inlet baffle

 

Where a replacement PVC plastic septic tank tee is installed into a steel or concrete septic tank, the outlet or inlet tee is a standard pipe tee, typically of the same diameter as the incoming sewer line, placed at the inlet of a septic tank to prevent the inlet sewer line from being clogged by floating scum and waste in the tank (resulting in a blocked septic system).

On the inlet side the septic tank baffle is intended to permit waste to enter the tank, but to avoid clogging of the tank inlet. The septic tank inlet baffle accomplishes this job by blocking the floating scum layer, a thick layer of debris that forms naturally at the top of a working septic tank, from blocking the tank inlet pipe.

At SEPTIC TANK BAFFLES we describe inspecting the condition of the septic tank baffles when the tank access ports have been opened, for example when the septic tank is about to be pumped.The septic tank inlet baffle also reduces the movement of gases from the septic tank backwards into the building that it serves. Any gases that do escape the tank in this direction should be venting above the building's roof through its plumbing vent system, provided that system is itself correctly installed.

                                           outlet baffle

 

The septic tank outlet tee blocks floating scum and sewage from flowing out of the tank where it would rapidly clog the drain field and effluent piping.

Located on the septic tank's outlet end where the tank is connected to piping intended to conduct clarified septic effluent to the absorption system (drainfield), the septic tank baffle or tee, also called a Gas Baffle in some literature or regulations, keeps solid waste and gas bubbles away from the septic tank outlet, thereby reducing the carry over of solid particles from the septic tank.

This job is critical since sending solid waste out of the septic tank into the drainfield (absorption area) will certainly lead to clogging of the soils there, shortening the life of the drainfield. We describe this septic tank baffle or tee inspection in more detail at SEPTIC TANK BAFFLES.

                               fliters

  

To add protection for the septic absorption system, add a septic effluent or gray water filter at the septic tank outlet tee. The sketch at page top (US EPA) shows a filter installed at a septic tank outlet.

The photo at left shows a simple filter which is installed inside the outlet tee of a septic tank.

If there is no room in the tank to install such a filter, a small chamber and filter can be installed outside of the septic tank but upstream from the drainfield - just like our septic graywater basin and filter shown in the previous sketch..

Although most grease or large solids entering the septic tank are intended to be retained there where they are reduced to floating scum at the top of the tank or settled sludge at the tank bottom. However septic tank effluent also contains suspended solids, smaller particles of debris which, as they pass out to the soil absorption system, or drainfield, speed the clogging of the absorption system and thus shorten its life.

By trapping more of the suspended solids in septic effluent we pass clarified septic effluent to the absorption system, extending its life. Don't worry about starving the biomat by filtering the septic effluent. There are still plenty of nutrients in the effluent passing into the absorption system.

A number of companies sell these devices which will add life to your drainfield by reducing the level of suspended solids flowing out of the tank. If you buy a septic tank outlet filter you'll see that the filter product will typically be of about the dimensions of the outlet tee I cited above, or perhaps an inch or two deeper.

See the links below for more information about septic filters and septic media filter systems.