Concrete Chambers Versus Enviro-Septic® Systems

Categories: Precast Concrete (1), Septic Systems (8)
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Concrete Chambers VS Enviro-Septic Systems

The Benefits of Each and When One Solution is Better Than the Other

Overview of Concrete Chambers and Enviro-Septic® Systems

This guide to concrete chambers and Enviro-Septic® systems will assist septic system designers and contractors in NH by detailing important differences and uses for each type of leach field structure.

We begin by reviewing descriptions and features of leach fields designed with concrete chambers or Enviro Septic systems.  We then examine how to select the best type of dispersal field based on site conditions and New Hampshire septic system design requirements. Finally, we contrast the features and benefits of concrete leach chambers vs. enviro septic pipe systems by evaluating 8 comparison factors.

As an experienced manufacturer and distributor of wastewater management systems, A.J. Foss serves as a trusted resource for septic system designers and excavation contractors.  We partner with industry professionals to deliver cost-effective, safe, environmentally-friendly septic systems.

A leach field (or drain field or leach drain) is designed to disperse liquid waste from a septic tank.

A leach field helps to remove impurities from septic tank wastewater by filtering the wastewater throughout the field, where natural bacteria can break down impurities and purify it.

Residential septic systems and leach field requirements vary according to property types, locations and site conditions. This article explains the differences between concrete chambers and Enviro-Septic®; two popular types of septic drain field systems for which A.J. Foss manufactures and supplies materials.

What is a Concrete Chamber Leach Field?

Concrete Chamber Leach Field
A leach field with a chamber septic system consists of a series of connected precast concrete chambers. Each concrete leaching chamber efficiently disperses wastewater effluent by filtering it out into the surrounding soil through holes in the sides and bottom of each septic chamber. Naturally occurring microbes in the leach field soil can then treat and purify the effluent.

Concrete leach field chambers are ideal for small lots or properties that require the leach field to be H-20 traffic-rated due to its location in a driveway or parking lot.  Concrete chambers also qualify for a 40% reduction in leach field size compared to a pipe & stone system.  Concrete chambers install faster than enviro septic tubes. Component costs are similar for both systems.

What is an Enviro Septic Leach Field?

Enviro Septic Leach FieldAn Enviro-Septic® system consists of a series of enviro-septic tubes lined with geotextile fabric and coarse fibers.  They work by skimming the waste and mixing air into the filtered waste. This process enables an enviro septic system to purify waste into a cleaner, purer liquid effluent for leach field distribution.

Enviro septic tubes are ideal for waterfront property leach fields, as enviro septic installation is permissible within two feet of the seasonal high water table. (Although recent NH septic system design specifications make this less of a differentiation from Concrete Chamber leach fields.)

Each 10-ft section of enviro septic pipe (or enviro pipe) has a 12-inch outside diameter, and is assembled using snap-lock couplings, offset adapters, PVC piping and end caps.  Thus, enviro septic tubes take longer to install than concrete chambers. Component cost is similar to concrete field chambers, unless the system must be reinforced to accommodate H-20 vehicular loads.

Features of Concrete Chambers Manufactured by AJ Foss

Precast concrete chambers for septic system leach fields provide septic system designers, excavation contractors, and homeowners with several advantages, as outlined below.

8 x 8 Concrete ChambersCost Effective – A precast concrete chamber system has fewer components and typically costs less to purchase and install than other systems.

Strong, Durable and Long Lasting – Concrete increases in strength over time versus high-density polyethylene (plastic) and steel.  The life of precast concrete can exceed 50 years.

Traffic Rated – Strong, durable concrete is H-20 traffic rated to withstand vehicular loads.

Resistant to Buoyancy – Concrete’s specific gravity resists buoyancy better than other materials such as fiberglass and plastic, which require added time and expense to secure.

Fire Resistant and UV Stable; Does Not Degrade from Sunlight Exposure – Concrete leach field chambers do not degrade with sunlight exposure, like some plastic products can.

Environmentally Safe and Natural – Precast concrete is a natural, “green”, locally-made building product that’s manufactured from environmentally safe and natural materials.

Resists Seasonal Weather Conditions – Precast concrete withstands seasonal weather extremes.

Quickly and Easily Installed – A precast chamber type septic system installs quickly with minimal, easy connections and low propensity for damage during the back-fill process.

Minimal Maintenance – Precast concrete for leach fields requires minimal maintenance and no special tools, such as those needed to maintain buoyancy of lighter materials.

