1. All POWTS (i.e. Septic systems and Mound systems) eventually fail to accumulation of waterborne solids which plug up the soil pores forming a ‘bio’ (clogging) mat. Once the bio-mat becomes impermeable to water, water follows the path of least resistance, eventually working its way to the ground surface causing system failure. System failure discussed here is sewage discharge on the surface of the ground and/or backing up of the sewage into the home or other building being served by the POWTS.

2. All ‘typical’ POWTS served by merely a septic tank are considered anaerobic, having little to no oxygen. The bacteria that live in an anaerobic environment do very little breakdown of the solids. The septic tank although providing initial treatment is primarily a settling tank. Larger solids will settle to the bottom of the tank while lighter solids such as grease and hair will float to the top of the tank.

3. Solids accumulate in a septic tank. Septic tanks operate on detention time of the liquids flowing through the tank. The longer liquid is in the tank (the longer the detention time), the more solids will settle out of the water. One of the variables of how long the detention time will be is volume of the tank. However, as solids accumulate in the tank, volume available in the tank is reduced. The decrease in volume available, caused by accumulation of solids causes the water to go through the tank faster, carrying with it a higher percentage of waterborne solids. These waterborne solids flowing out of the tank are what will eventually cause failure of the system.

4. Solids only have two (normal) ways out of a tank: 1). Flowing out of the tank with the water and plugging up the soil pores causing eventual failure. 2). Pump them out of the tank by a septage operator (pumper) and safely hauled away.

5. There will be those naysayers who say pumping annually is too frequent, that you are removing beneficial bacteria. 1). The bacteria in an anaerobic environment are not nearly as robust as those in an aerobic environment (ask for the Herr paper on aerobic POWTS), and will be immediately introduced back into the system as soon as you begin using (flushing water into) the tank again. 2). The benefits listed above far outweigh the removal of the anaerobic bacteria.

Effluent just means the wastewater that has been partially treated in a septic tank, and effluent is the water leaving the septic tank.

An effluent filter typically takes the place of the outlet baffle of a septic tank . The water in the septic tank has to work its way up through the filter to exit the tank. Most effluent filters block particles that are larger than 1/8 inch from getting out of the tank. There are also filters that will filter to 1/16th inch and 1/32nd inch.

In Wisconsin code has required that an effluent filter be part of every POWTS that is installed or replaced since 2000. Current state code requires that particles of 1/8 inch and larger not be allowed out of the septic tank.

Filters do not work too well in a single chamber septic tank. Filters in a single chamber septic tank tend to plug up frequently. Most filters are installed in the second compartment of a two-compartment septic tank, or in a second septic tank. This way the larger solids get a chance to settle out prior to the water going through the filter. The recommendation for filter cleaning is twice per year-once in spring, once in fall.

Some users will not have to clean their filter twice in one year, but it should at least be checked twice per year to
prevent sewage back ups.

The Importance of Cleaning a Filter

As filters accumulate solids they will eventually slow water exiting the tank and in some cases completely prevent water from exiting the tank. As you continue to use water, if the filter is plugged, backups of sewage to the ground surface or back into your house could occur.

It is very important to maintain good filter cleaning practices to prevent backups from occurring .

Effluent Filter FAQs

Q: If a filter could cause a sewage backup, why should I have one?
A: Besides being required, the goal of a filter is to reduce/minimize waterborne solids that are getting out of the septic tank and flowing to the soil component (i.e. seepage bed, mound system, etc.) . These waterborne solids plug the soil pores and will eventually cause system failure (i.e. soil will no longer take water ). Filters are one effort to maximize the longevity of your system.

Q: Do filters have to be replaced?
A: Most good effluent filters are rather robust plastic (think 5 gallon bucket but harder plastic)and should last several to many years, they require routine cleaning, and only in rare instances, replacement.