What Is a Clarifier in an Aerobic Septic System?
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Quick answer
A clarifier is the quiet settling chamber in an aerobic septic tank. After the air pump treats wastewater, the water rests in the clarifier so solids sink out before the cleaner water moves on to the pump tank or dispersal area. A clogged or overloaded clarifier can send solids downstream.
Most people have never heard the word clarifier, yet it is one of the chambers that decides how clean the water leaving an aerobic septic system really is. If your system has an aerobic treatment unit, it almost certainly has one.
What does a clarifier do?
Inside an aerobic tank, the aeration chamber keeps water churning so oxygen-loving bacteria can break waste down. That churning also keeps tiny particles suspended. The clarifier is the calm chamber that follows. Water flows in slowly, the particles settle to the bottom, and the clearer water at the top moves on to the next stage.
Without that rest period, the water would carry too many solids toward the pump, the spray heads or the drip lines, where small openings clog easily.
Where does the clarifier sit in the system?
- Wastewater enters the first tank, where solids settle and begin to break down.
- It flows to the aeration chamber, where an aerator supplies oxygen.
- It then moves to the clarifier to settle.
- From there it passes through an effluent filter and on to the pump tank or disinfection step.
The exact layout depends on the manufacturer. In some units the clarifier is a separate tank; in others it is a section inside a single tank. A technician can show you which you have.
What problems can a clarifier have?
- Too many solids. Heavy laundry days, a garbage disposal or a tank that is overdue for pumping can overload the settling chamber.
- Bacteria upset. Large amounts of bleach, harsh cleaners or medications can disturb the treatment before the clarifier.
- Stopped aeration. If the air pump fails, treatment stops, and the clarifier receives water it cannot clean up.
- Cloudy or smelly water. A technician looking into the chamber can often see these signs right away.
How do you keep a clarifier working?
Mostly by keeping everything upstream healthy: a running aerator, regular pumping, sensible water use and a clean filter. Spread laundry across the week, keep wipes and grease out of the drains, and keep to your maintenance schedule. Our guide on what can go into an aerobic septic system covers the details.
Texas generally requires a maintenance contract on aerobic systems, at least for the first two years. Checking the clarifier is part of a normal service visit. See septic maintenance or aerobic septic service, or call 832-789-5357.
Related septic terms
Quick questions and answers
- Is a clarifier the same as a septic tank?
No. A conventional septic tank is a single settling tank. A clarifier is one chamber in an aerobic system that settles solids after the water has been aerated.
- Do all aerobic systems have a clarifier?
Most do, though the design varies by manufacturer. Some units use a separate tank and others build the clarifier into one tank.
- Can I clean a clarifier myself?
No. It holds untreated wastewater and the gases in a tank can be dangerous. Leave inspection and cleaning to a trained technician.
Related guides and services
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