Reduce Drainfield Size With This Passive Treatment System

Enviro-Septic treatment units help an installer design cost-effective systems on space-constrained sites

Reduce Drainfield Size With This Passive Treatment System

Luke Rotti of Rotti and Son on a job site in Templeton, Massachusetts.

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When replacing septic systems for older homes, the Rotti and Son installation company often needs compact drainfield solutions.

In many such cases the company, based in Templeton, Massachusetts, uses Enviro-Septic passive treatment systems from Presby Environmental (owned by Infiltrator Water Technologies), when so directed by design engineers. Co-owner Luke Rotti says the units enable substantial reductions in drainfield size while complying with local and state regulations.

The Enviro-Septic system replaces rock drainfield media with plastic corrugated and perforated pipe units 10 feet long with a 12-inch outside diameter. The pipes are then wrapped with a dense mat of plastic fibers and a geotextile fabric. The assemblies also include snap-lock couplings, offset adapters and end caps.

Once completed, the entire assembly is surrounded with washed ASTM C-33 sand, which enhances the supply of oxygen and facilitates efficient dispersal of treated wastewater. The plastic fibers keep the fabric from pressing against the pipe while providing substantial surface area for bacterial activity. This ensures a sufficient oxygen supply and protects the bacterial treatment surface that forms on the inside of the fabric.

The plastic fiber mat also acts like a filter, stripping out solids from wastewater as it passes through and protecting the bacterial surface from clogging. In addition, skimmer tabs maximize solids retention within the pipe, protecting the fiber mat and geotextile fabric from clogging.

The pipe’s designed ridges create additional surface area and help cool the septic tank effluent. This enhances separation of greases and solids, enabling the system to retain them inside the pipe and fibers so that they do not reach the bacterial treatment surface and do not enter and clog the underlying soil.

The system does not require mechanical devices, replacement media, filters, additives or electricity. The manufacturer notes that while the permissible system size varies from state to state, installers can expect at least a 40% reduction in drainfield size, translating to lower installation costs.


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