distribution box. Systems with more advanced treatment may have an extra component in between.
4. In the drainfield the wastewater percolates into the soil, which removes harmful bacteria, viruses and some nutrients.

The details vary with soil type and site conditions.

Inspection and pumping

The EPA gives two figures: its care page says to have a professional inspect the system at least every three years, while its homebuyer guide says a typical system should be inspected every three to five years. A tank is generally pumped about every three to five years, as the provider recommends or local rules require. Systems with pumps, float switches or other mechanical parts need a yearly inspection.

Pump the tank if any one of these is true:

• The bottom of the scum layer is within 6 inches of the tank outlet.
• The top of the sludge layer is within 12 inches of the outlet.
• Sludge and scum are more than 25% of the liquid depth.

The homebuyer guide says the average lifespan of a septic system is 15 to 40 years, longer with good maintenance. It puts routine maintenance at typically $250 to $500 (nationwide industry estimates), against thousands to tens of thousands of dollars to repair or replace a system. Ask local providers for an estimate.

What not to flush or pour away

Only human waste and toilet paper should go down the toilet. The EPA calls these "cloggers": wipes (even "flushable" ones), diapers, cat litter, cigarettes, coffee grounds, grease, paper towels and feminine hygiene products. It calls these "killers": household chemicals, gasoline, oil, pesticides, antifreeze, paint and high amounts of antibacterial soaps and detergents.

Water use

Indoor use can reach about 70 gallons per person per day, and one running toilet can add roughly 200 gallons a day. Spread laundry across the week, use high-efficiency fixtures (1.6 gallons or less per flush) and repair leaks.

Protect the drainfield

• Keep cars and anything heavier than a lawnmower off it, and do not build on it without local approval.
• Avoid concrete or asphalt over it, and plant trees away from it, because roots can clog the field. Skip vegetable gardens.
• Keep roof drains, sump pumps and excess irrigation away from it.
• Limit or avoid a garbage disposal, which adds fats, grease and solids.

Warning signs

Call a septic service provider promptly if you notice wastewater backing up or gurgling in drains, a strong odour near the tank or drainfield, or bright green, spongy grass on the drainfield.

Buying a home with a septic system

The EPA says to have the system inspected by a septic service provider before you buy. Inspections may also be required by local or state government or by a mortgage lender. A checklist from the homebuyer guide of what an inspector looks at:

See also our guide to upflush toilets for basements.

Last checked: 15 October 2026. Sources: US EPA, how to care for your septic system; US EPA, new homebuyer's guide to septic systems (EPA-832-F-17-009, August 2017).