How to inspect a septic tank yourself (and what to leave to a pro)

You can inspect a lot of your septic system without ever opening the tank. Find and mark the tank and lids, walk the drain field, pay attention to how your drains behave, test the alarm if you have one, and keep good records. Opening the tank, measuring sludge and running a camera should be left to a septic professional.

Safety first. Never enter a septic tank, and never lean or put your head into an open one. The tank has very little oxygen and holds hydrogen sulfide, methane and other life-threatening gases. Hydrogen sulfide can also deaden your sense of smell, so you may not notice it. If someone falls in, call 911 and do not go in after them. Keep children and pets away from lids at all times.

What a homeowner can check vs. what needs a pro

Task	Homeowner	Septic professional
Find the tank, lids and drain field	Yes	Can locate buried systems with probes or locators
Walk the yard for wet spots, odors, lush grass	Yes	Yes
Watch drains, toilets and plumbing for warning signs	Yes	Yes
Look at the alarm panel and test the alarm	Yes, using the test button	Repairs floats, pumps and wiring
Keep records of pumping and service	Yes	Provides the written report
Check that lids are intact and fastened	Yes, without removing them	Yes
Open the tank	No	Yes
Measure sludge and scum	No	Yes
Inspect baffles, effluent filter and tank walls	No	Yes
Camera inspection of pipes	No	Yes
Open the distribution box or dig in the drain field	No	Yes

A few places allow homeowners to do their own inspection. Clark County, Washington, for example, lets owners of gravity systems inspect their own tank, but the next inspection must be by a licensed inspector. If you are not in a county with a program like that, and trained for it, leave the inside of the tank alone.

Step 1: Find the tank and lids

You cannot check what you cannot find. EPA suggests these ways to locate the tank:

1. Get the as-built drawing. Your local health department often has the permit and a drawing showing where the tank and drain field are.
2. Look for lids, caps or manhole covers in the yard. Some tanks have a riser, a collar that brings the tank opening up to ground level.
3. Ask the previous owner, your real estate agent, or the company that last pumped it.
4. Hire a septic company to locate it if nothing else works.

On older systems, lids can be buried. Purdue Extension notes that access lids in older neighborhoods can sit 6 to 24 inches below grade. Once you find them, mark the spots on a sketch with measurements from the house. Many owners add risers so future pumping does not require digging.

Check that lids are secure, without opening them. The Washington State Department of Health says to check lids regularly for damage, fasten them with bolts, screws or locks, and replace any cracked or missing parts. Do not drive or park over them, since that can crack or shift a lid. Teach children not to play on or open lids.

Step 2: Walk the yard and drain field

Walk over the tank and drain field every few months and after heavy rain. EPA lists these signs of trouble:

• Standing water or damp, spongy ground over the tank or drain field, especially when it has not rained much
• Grass that is bright green and lush over the drain field, even in dry weather
• Sewage odors around the tank or drain field
• Algae blooms in nearby ponds or ditches

Also look for things that harm the drain field: cars or equipment driving across it, new sheds or patios on it, trees growing nearby, and roof gutters or sump pumps that discharge onto it. The drain field guide explains why each of these matters.

Step 3: Watch your drains and plumbing

The house often warns you before the yard does. EPA’s warning signs include:

• Slow drains in sinks, tubs and showers
• Gurgling sounds in the pipes
• Toilets that flush slowly or back up
• Sewage backing up into the lowest drains

One slow sink is usually a local clog. Several fixtures acting up at once, especially the lowest ones in the house, points to the tank or drain field. If sewage backs up, stop using water and see the septic backup guide.

Step 4: Check the alarm panel

If your system has a pump, it should have a high-water alarm, usually a box with a light and a buzzer mounted on the house or a post. Virginia Cooperative Extension advises buyers to locate and check any high- and low-water alarms on pump or dosed systems.

• Make sure the panel has power and the light is not on.
• Use the test button, if there is one, to confirm the buzzer works.
• Never open the panel’s wiring or the pump tank.

If the alarm sounds, cut back on water use and call a septic company. See what to do when a septic alarm goes off.

Step 5: Keep records

Records are the one part of an inspection only you can do. Keep a folder with:

• The as-built drawing and permits
• Every pumping receipt and inspection report, including sludge and scum measurements
• Repairs and part replacements, such as baffles, filters, pumps or alarms
• Your own notes on yard and drain problems, with dates

EPA recommends recording sludge and scum levels to track when the tank needs pumping, and keeping repair notes in the service report.

A simple homeowner checklist

Use this as a routine. None of it requires opening the tank.

How often	What to check
Monthly	Alarm panel light is off and has power (systems with pumps)
Every few months and after heavy rain	Walk the tank and drain field for wet spots, odors and lush grass
Every few months	Lids and risers are intact and fastened; nothing is parked or stored on them
Ongoing	Slow drains, gurgling, or backups in the lowest fixtures
Ongoing	Downspouts and sump pumps still discharge away from the drain field
After each service	File the receipt and write down the sludge and scum readings
About every 3 years (yearly for systems with pumps)	Book a professional inspection, per EPA

If anything on the list looks wrong, call a septic company rather than investigating inside the tank. For routine care between inspections, see the septic system maintenance guide.

What a professional inspection adds

A septic professional opens every tank and measures what is inside. EPA says to pump when the bottom of the scum layer is within 6 inches of the outlet, the top of the sludge is within 12 inches of the outlet, or sludge and scum fill more than 25% of the liquid depth. The pro also checks baffles, the effluent filter, the tank for cracks and leaks, the distribution box, and the drain field, and may run a camera through the lines.

EPA recommends a professional inspection at least every three years for a typical system and about once a year for systems with pumps or other mechanical parts. NC State Extension also recommends that a professional, not the homeowner, clean the effluent filter, because sewage carries germs and the tank can release toxic gases.

For what to expect and what it costs, read what happens during a septic tank inspection.