Environmental Health
Septic Systems
Operation and Maintenance
  Inspecting Your Septic Tank  
  The Stick Test  l  Step 1 Uncover the Tank  l  Step 2 Measure the Scum  l

Step 3 Measure the Sludge  l  Step 4 Inspect the Baffles  l  Cleanup & Disinfection

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The Stick Test

Woman inspecting septic tankSeptic tanks are mainly settling chambers. They allow time for solids and scum to separate out from wastewater, so clear liquid can safely go to the drainfield. Over time, the scum and sludge layers get thicker, leaving less space and time for the wastewater to settle before passing to the drainfield.

For every gallon entering the tank, one gallon is pushed out into the drainfield. So it is important to keep the level of scum and sludge from building up and nearing the inlet or outlet baffles, where the scum or sludge could plug them up or be carried out to the drainfield.

Diagram of septic tankSeptic tanks should be checked for buildup every 1 to 3 years until you can get on a predictable pumping schedule. Most septic tanks need pumping every 3 to 5 years. How often depends on the size of the tank, the number of people in the household, and the amount and type of solids entering the tank.

You can hire a professional or inspect your septic tank yourself. The "stick test" procedure will guide you through the steps of measuring the amount of scum and sludge in the tank, discovering the working capacity of the tank, and determining whether the tank needs pumping. A more complete inspection includes inspecting the condition of the baffles and the pipe seals into and out of the tank (see Step 4).

Photo of scum and sludge sticksWhat You Need to Do the Stick Test

  • two 10-foot PVC pipes*
  • four end caps*
  • one 90 elbow*
  • PVC cement (blue cement used in rain and wet)
  • two adapters, SxMPT, threaded*
  • one coupler, threaded*
  • two feet of white rag or old towel or old gym sock
  • string or duct tape
  • pencil or waterproof marker
  • rubber gloves
  • disinfecting solution made of 1/4 cup bleach per gallon of water in a bucket
  • plastic bag for disposal of towel, rag/sock, gloves

    *all PVC materials are 1/2-inch Schedule 40 PVC plastic

The scum stick at right is 6 feet long with a 6-inch leg. The sludge stick is two 5-foot sections screwed together. (NOTE: Scum and sludge sticks can be any length up to 10 feet.) For instructions on making the scum and sludge sticks, see Step 2 - Measuring the Scum Level and Step 3 - Measuring the Sludge Level.

Go to Step 1 - Uncover the Tanks

Also see:
Step 2 - Measuring the Scum Level
Step 3 - Measuring the Sludge Level
Step 4 - Inspect the Baffles
Cleanup and Disinfection

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This page last updated: 06/05/18