How often do we need to drain our septic tank?

John Conlin / 24 November 2016

Chartered surveyor John Conlin answers a reader’s query on septic tanks.


We have just moved from town to country and are told that our new home has ‘septic tank’ drainage. How often will it need emptying?


There are no rules or yardsticks when it comes to emptying septic tanks. It depends on usage, tank size and the effectiveness of the discharge soakaway.

I surveyed a house where the owner had forgotten exactly where the septic tank was because he had never needed to empty it in 40 years. In other cases owners routinely empty them annually.

Open the inspection lid every three months. If it is operating well the contents should have a dryish top layer. When this gets near the top of the tank it would be sensible to have it emptied.

For more tips from John Conlin visit the
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