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Gravel less effluent disposal septic system - image of the gravelless chamber system design is courtesy US EPA, originally from National Small Flows ClearinghouseGravelless Septic System Design Specifications
Septic Leaching Chamber Site Requirements, Design Criteria, & Construction Details

Gravelless septic drainfield site requirements:

This article explains the site requirements, design criteria, and construction details of a gravelless or "no gravel" or "no rock" septic drainfield systems, offering installation specifications.

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Site Requirements & Design Criteria for Gravelless Septic Absorption Systems

Gravel less effluent disposal septic system - Chamber system - image courtesy US EPA, originally from National Small Flows Clearinghouse

Drainfields, also called leach fields, absorption beds, soil absorption systems, and leaching beds, perform the functions of septic effluent treatment and disposal in onsite wastewater treatment systems, conventionally called "septic systems".

Typical gravelless septic systems use a plastic chamber, a geotextile-wrapped pipe, or a polystyrene-wrapped pipe to distribute effluent into the soil.

The necessary soil absorption area is provided by the perforated surface of the gravelless septic system components (or by soil at the bottom of a chamber) themselves rather than by the gravel and trench walls of a conventional septic drainfield.

Site Requirements for no-rock chamber or textile wrapped septic effluent disposal systems: These systems shall be used on sites that have been classified as having a design percolation rate of one to 45 minutes per inch, and meet the vertical and horizontal separation distances in Table 2 (of the New York State Standard - for example) shown in 75-A.4 Soil and site appraisal for Septic Systems.(2)

Chamber systems provided by Infiltrator Inc. (links below) have been approved for use in some states, including New York, at perc rates up to 60 minutes/inch, and in some other states, at percs up to 120 minutes/inch. Approval letters are available from that company.

Design criteria for no-rock chamber or textile wrapped septic effluent disposal systems: : The local health department having jurisdiction shall be contacted prior to construction regarding the acceptability of specific products for use as a gravelless distribution system. (3)

As we described above when discussing Geotextile-Wrapped Perforated Pipe systems for onsite wastewater treatment and disposal, the total lot area in square feet which is required for a given alternative treatment system will vary not only depending on the anticipated daily flow, flow rates, soil and site conditions, but also on what spacing requirements the local or state code officials will require.

So although a number of alternative treatment systems including these gravelless methods are capable of working in a smaller total square foot area than a conventional drain field, depending on what the local authorities require in spacing, more area may be required than the minimum.

For example, many states require that space be set aside to allow for future absorption line replacement in between the planned lines.

Construction Specifications for gravelless septic absorption systems

Gravelless distribution systems shall be installed in conformance with the manufacturer's instructions because of the proprietary design of some products.(4) The length, width, and depth of the required excavation will vary by individual product.

The essential difference between a gravelless wastewater treatment system and a conventional perforated-pipe and gravel-trench drainfield is the use of a special product to distribute and release effluent (sketches above) and the absence of gravel in the trench where the distribution system is buried.

The special gravelless products used are designed to avoid soil-clogging right at their surface or they would have a short life.

This concern is addressed by use of special materials (such as geotextiles) which resist soil clogging, and by a design that provides an adequate total area in square feet for soil contact.

Each product manufacturer should be expected to provide an installation manual for the product that you are going to use. The list below is generic and incomplete as site specific and product specific details can't be provided here.

Chamber Septic - No-Rock Septic Design Critera, Guides, Specifications

Infiltrator Systems' Arc 24 no-rock chamber system septic product - cited & discussed at InspectApedia.com

Consultants or suppliers in this field can be listed at our alternative septic designers page at no charge by contacting me.

Gravelless Septic Design using Poly-Wrapped Pipe

While polyethylene wrapped or peforated-plastic-wrapped plastic pipe is discussed in older no-rock septic system design manuals, the use of poly-wrapped pipe for gravel-less septic effluent disposal has, in our OPINION, been eclipsed by the use of geotextile-wrapped pipe instead.

As of May 2020 it was difficult to even find a vendor selling this product type.

Please see NO-ROCK SEPTIC GEOTEXTILE-WRAPPED PIPE

InspectApedia.com has no financial or other relationship with any suppliers listed at our website and we do not endorse specific products. No fees or costs are involved in product source listings. CONTACT us to add information.


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