It was great working with John from Eco-nomic.com on his septic plans website. Here’s a bit about what John does:
The term gravity septic system means that the sewage effluent leaving the septic tank winds up in the drainfield without the help of an electric pump. Septic systems used to be only gravity types, often with tanks and drainfields much deeper in the ground than modern standards will allow.
The first septic system appeared in France in the 1860s. The gravity “system” includes two main parts, a tank and a drainfield to dispose of the sewage. The sewer pipe leaving the building directs the sewage into a hollow concrete box, the septic tank. The septic tank has internal barriers and pipes to prevent “solids” and cooking grease floating in the tank water from entering the drainfield and clogging the soil. Organic solids and cooking greases can build up on the soil interface and cause drainfield “failure” when the soil will no longer absorb water. Owners usually discover failed drainfields when untreated sewage appears on the surface of the ground in the yard. Often a failed drainfield means that the toilets will not flush and drains in the house back up. Failure usually requires building a new drainfield in a new area.
Drainfields contain two or more equal length trenches in the yard beyond the tank. This is where the “treatment” of the sewage happens. The trenches are three feet wide, and up to a hundred feet long. Excavators must build the trenches at dead level. Trenches traditionally contain drainrock, a washed stone of uniform size, a little smaller than golf balls. Sewage effluent from the tank flows out into the drainfield into a level four-inch diameter plastic pipe with dime sized holes along both sides that (in theory) distribute the effluent evenly throughout the entire drainfield into the void spaces between the drainrock. Modern drainfields now can be constructed without drainrock. Instead, they utilize arch-shaped plastic vaults with open bottoms that provide a much larger storage space underground in the drainfield for sewage effluent as it slowly soaks into the soil below.
Read more about Eco-nomic’s Gravity Septic System here.
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