Advice: General

What’s the difference between a cesspool, a septic tank and a sewage treatment plant?

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Briefly, it’s in the different ways in which they handle sewage and wastewater:


A sealed underground tank that simply captures and holds sewage from the property. It does not process, digest or reduce the sewage in any away. It therefore fills up rapidly and needs emptying often — typically at monthly intervals.

Septic tank:

Unlike a cesspool, a septic tank processes sewage by settling out and partially digesting the settled sewage using natural biological processes. It also discharges a liquid effluent into a soakaway system specially created for that purpose. As a result, it needs emptying much less often – typically once a year.

Sewage treatment plant:

Goes a step further than a septic tank by settling out and then treating the sewage via an actively assisted process – typically an electrically driven system involving rotating media discs designed to promote aerobic bacterial digestion. Produces an effluent that can be 95% clean and which can be discharged – with appropriate consents – into a nearby watercourse or specially constructed land drain system.


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