Posted by Dennis Showers, owner Showers Plumbing (formally Jiffy Jet Plumbing).

Every week or so I get calls from customers and potential customers asking about their septic tank and how it works.

I Like to use a 1250 gallon, two compartment septic tank. This will not be the right size for every need, but makes a great example.

It is 109 inches long by 68 wide and approximately 78 inches tall. The inlet hole for the waste water and material is 64 inches’ center of the hole up from the bottom of the tank. A 4-inch drain pipe goes through it with a “T” pipe glued to it on the inside of it. The “T” will have 4 in pipe approximately 18 inches long going vertical down to the middle of the tank. The outlet hole is at the other end of the tank placed 4-inches lower with a 14-inch down-pipe again.

The reason for the inlet and outlet pipe to be down is when the waste water and material full the tank to a working level and the decomposing get started. When that process gets started the sludge is heaver and sinks to the bottom of the tank. The solids or lighter and they rise to the top of the water and it pushes the Liquid down with its weight as it builds up in mass .

The sludge also builds up from the bottom of the tank. I call it one third one third and one third. With the down pipes on the inlet it lets the waste go to the middle of the tank and the decomposing gets to work. That proses is done in the first compartment. The liquid flows through to the second compartment and exits out of the outlet end and hole of the tank.

On new construction we install Bio mat filters they have to be pulled out and cleaned some times between pumping. The filters keep the very small particle from going out to the lateral lines and plugging up small pores that are in the soil witch causes a system  failure. The bio Mat filters catch approximately eighty five to ninety percent of outgoing material and that makes lateral lines last much longer.

Most older tanks can have A bio mat filter installed in them also.        
The tanks have baffle in it approximately two thirds of the tank is the first compartment. The second one is about one third of the tank. They are made in different styles depending on the company that makes them. The one that I like best have four to six in holes in them spaced about half way down from the top of the tank. The very bottom of the baffle is raised about three inches off the flour. This lets the liquid flow between both compartments to start with when it is fulling up with dirty water and waste material. While the tank is fulling up to its working level decomposing separation of the solids are started and will keep on working as long as it is being used.

One more thing on the tank it will have two risers on top of it coming out of the ground for inspection, for pumping, and for cleaning the bio mat filter.

Now getting in to usage of the tank.  Do not use any type of products that are suppose to keep your solids and sludge in a lickwood  stage all the time. That proses completely Mess up the decomposing proses in the tank. In this case you have to let mother nature run its course on its own with out any out side help and it will work grate: Food garbage is a no no. It does not decompose right and will full up your septic tank a lot faster. Do not clean your paint brushes. Do not pour paint thinner down the drain. Do not dump medicine down the drain it well kill the decomposing bacteria in the septic tank. Do not pour car gas; diesel fuel; carburetor cleaner down your drain. Use bleach sparingly.

For keeping your tank for very long life pump it every two years even if you don’t think it needs done.

Enjoy the use of your septic tank.