How Often Should You Pump a Septic Tank? In Plain Words

EPA’s pumping answer, in EPA’s own words

On its page “How to Care for Your Septic System,” the EPA says:

“The average household septic system should be inspected at least every three years by a septic service professional. Household septic tanks are typically pumped every three to five years. Alternative systems with electrical float switches, pumps, or mechanical components should be inspected more often, generally once a year. A service contract is important since alternative systems have mechanized parts.”

On its “Frequent Questions on Septic Systems” page, the EPA answers the question “How often should my septic tank be pumped?” this way:

“In general, a septic tank should be inspected every 1 to 3 years and pumped every 3 to 5 years.”

In plain words: both EPA pages give the same pumping range — typically every three to five years. The inspection timing is worded two different ways on EPA’s own pages — “at least every three years” on the care page, and “every 1 to 3 years” on the questions page — so both wordings are printed here, not merged into one number.

What changes how often

The EPA care page lists these as the major factors that influence how often to pump your septic system:

• Household size
• Total wastewater generated
• Volume of solids in wastewater
• Septic tank size

The EPA questions page says it this way: “The frequency of pumping the septic tank depends on the tank size, number of people in the household, habits of water use as well as the amount of solids accumulated in the tank. Some alternative systems that are more complex may require more frequent inspection or pumping. If you are unsure, ask your local septic system professional.”

A garbage disposal changes the timing too. The EPA says using an in-sink garbage disposal unit can impact how often you need to pump your septic tank, because food waste can accumulate as scum and sludge — and if you must use a garbage disposal unit, your tank will need to be pumped more frequently.

The sludge and scum measurements EPA prints

EPA’s care page says that when you call a septic service provider, he or she will inspect for leaks and examine the scum and sludge layers in your septic tank. The same page then gives these measured conditions for pumping, in EPA’s words:

“Your tank should be pumped if the bottom of the scum layer is within six inches of the bottom of the outlet, if the top of the sludge layer is within 12 inches of the outlet, or if more than 25 percent of the liquid depth is sludge and scum.”

EPA’s questions page states a different trigger, as a rule of thumb: “A rule of thumb is to pump the tank when the solids are two-thirds of the volume in the tank.”

Those two statements are not the same number, and this page does not merge them. The care page gives the 25 percent measurement; the questions page gives the two-thirds rule of thumb. Either way, the layers are measured by the septic professional at service time. EPA’s care page adds: “To keep track of when to pump out your tank, write down the sludge and scum levels found by the septic professional.”

How a septic system works, in EPA’s words

EPA’s “Septic Systems and Surface Water” page says household wastewater is treated by a septic system before it filters into the soil. It describes the two main parts this way:

• The septic tank. “Wastewater generated in your home exits through a drainage pipe and into a septic tank. The septic tank is a buried, water-tight container that holds wastewater for separation and treatment. The solids settle to the bottom (sludge) and fats, oil and grease float to the top (scum). Microorganisms act to break down the sludge and destroy some of the contaminants in the wastewater.”
• The drainfield. “The drainfield is a shallow, covered trench made in the soil in your yard. Partially treated wastewater from the septic tank flows out through the drainfield, filters down through the soil and enters the groundwater. If the drainfield is overloaded with too much liquid or clogged with solids, it will flood and cause sewage to surface in your yard or back up into your home.”

EPA’s care page describes the drainfield the same way, in shorter words: it is a component of your septic system that removes contaminants from the liquid that emerges from your septic tank. The care page also says your septic tank includes a T-shaped outlet which prevents sludge and scum from leaving the tank and traveling into the drainfield area.

And one point the care page makes plainly: everything that goes down your drain ends up in your septic system — whether you flush it down the toilet, grind it in the garbage disposal, or pour it down the sink, shower, or bath.

Use water efficiently

EPA’s care page says septic system maintenance comes down to four key elements: inspect and pump frequently, use water efficiently, properly dispose of waste, and maintain your drainfield. For water, the page says:

• The average indoor water use in a typical single-family home can be as much as 70 gallons per individual, per day. Just a single leaky or running toilet can add as much as 200 gallons of water per day.
• All the water a household sends down its pipes ends up in its septic system. The more water a household conserves, the less water enters the septic system. Efficient water use improves the operation of a septic system and reduces the risk of malfunctions.
• Toilet use accounts for 25 to 30 percent of household water use. Replacing existing toilets with high-efficiency models is an easy way to reduce the amount of household water entering your septic system.
• Faucet aerators, high-efficiency showerheads, and shower flow restrictors help reduce water use and the volume of water entering your septic system.
• For washing machines: select the proper load size, or run only full loads of laundry. Try to spread washing machine use throughout the week — doing all household laundry in one day can harm your septic system, because it will not allow your septic tank enough time to treat waste and could flood your drainfield.

