How often should a septic tank be pumped?

The U.S. Environmental Protection Agency recommends having a household septic system inspected at least every three years by a septic professional, and the tank pumped typically every three to five years. Systems with electrical float switches, pumps or mechanical components, such as aerobic treatment units, should be checked more often, generally once a year.

Three to five years is a starting point, not a fixed schedule. The right interval for your home depends on how fast solids build up in the tank.

What makes a tank fill faster

• Household size: more people means more wastewater and more solids for the same tank.
• Tank size: a small tank serving a large family fills quickly. The size is usually on the permit or the last pumping record.
• Total wastewater: long showers, back-to-back laundry loads and leaking fixtures push water through the tank faster, which leaves less time for solids to settle.
• Volume of solids: a garbage disposal adds a large amount of food solids. Grease, wipes and paper towels do not break down.

How the pumper decides it is time

During an inspection, the professional measures two layers inside the tank:

• the scum layer on top (grease and floating material);
• the sludge layer at the bottom (heavier solids).

EPA guidance is to pump when the bottom of the scum layer is within six inches of the outlet, or the top of the sludge layer is within twelve inches of the outlet. If solids escape through the outlet, they clog the drain field, which is the most expensive part of the system to replace.

Keep a record

Write down each pumping and inspection: date, company, measured layers, and anything the technician noticed (damaged baffle, missing effluent filter, standing water). Your records make the next visit faster, help you see how quickly your tank fills, and are useful when you sell the house. Some counties also require pumping or inspection reports.

Not sure when it was last pumped?

If you just bought the house or cannot find a record, schedule an inspection and pumping now: it resets the clock and tells you the real condition of the tank. Describe your system in the form and licensed local pumpers get back to you.