How to Inspect a Septic System

Your home’s septic tank system needs to be inspected and pumped periodically in order to keep it functioning smoothly. In this post, we’ll discuss the best DIY method for septic tank inspection.

Your Septic System 101

Before you can inspect your septic system, you need to know a little bit about how your septic system works and what you’re looking for when you inspect the tank.

A septic system consists primarily of a tank buried in the ground, connected to a structure (like your home) via drain pipes. When waste water exits your home out of the toilets and sinks, that water enters the septic tank. Any solids contained in the water (like bits of food from your kitchen sink) will sink to the bottom forming a layer of sludge. Fats and oils float at the top of the septic tank in a layer known as “scum,” and in the middle is a layer of clear(ish) liquid.

Water from septic tank drains into a portion of the yard called the drain field, and when this happens, the water filters through the soil and into the ground water below. The filtering process cleans the water, so that by the time the liquid from the septic tank has entered the ground water, it’s clean enough to drink and water crops.

Over time, the sludge in the bottom of the septic tank grows, as does the scum at the top of the tank. When these layers get too large, the tank must be pumped. This is because sludge or scum that enters the drain field is likely to clog the tank.

The purpose of inspecting your tank, which ideally will be done once per year, is to measure the size of the scum and sludge relative to the size of the tank. When the sludge equals more than 1/3 of the total contents of the tank, or when the scum equals more than 1/3 of the total contents of the tank, that’s when it’s time for your septic tank to be cleaned.

Safety Information

Before inspecting your tank, follow these safety procedures:

Work with a partner.
Never lean over the tank and breathe in the fumes.
Never go in after anyone who has fallen into a tank.
Never go into a septic tank willingly unless you are specially trained for the task.

Remember, septic tanks can contain enough methane gas to cause someone to lose consciousness, and falling into a septic tank is often fatal.

Performing the Inspection

Take a 10 foot 2×4 and mark it with measurement lines every 6 inches, so that when you put it into the tank, you’ll be able to see how far down into the liquid the 2×4 has been inserted.

Slowly insert the 2×4 into the tank. At the top will be a layer of scum. When the 2×4 breaks through the scum to the liquid beneath, you’ll feel the difference. When you feel this happen, note the height of the scum on the board markings.

Next, push the board slowly through the liquid until it reaches the layer of sludge. Again, you’ll be able to feel the difference when this happens. Note the height of the board when it reaches the sludge.

Finally, note the height of the board when it reaches the bottom of the tank. Use the measurements taken on the board to determine the approximate height of the layer of scum and the approximate height of the layer of sludge. For example, if the board was 4 feet into the contents of the tank when it reached the sludge, and 5 feet into the contents of the tank when it reached the bottom, that means there’s 1 foot of sludge at the bottom of a tank that holds 5 feet of waste. If this is the case, then the sludge makes up only 1/5 of the contents of the tank. For a good demonstration of this process, check out this YouTube video:

For more information about inspecting your home’s drainage system, call us at Terry’s Plumbing. We’ll be happy to answer your questions to the best of our ability, and come out if your home’s plumbing system needs help.