What Should You Never Flush or Pour Down the Drain on a Septic System in Colorado Springs?

What to keep out of your toilets and drains, how garbage disposals, drain cleaners, laundry habits and additives affect a septic system, and what to do if the wrong thing went down.

What should you never flush down the toilet on a septic system?

Anything other than human waste and toilet paper. That is the rule of thumb from the U.S. EPA.

The EPA (retrieved 2026-10-31) says never to flush these items, because they could clog your system and cause a failure:

• cooking grease or oil;
• non-flushable wipes, such as baby wipes and other wet wipes;
• photographic solutions;
• feminine hygiene products;
• condoms;
• dental floss;
• diapers;
• cigarette butts;
• coffee grounds;
• cat litter;
• paper towels;
• pharmaceuticals;
• household chemicals such as gasoline, oil, pesticides, antifreeze, and paint or paint thinners.

The EPA's homebuyer's guide sorts common household items into "cloggers" and "killers". Cloggers such as diapers, baby wipes, cat litter and grease block the system. Killers such as household chemicals, gasoline, pesticides, antifreeze and paint kill the microbes that treat the wastewater, and the guide also lists "high amounts of anti-bacterial soaps and detergents" as killers.

Can you pour grease down the drain or use a garbage disposal on a septic system?

Don't pour grease down the drain, and limit the disposal. The EPA says never to pour cooking oil or grease down the drain, and to eliminate or limit your use of a garbage disposal.

Grease covers more than the frying pan. The EPA names fats, butter, wax, cheese and heavy cream, and says to keep oils and coffee grounds out of the drain too. Many of these materials don't decompose easily, and they can harm the bacteria that break down organic matter in the tank and drainfield. The EPA's additives fact sheet says to dispose of waste in the trash instead of down the drains.

A disposal adds solids. The EPA says food waste is digested slowly and can build up as scum and sludge, and that solids pushed into the drainfield can clog its pipes. If you do use a disposal, it says "your tank will need to be pumped more frequently". See how often to pump a septic tank for the typical intervals.

Can you use chemical drain cleaners on a septic system?

Avoid them. For a clogged drain, the EPA says to use boiling water or a drain snake instead of a chemical drain opener.

A septic system relies on living organisms to digest and treat household waste, and the EPA warns that pouring toxins down the drain can kill them. It also says never to pour oil-based paints, solvents or large volumes of toxic cleaners down the drain, and to minimize even latex paint waste.

The risk doesn't stop at the tank. The EPA says harmful chemicals put down the drain can be discharged into groundwater and affect drinking water supplies. That matters on lots with a private well as well as a septic system, which our Black Forest page covers.

If the same drains keep running slowly, the clog may not be the real problem. See signs your septic system needs service.

Should you spread out laundry on a septic system?

Yes. The EPA says to spread washing machine use through the week, because doing all the laundry in one day doesn't give the tank enough time to treat waste and could flood the drainfield.

All the water a household sends down its pipes ends up in the septic system. Indoor use in a typical single-family home can be as much as 70 gallons per person per day, the EPA says, and a single leaky or running toilet can add as much as 200 gallons a day.

El Paso County sizes new single-family systems for at least 75 gallons per person per day, so a three-bedroom home has a design flow of 450 gallons a day (Chapter 8, section 8.6.A.2.a and Table 6-1). That figure is a design assumption, not a daily allowance.

The EPA's other water tips are to match the washer's load setting to the load (or run only full loads) and to fit high-efficiency toilets, faucet aerators and showerheads. Its homebuyer's guide adds that you should repair any leaks. The EPA also says to keep roof drains, sump pumps and other rainwater drainage away from the drainfield, because excess water slows or stops treatment.

Do septic tank additives help?

No. The EPA does not recommend additives containing bacteria or chemicals, because a septic system already contains the microorganisms it needs and some products can harm it.

The EPA's additives fact sheet (updated 2024; retrieved 2026-10-31) describes these common types:

• Line and drainfield cleaners usually contain strong acids or alkalis, similar to popular drain cleaners. They can affect how bacteria break down waste, and can damage pipes, tanks and other components.
• Degreasers often contain organic solvents, which can destroy helpful microorganisms and pose significant risks to groundwater. Products containing organic solvents are banned for septic use in many states.
• Odor control products work by killing bacteria that the treatment process depends on. The fact sheet says a septic professional should investigate the source of an odor.
• Biological additives can reduce scum and sludge in some cases, but the impact of long-term use on the soil's ability to treat wastewater is unknown.

Additives don't take the place of pumping. The EPA adds that some states and localities have their own rules on additives, so check with your local health department before using one.

What should you do if something went down the drain that shouldn't have?

Don't try to fix it with a drain opener or an additive. The EPA says operational issues should be assessed by a septic system professional or local regulator.

None of the sources on this page gives a procedure for one accidental flush, so what follows applies their general guidance. The EPA (retrieved 2026-10-31) says to contact a local septic system service provider or your local health department for help.

• Write down what went in, how much and when. A provider or the county can't advise you without it. If it was gasoline, solvent or a large amount of another chemical, say so, given the EPA's groundwater warning above.
• Watch for warning signs. The EPA lists backups, very slow drains, gurgling in the plumbing, damp spots over the tank or drainfield, and sewage odors. See signs your septic system needs service.
• Find a licensed cleaner if the problem may be in the tank. El Paso County Public Health publishes a Licensed Cleaners list. This site doesn't rank or endorse any of them.
• Stop using the system if it backs up. El Paso County Public Health's septic guidance (written for homes after a wildfire) says that if a system is damaged, backing up or malfunctioning, "discontinue use" and contact its Environmental Health Division. See what to do in a septic backup.
• If anyone is in danger, treat it as an emergency. El Paso County Public Health's contact details say "In case of emergency, call 911".

Who is responsible for what goes into a septic system in El Paso County?

The owner carries the ultimate responsibility for the system, and a renter is responsible for using it properly. El Paso County Public Health estimates that about 30,000 systems are operating in the county.

Chapter 8 (section 8.14.A) makes the owner responsible for maintaining the system in compliance with state law and county rules. Owners can assign maintenance by contract to a tenant or a third party, but that "does not relieve owners of the ultimate responsibility for their systems".

The EPA says that if you rent a home, "you have responsibility for the proper use and operation of the system". Sharing this page's list with tenants and guests is a simple way to cover that.