Septic Do's and Don'ts: What Not to Flush or Pour

Flush only human waste and toilet paper, keep grease, chemicals and wipes out of every drain, spread out your water use, and keep cars, trees and roof water off the drain field. Those are the core rules from the U.S. EPA and Florida DEP. The EPA puts it simply: "Your septic system is not a trash can." The full do and don't table is below, with the source for each line.

About 30% of Floridians rely on a septic system, according to Florida DEP. DEP's owner's guide says that following its care recommendations can help a system work properly for years to come. A system that gets grease, wipes and too much water at once can clog and fail. DEP's owner's guide notes that repair and replacement can cost thousands of dollars.

Why these rules matter

A septic tank separates and stores solids, grease and oils so the liquid can move on to the drain field. The drain field and the soil under it do most of the treatment, filtering out germs and some nitrogen. Bacteria in the tank break down part of the waste. Each rule below protects one of those steps: keeping the tank from filling with things bacteria can't break down, keeping chemicals from killing those bacteria, and keeping the drain field and its soil working.

How a conventional septic system works

1Wastewater from toilets, showers, sinks and laundry flows out of the house through one main drain pipe to the septic tank.
2In the tank, solids settle to the bottom as sludge, and grease and oils float to the top as scum. Compartments and a T-shaped outlet (often called baffles) keep both inside the tank.
3The liquid in the middle (effluent) flows out of the tank, in many systems through an effluent filter that holds back small solids.
4In many systems, a distribution box splits the effluent evenly between the drain field lines.
5The drain field is a shallow, covered area of unsaturated soil that accepts, treats and disperses the effluent. If it is overloaded or flooded, sewage can surface in the yard or back up into toilets and sinks.

A conventional septic system. Simplified illustration, not to scale; aerobic and mound systems add parts not shown here. Based on U.S. EPA, How Your Septic System Works.

The do and don't table

Each line shows where the advice comes from: EPA's care guide, EPA's SepticSmart flyer, Florida DEP's Septic System Owner's Guide, or a University of Kentucky Extension publication. Links are in the Sources list.

Toilets

	What to do	Source
Do	Flush only human waste and toilet paper.	EPA; Florida DEP
Don't	Flush wipes, even ones sold as "flushable," or kitty litter.	Florida DEP
Don't	Flush feminine hygiene products, condoms, dental floss, diapers, cigarette butts, paper towels or medicines.	EPA; EPA SepticSmart
Do	Put those items in the trash instead.	EPA SepticSmart
Do	Keep "every flush" or automatic toilet bowl cleaners to a minimum.	Univ. of Kentucky Extension

Sinks and drains

	What to do	Source
Don't	Pour cooking oil or grease down a sink or toilet.	EPA; EPA SepticSmart; Florida DEP
Do	Let grease harden in a container, then put it in the trash.	EPA SepticSmart
Don't	Rinse coffee grounds into the sink.	EPA SepticSmart
Don't	Use chemical drain openers. For a clogged sink drain, try boiling water or a drain snake.	EPA
Don't	Pour oil-based paints, solvents or large amounts of toxic cleaners down the drain.	EPA
Don't	Pour strong chemicals, cleansers or unwanted medicines down drains or toilets.	Florida DEP
Do	Eliminate or limit use of a garbage disposal.	EPA; EPA SepticSmart; Florida DEP
Do	Use a sink strainer to catch hair, grease and food.	Univ. of Kentucky Extension

Water use

	What to do	Source
Do	Fix leaking faucets and running toilets promptly.	EPA; Florida DEP
Do	Spread laundry over the week instead of doing it all in one day.	EPA; Florida DEP
Do	Run only full loads if your washer cannot set the load size.	EPA
Don't	Run the dishwasher, shower, washing machine and toilet all at once.	EPA SepticSmart
Do	Consider faucet aerators, high-efficiency showerheads and toilets.	EPA; EPA SepticSmart
Don't	Let water softener backwash into the system. Reroute it at least 15 feet from the tank and drain field.	Florida DEP
Don't	Drain chlorinated pool or hot tub water into the septic system.	Univ. of Kentucky Extension

The drain field

	What to do	Source
Don't	Drive or park on the drain field or over the tank.	EPA; EPA SepticSmart; Florida DEP
Do	Plant grass over the drain field.	Florida DEP; EPA
Don't	Plant trees, shrubs or a vegetable garden on the drain field.	EPA
Do	Ask a septic professional how far away to plant trees and shrubs.	EPA SepticSmart
Do	Point downspouts, roof drains and sump pumps away from the tank and drain field.	EPA; Florida DEP
Don't	Pave over the drain field with concrete or asphalt.	EPA
Don't	Cover any part of the drain field without a permit, or dig around it.	Florida DEP

Upkeep

	What to do	Source
Do	Have the system inspected at least every 3 years and the tank pumped every 3 to 5 years, or as your septic company advises.	EPA; EPA SepticSmart
Do	Keep your permit paperwork and service records.	EPA; Florida DEP
Do	Mark the tank location and take a photo when it is pumped.	Florida DEP
Do	Call 811 (Sunshine State One Call of Florida) before you probe or dig to look for the tank, so buried utilities can be located first.	Florida DEP
Do	Learn Florida's maintenance rules if you have an aerobic treatment unit.	Florida DEP

What not to flush

The toilet rule is the one most people break without knowing it. EPA's list of things never to flush includes cooking grease or oil, non-flushable wipes, photographic solutions, feminine hygiene products, condoms, dental floss, diapers, cigarette butts, coffee grounds, cat litter, paper towels, pharmaceuticals and household chemicals. Florida DEP goes a step further on wipes: its owner's guide says anything other than human waste and toilet paper, including "flushable" wipes and kitty litter, can clog or damage the system.

