Septic systems, pumping and what never goes down the drain

A septic system treats the house's wastewater in a buried tank and a drainfield. Have it inspected and pumped on schedule, and keep harmful things out of the drains.

Inspection and pumping

Have a septic professional inspect a typical household system at least every three years. Most household tanks need pumping every three to five years. A system with an electric float switch, pumps or other mechanical parts needs inspecting more often, usually once a year.

How often a tank needs pumping depends on:

• The number of people in the house
• The amount of wastewater they send down the drains
• The amount of solid waste in it
• The size of the tank

On a service visit, the technician checks for leaks and measures the scum layer floating on top and the sludge layer on the bottom. The service report should list any repairs done and the tank's condition. If it recommends a repair, have it done soon.

When the tank is due

The tank has a T-shaped outlet that keeps scum and sludge from flowing out into the drainfield. Pump the tank when any of these is true:

• The bottom of the scum layer is within 6 inches of the bottom of the outlet.
• The top of the sludge layer is within 12 inches of the outlet.
• Scum and sludge together take up more than 25 percent of the tank's liquid depth.

Write down the levels from each visit with the date. They tell you when to book the next pumping. Keep the reports together with the rest of the system's records.

What goes down the drain

Everything you flush, grind in the disposal or pour down a sink or tub ends up in the tank. Flush only human waste and toilet paper. Keep these out of the toilet:

• Cooking grease or oil
• Wet wipes and baby wipes
• Feminine hygiene products, condoms and diapers
• Dental floss and cigarette butts
• Coffee grounds, cat litter and paper towels
• Medicines
• Gasoline, oil, pesticides, antifreeze, paint and paint thinner

The tank works because bacteria in it break down the waste, and harsh chemicals kill them. Don't use chemical drain openers. Use boiling water or a drain snake instead. Don't pour oil-based paint, solvents or large amounts of strong cleaners down the drain. Use the garbage disposal as little as you can, since food waste adds solids that fill the tank faster.

Water use

The less water goes into the tank, the better it works. A single running toilet can waste up to 200 gallons a day, so fix one as soon as you notice it. Spread laundry across the week instead of doing it all in one day. A day of back-to-back loads doesn't give the tank time to treat the waste and can flood the drainfield. Swapping in a WaterSense showerhead and faucet aerator covers two easy ways to use less.

The drainfield

The drainfield is the area of buried pipes where liquid from the tank soaks into the soil and gets filtered.

• Don't drive or park on it.
• Keep tree roots away. Plant trees far enough from it that the roots can't reach the pipes. A septic professional can tell you how far for your yard.
• Keep rainwater off it. Point roof drains, sump pump lines and other drainage away from it. Extra water slows or stops the treatment.

An annotated example

What to do next

Find the date of the last inspection and pumping in your records or the seller's papers. If it was more than three years ago, book an inspection.