How often should a septic system be inspected?

Short answer

Inspect the septic system every 1 to 3 years. A system with pumps, float switches or other mechanical parts needs a look every year, because those parts fail. The inspection is a professional job: the inspector opens the tank, measures the layers of scum and sludge, checks the baffles and the outlet, and walks the drain field. It takes 60 to 120 minutes and costs $150 to $450.

Why it matters

A septic tank is a settling chamber. Solids sink to the bottom as sludge, fats float to the top as scum, and the water in between flows out to the drain field, where the soil finishes cleaning it. The tank has to be pumped before the sludge and scum build up enough to escape with the water, and the only way to know when is to measure them. That measurement is the heart of an inspection.

The drain field is the expensive part. Once solids reach it, the soil clogs, the water has nowhere to go, and the yard goes soggy. A failed drain field means digging up a new one, which costs far more than years of inspections and pumping combined. An inspector also catches a cracked baffle, a sagging outlet pipe or a failing pump while they're cheap repairs, and keeps a record that matters if you ever sell the house.

When to do it more often

• Pumps, float switches, alarms or an aerobic treatment unit: every year. Mechanical parts in a septic system live in a harsh place and need checking.
• A larger household than the system was designed for, or a garbage disposal feeding the tank: lean toward the yearly end of the range, since the tank fills faster.
• Any of the signs below: call for an inspection then rather than waiting for the schedule.

What you need

Nothing. The inspector brings the tools. What helps is knowing where the tank lids are, or having the system's drawing from when the house was built, and having the records of the last pumping so the inspector can judge how fast the tank fills.

Steps at a glance

1. Find the tank lids and clear anything on top of them before the visit.
2. The inspector opens the tank and measures the depth of the scum layer on top and the sludge on the bottom.
3. They check the inlet and outlet baffles, which keep solids from leaving the tank.
4. They look at the effluent filter, if the tank has one, and clean it.
5. They test any pump, float or alarm, and walk the drain field looking for wet spots and lush growth.
6. They tell you whether the tank needs pumping now, and when to expect it next.

You're done when you have the inspector's measurements and a date for the next pumping.

Signs it's overdue

• Slow drains through the whole house, not just one fixture.
• Gurgling in the pipes when a sink or tub drains.
• A sewage smell near the tank or the drain field.
• A soggy drain field, or grass over it that's greener than the rest of the yard.
• Backups into the lowest drains in the house.

DIY or pro

This is a pro-recommended job. Opening a septic tank is dangerous work: the gases inside can overcome a person in seconds, and the lids are heavy. Measuring sludge properly takes a tool and some experience. The parts you can do yourself are watching for the signs above, keeping the drain field clear of vehicles and trees, and keeping grease and wipes out of the drains.

The inspection costs $150 to $450, and many companies combine it with pumping when the tank needs it, which saves a second visit. If the system has an alarm panel, learn what its lights mean, because the alarm is the system asking for the inspector early.

Safety

• Chemicals: the gases in a septic tank, hydrogen sulfide and methane, can overcome a person within seconds of leaning over an open lid. Don't open the tank yourself, don't go near an open one, and keep children and pets away while the inspector has the lids off. If a lid is cracked or sitting loose in the yard, cover it and call for a replacement before anyone steps on it.

FAQ

How do I know if my septic tank needs to be inspected?

Go by the schedule, every 1 to 3 years, unless the drains slow, the pipes gurgle, or the yard over the drain field is wet or unusually green. Any of those means call now.

Can I inspect my own septic tank?

Opening the tank is risky because of the gases inside, and measuring the sludge takes a tool. Leave the tank to a professional and do the watching from the yard.

What does a septic inspection include?

Measuring the scum and sludge layers, checking the baffles and outlet, cleaning the effluent filter, testing any pumps and alarms, and looking over the drain field.

Is a septic inspection the same as pumping?

No. The inspection measures the tank and tells you whether pumping is due. Pumping empties it. They're often done on the same visit when the tank is full.