What not to flush, and what not to pour down the drain

EPA’s care page gives this rule of thumb: do not flush anything besides human waste and toilet paper. The questions page says the same thing in one line: “Only flush human waste and toilet paper down the toilet.”

The care page lists these items under “Never flush”:

• Cooking grease or oil
• Non-flushable wipes, such as baby wipes or other wet wipes
• Photographic solutions
• Feminine hygiene products
• Condoms
• Dental floss
• Diapers
• Cigarette butts
• Coffee grounds
• Cat litter
• Paper towels
• Pharmaceuticals
• Household chemicals like gasoline, oil, pesticides, antifreeze, and paint or paint thinners

At the sink, EPA’s care page says your septic system contains a collection of living organisms that digest and treat household waste, and pouring toxins down your drain can kill these organisms and harm your septic system. The page lists:

• Avoid chemical drain openers for a clogged drain. Instead, use boiling water or a drain snake.
• Never pour cooking oil or grease down the drain.
• Never pour oil-based paints, solvents, or large volumes of toxic cleaners down the drain. Even latex paint waste should be minimized.
• Eliminate or limit the use of a garbage disposal. This will significantly reduce the amount of fats, grease, and solids that enter your septic tank and could clog the drainfield.

The questions page adds, in its own words, not to pour grease (such as fats, butter, wax, cheese, heavy cream), liquid wastes (such as pesticides, drain cleaners, household chemicals, paints, paint thinners), oils or coffee grounds down the drain — because many materials poured down the drain do not easily decompose and can be harmful to the healthy bacteria that grow in your septic tank and drainfield to help break down organic matter.

Protect the drainfield

EPA’s care page lists three things to do to maintain your drainfield:

• Parking: Do not park or drive on your drainfield.
• Planting: Plant trees the appropriate distance from your drainfield to keep roots from growing into your septic system. A septic service professional can advise you of the proper distance, depending on your septic tank and landscape.
• Placing: Keep roof drains, sump pumps, and other rainwater drainage systems away from your drainfield area. Excess water slows down or stops the wastewater treatment process.

The questions page adds that most drainfields are not designed to handle vehicles or heavy equipment driving on them — the weight compacts the soil, which can damage pipes — and that you should not build any structures in or on your drainfield area without checking with a local designer or permitting authority.

Additives: EPA’s position, in EPA’s words

EPA’s questions page asks, “Are additives recommended for septic systems?” and answers: “No.” The page says, in its words:

“Septic tank additives containing bacteria or chemicals are commonly marketed to improve system performance. However, use of these additives is not recommended for domestic wastewater treatment because there is already a significant presence of bacteria, enzymes, yeasts, fungi, and other microorganisms in onsite wastewater treatment systems. Additive products can be ineffective or even harm system operation and the environment. Any operational issues should be assessed by a septic system professional or local regulator.”

The same page also says: “EPA does not make recommendations on individual septic system products.” It says additives are not necessary for a septic system to function properly when treating domestic wastewater, and: “In general, do not use additives made of organic solvents or strong alkali chemicals because they pose a potential threat to soil structure and groundwater.”

Who does the work, and where the records are

EPA’s pages route this work to professionals and local records, not to do-it-yourself steps:

• Inspection and pumping are done by a septic service professional. EPA’s care page says to keep the maintenance records on work performed on your septic system, and that the service provider should note repairs completed and the tank condition in your system’s service report. If other repairs are recommended, hire a repair person soon.
• The questions page says the owner of the system is responsible for the overall operation, maintenance, and upkeep of the system, including repairs or replacement, and that system users are responsible for proper use of the system, such as what materials go down the drain and how much water is used.
• For your system’s paperwork, the questions page says a septic system is typically permitted and inspected by your local permitting authority (i.e., local health or environmental department), and you can contact these entities to obtain a copy of your property’s septic record drawing (the “as-built” design) and copies of the permit(s).
• For finding help, the questions page says to contact your local permitting authority for a list of professional inspectors in your area, and that many states will license or certify septic system installers, with your local health department able to provide additional information on licensed professionals.