Last month I discussed the elements involved in a “proper existing system inspection for real estate transfer.” This was a result of a presentation that I made at the Pumper & Cleaner Environmental Expo International in February. Another question that came up over and over after the seminar was: What should I look for when I inspect the septic tank?

A septic tank holds a wealth of information about the operation and performance of the entire onsite system. Some states only require inspecting the tank because they assume that every question about how the system is operating is determined in the tank. From the information in last month’s Answer Man column, I hope we all agree that is not true.

 

OPENING ACT

To learn all we can from the tank – either as an inspector or as a service provider troubleshooting the system – requires the tank is fully opened. This means at least opening the manhole or manholes. The tank cannot be inspected through the 4-inch observation pipes over the baffles. A number of service providers have told me the only way they can get an adequate view is to remove the entire tank cover. This only happens in areas where systems are installed very shallow.

Assuming the lid is removed, the first task is evaluating the condition of the lid. If it is a concrete lid and there is exposed rebar, the lid is unsafe and likely there are structural problems with the tank. A cracked or damaged lid also means the tank is not watertight. When scum or toilet paper cling to the bottom of the lid, that’s an indication the tank has operated above the normal operating level, a clue there have been system backups.

If there are risers, they should be inspected to see if they are attached properly to the tank to prevent unwanted water or sediment from entering. Connections also are important to keep roots from penetrating.

The operating depth of the tank should be at the invert of the tank outlet. Make sure the tank was installed properly and is level. If the water level is above the invert, there is some type of backup in the system. This could be due to a plugged outlet or a backup from the soil treatment unit.

Take a look at the tank contents. If there is floating material that does not belong there, such as plastic products or undigested food, the owners likely have abused the system and more problems will be discovered with the system.

The tank should develop three distinct layers if it is operating properly. A scum layer will be on top, clear water in the middle and a sludge layer on the bottom. When the layers do not form, it is often because some type of chemical has been added that affects the bacteria, or there are baffles missing. Sometimes it can be due to turbulence in the tank if water is being pumped into the tank.

 

SEE THE SCUM

The scum layer should not be excessively thick; it should always be greater than three inches from the bottom of the outlet baffle to ensure that scum is not leaving the tank. The scum layer should not be higher than the outlet baffle or overflowing the baffle and into the outlet. Excessive scum may simply indicate the tank needs to be pumped. Or it may indicate the wastewater has high levels of soap or grease. Users of the system may be able to reduce the amount of soap or grease, or they just need to have the tank cleaned on a more frequent basis.

Another component of scum can be undigested food. Scum that is thick and contains a large amount of food indicates a problem in the house. It could be excessive use of a garbage disposer or a resident with a medical problem, such as bulimia. The users of the system will have to deal with those issues.

Other problems to check for include feminine hygiene products, baby wipes, other cleaning wipes and condoms. These materials should not be in the septic tank. They will not sink or float, instead they tend to flow through the system. In these cases, having an effluent screen at the outlet baffle helps keep these products from moving downstream, causing plugging problems.

The sludge layer should be measured and it should not be within 12 inches of the bottom of the outlet. Sludge will not settle properly if the water is turbulent. These conditions can result from using too much water or having a pump in the basement adding high volumes of water keeping the tank stirred up. It may simply mean the tank is not large enough to handle the amount of wastewater being put in.

Users may be able to reduce water use and improve tank performance. If excessive material, such as coffee grounds, soil, hair and soap cannot be broken down, the only way to remove them is to pump the tank. Again the users may be able to reduce the amount of these materials put into the tank.

 

A TIGHT TANK

After evaluating the contents the tank should be pumped. Watertightness is the key to proper septic tank operation. Excess water entering the tank from surface runoff can result in overloading the soil treatment area, causing failure. Untreated wastewater entering the soil through cracks in the tank poses a risk to human health and environmental problems. Examine the tank walls to verify they are watertight.

Cracks or leaking around a seam will show up darker than the surrounding area. Check the bottom of the tank. Tank floors can be cracked during installation and sometimes drain holes in the bottom of the tank were not sealed.

All penetrations into the tank should be inspected including inlet, outlet, manhole riser, lid and inspection pipes. All of these should be made watertight. If roots penetrated the tank, it is not watertight.

The inlet and outlet pipes should be evaluated and free from obstruction. The piping in and out should be straight; if not it is subject to plugging and the tank may not vent properly causing excessive corrosion at the outlet baffle. Verify there is enough free space between the inlet pipe and the baffle to allow the free flow of both water and solids. There should be two to four inches between the pipe and the baffle.

People outside the industry or new to the industry don’t always understand how service providers and inspectors can tell so much about how a system is operating simply by looking in the tank. I hope this gives an idea of why a proper inspection of a system requires the tank be opened and pumped.