Understanding Your Septic System

Understanding Your Septic System

Most Frequently Asked Questions and Answers

1. Question: Should I put a cake of yeast in my septic tank?

Answer: No! As long as human and kitchen waste continue to be flushed and drained into the septic tank, nothing else need be added. Yeast is of no value.

2. Question: Do I need to add bacteria to my septic tank after it is cleaned?

Answer: NO! The human waste from your body will provide all the bacteria necessary.

3. Question: Can adding enzymes repair a clogged drainfield?

Answer: NO. While some contractors continue to advertise enzymes and chemical treatment to revitalize a drainfield, there is no conclusive data to support their effectiveness.

4. Question: How often should I have my septic tank pumped and cleaned?

Answer: The intervals vary from home to home, depending on system size and

number of people using the system. A septic tank should be opened and inspected every one to three years by a qualified septic tank contractor. They can determine whether it needs cleaning by viewing the condition of the tank. (Editor’s note- Peace of mind comes with regular cleaning every other year!)

5. Question: Is it all right to flush sanitary napkins or tampons down a commode serviced by a septic tank?

Answer: NO. Those products are made of cellulose, a non-biodegradable material (the bacteria in the tank cannot work on this type of material). As a matter of fact, the less paper of any kind flushed down the commode, the better.

6. Question: Is it OK to have a garbage disposal in a kitchen that is connected to a septic tank?

Answer: YES, BUT… extreme care should be exercised not to allow grease or non-biodegradable products to get into the disposal system. The septic tank should be cleaned at least annually if a garbage disposal system is in place. NEVER ALLOW GREASE, COOKING FATS, GRISTLE, ETC. TO GO DOWN THE SINK DRAIN OR THROUGH THE GARBAGE DISPOSAL. SAVE THE FAT IN JARS OR CANS AND PUT IT IN THE GARBAGE CAN OUTSIDE.

Source: MinnesotaOn-Site Sewage Treatment Contractors Assn. “The Magic Box, Understanding Your Septic System


Grease is the number one factor causing trouble in septic tanks and drainfields. For one thing, the type of bacteria that lives, eats and multiplies in septic tanks does not thrive in solidified grease.

For another thing, all animal fats congeal or solidify at room temperature. You probably have noticed that after leaving a pan on a stove temporarily after frying bacon, hamburgers, etc. that as soon as the fat remaining in the pan cools, it becomes a grey, solid mass.

This is the very same thing that happens when the leftover fat is poured down the sink drain or into the garbage disposal. It begins to congeal in the sewer line on the way to the tank and a major portion of it forms a big, solid chunk in the tank.

After successive deposits of grease over a period of months, the sewer line passage becomes constricted, if not closed up completely, and the tank now contains a tremendous mass of solid fat that cannot b e converted by bacterial action. To make matters worse, drainage down sinks and commodes within the house becomes slower. Suspecting that “the pipes are clogged” homeowners sometimes use one of the commercial preparations in crystal powder or liquid form with a strong acid base.

This treatment may or may not eat a temporary narrow opening in the sewer pipe, but when the strong chemical gets into the septic tank, it promptly kills what few bacteria are left, attempting to survive on the small amount of sewage not completely wrapped in solid grease.

The damage has now become two-fold. Chemical action has died in the tank, obstructing both the inlet and the outlet. Water can no longer get into the drainfield, which is ruined by the grease, and no new sewage can flow into the tank.


Sluggishness when flushing toilets.
Any plumbing backups.
Gurgling sounds in the plumbing.
Grass in the yard growing faster and greener in one particular area.
Ground mushy underfoot.
Obnoxious odors inside.
Low spots beginning to appear in the yard, whether or not any of the above symptoms have occurred.
Mrs. Murphey’s Law: The probability of a septic system plugging and backing up into the house is directly proportional to amount of company visiting at any given time.

Source: MinnesotaOn-Site Sewage Treatment Contractors Assn. “The Magic Box, Understanding Your Septic System