Medicines are on both lists for a second reason. DEP says strong chemicals, cleansers and unwanted medicines can kill the bacteria in the tank that help treat sewage.

What not to pour down the sink

Grease and cooking oil. DEP says grease can clog the drain field. EPA's SepticSmart flyer suggests letting it harden in a container and throwing it in the trash.
Chemical drain openers. EPA says to avoid them and use boiling water or a drain snake for a clogged drain. The University of Kentucky notes that frequent use of strong acid or lye products can harm the bacteria and even damage plumbing, tanks and other parts.
Paints, solvents and large amounts of toxic cleaners. EPA says never to pour these down a drain. The Kentucky guide suggests local recycling and hazardous waste collection programs instead.
Food waste. EPA says to eliminate or limit the use of a garbage disposal, which cuts the fats, grease and solids reaching the tank. DEP adds that if you use a disposal, you should have the tank checked more often than usual. See how often to pump a septic tank for how a disposal changes the schedule.

EPA's warning is about large volumes of toxic cleaners, and the Kentucky guide says occasional, small use of strong drain products will probably have little effect. It suggests simple options such as baking soda and vinegar in place of harsh chemical cleansers.

Use water wisely

Every gallon that goes down a drain passes through the tank and into the drain field. EPA says excess water slows down or stops the treatment process. It gives some numbers worth knowing:

A typical single-family home can use as much as 70 gallons of water per person per day indoors.
A single leaky or running toilet can add as much as 200 gallons a day.
Toilets account for 25 to 30% of household water use. Newer high-efficiency toilets use 1.6 gallons or less per flush.

Laundry is the easy win. EPA says doing all the household laundry in one day might seem like a time-saver, but it can harm a septic system. Spread loads through the week, and run only full loads if your machine can't set the load size. EPA's SepticSmart flyer adds: don't run the dishwasher, shower, washing machine and toilet at the same time, especially if the tank hasn't been pumped in a long time.

Two Florida-specific points from DEP's guide: route water softener backwash at least 15 feet away from the tank and drain field, and divert downspouts away from the system. Too much water in the drain field area prevents proper treatment. If your drain field already struggles after heavy rain, read why Florida drain fields struggle in the rainy season.

Protect the drain field

The drain field does most of the treatment, and it is easy to damage from above.

No cars or trucks. EPA says not to park or drive on it, because the weight compacts the soil and can damage the pipes. DEP says to keep vehicles off the tank too.
Grass only. DEP says to plant only grass over or near the drain field, because tree and shrub roots can grow in from long distances and clog it. EPA suggests native grasses and ground covers, and advises against trees, shrubs and vegetable gardens on top.
No paving. EPA says concrete and asphalt should not go over a drain field, because they reduce evaporation and the supply of oxygen to the soil.
No digging or covering. DEP says not to cover any part of the drain field without a permit, and not to dig around it.
Keep rainwater away. Point roof drains, sump pumps and other rainwater drainage away from the area (EPA).

Planning a pool, shed, patio or new driveway? Find the tank and drain field first. DEP's guide suggests checking your permit paperwork for a site plan, and calling 811 before you dig to locate buried utilities. If a drain field is already failing, see drain field repair.

Keep up with maintenance

Good habits slow how fast the tank fills, but they don't replace pumping. EPA says household tanks are typically pumped every 3 to 5 years and inspected at least every 3 years. Keep your receipts. DEP's guide includes a page for your permit details and a maintenance log, and notes that good records can be a selling point when you sell the home.

If you have an aerobic treatment unit, Florida law requires a service contract with a maintenance entity that inspects it at least twice a year. See aerobic system service.

You don't need to buy anything to keep the bacteria going. EPA does not recommend septic additives, because the system already contains the bacteria it needs. Our guide to septic tank additives explains why.

Frequently asked questions

Can I use bleach with a septic system?

The sources we reviewed warn against large volumes of toxic cleaners and against strong chemicals that kill the tank's bacteria. They do not ban normal household cleaning. The University of Kentucky guide says occasional, small use of strong drain products will probably have little effect. Use cleaners as the label directs, avoid pouring large amounts down the drain, and keep automatic toilet bowl cleaners to a minimum.

Are "septic-safe" or "flushable" wipes OK?

Florida DEP says not to flush anything but human waste and toilet paper, and names "flushable" wipes as something that can clog or damage the system. Put wipes in the trash.

Can I have a garbage disposal with a septic tank?

You can, but EPA says to eliminate or limit its use, and DEP says to have the tank checked more often if you use one.

Is it OK to plant over my drain field?

Grass, yes. DEP says to plant only grass over or near it. Ask a septic professional how far from the system to plant trees and shrubs.

What should I do if I flushed something I shouldn't have?

Watch how your drains behave over the next few days. If they slow down, gurgle or back up, read the signs a septic tank is full and call a septic company. You can find one in the directory.