This Concrete Leaching Chambers page outlines the features of the five most popular sizes – including the highly sought after 8 x 8 size, in addition to several 4 x 8 versions – as well as concrete chamber size diagrams and PDF drawings of each chamber size.
NH Enviro Septic System Installation

Features of Enviro-Septic® Systems

Presby septic systems are under new ownership.  In 2019, Infiltrator Water Technologies purchased Presby Environmental Inc., manufacturer of Enviro-Septic® products. Infiltrator Water Technologies uses “green” materials produced by its subsidiary, Champion Polymer Recycling, including post-consumer and post-industrial recycled plastics for the manufacture of products at the firm’s ISO 9001-registered manufacturing facility.

Each unit of Enviro-Septic® pipe measures 10 ft long, with a 12-inch outside diameter and 10-inch inside diameter. The enviro septic tube system is assembled with snap-lock couplings, offset adapters, PVC piping and end caps.  Specialized sand must be placed around enviro septic pipe.

A.J. Foss is an experienced, authorized distributor of Enviro-Septic® systems, and maintains an excellent working relationship with the manufacturer.

This Enviro-Septic Systems page further outlines the features of enviro septic pipe and enviro septic system components, as well as links to review PDF files including the Enviro Septic Owner’s Manual and H-10 and H-20 Loading Guidelines for Enviro Septic systems.

New Hampshire Leach Field Design Specifications

The oldest and most common type of septic system is a conventional stone and pipe septic system. It involves digging a series of trenches in the septic field to distribute treated septic effluent.

The length and number of trenches this type of system requires depends on two key property factors: home size (number of bedrooms) and soil percolation rate (measured in minutes per inch). Stone and pipe systems typically last longer than other system types; however, they require a large open area.

Large residential open spaces are becoming scarce in New Hampshire, and many properties are located on smaller lots or near water bodies.  Fortunately, NH residential septic system design specifications allow for smaller leach field sizes (as compared to stone and pipe systems) for small and/or waterfront properties that qualify.

How to Choose a Leach Field System

Guide for NH Designers and Contractors

The best way to select a dispersal field system is to consider the site conditions outlined below.

Ideal Site Conditions for Concrete Leaching Chambers in New Hampshire

Residential site conditions for which a concrete chamber drain field is often specified include:

  • Flat, open area with direct access to the septic tank and leach field
  • Low or average water table
  • Optimal (low) percolation rate, typically between 2 and 10 (minutes per inch)
  • Driveway (or vehicular access) over the leach field
  • Narrow lots with optimal percolation rate

Learn more about percolation rate, and conditions that affect septic system installation, in our article, Septic System Cost: An Installation and Replacement Guide for New Hampshire

Ideal Site Conditions for Enviro Pipe Systems in New Hampshire

Residential site conditions for which an enviro septic system is typically recommended include:

  • Sloping or hillside area with limited access to the septic tank and leach field
  • Higher than average water table
  • ANY soil percolation rate, since perc rate is irrelevant for use of an Enviro-Septic® system
  • No driveway (or vehicular access over dispersal field) required

Benefits of Concrete Leach Chambers Versus Enviro Septic Pipe Systems

H-20 Traffic Loading Rating

Concrete Leach Chambers can be driven over, since precast concrete is H-20 traffic rated.

Enviro Septic Pipe Systems cannot be driven over unless a special fabric and backfill product is used – at an additional cost for components and installation.

Learn more about Design for Vehicular Traffic in this article by the Director of Technical Services of the National Precast Concrete Association.

Allowable Percent of Leach Field Size Reduction Compared to a Pipe and Stone System

In New Hampshire, pipe and stone dispersal fields are the standard by which all other septic system alternatives are compared.  A septic system designer begins any project by considering two key factors about a property – the number of bedrooms (which represents gallons per day of water use), and the soil percolation rate – to determine the leach field size required for a pipe and stone system.

Next, if the designer is considering any other type of system, he or she must follow state regulations regarding permissibility and the allowable drain field square foot size reduction, per technology.

Designers consult the New Hampshire Code of Administrative Rules Table 1016-1, Bed Size for Conventional Stone and Pipe Systems in Square Feet for Varying Loads and Percolation Rates.

This table identifies the conventional bed size, based on perc rate and number of bedrooms of Single-Family and Duplex residences.

Concrete Leach Chambers receive a size reduction of 40% versus traditional pipe and stone systems. Concrete chambers are sized by their footprint, or the total leach field sq. ft.

Enviro Septic Pipe Systems receive a reduction that varies according to installation requirements, and a single-level design calculation, as opposed to a standard reduction. In some cases, the size reduction is up to 60%.  Enviro-septic tubes are 10 feet long and the whole circumference is used to determine the sq. ft. per tube.

Installation Time and Equipment Needed for Septic Chambers versus Enviro Pipe

Concrete Leach Chamber installation is a faster and easier process than enviro septic installation. For example, if 8x8-ft chambers are used, 64 sq. ft. can be installed at a time. Locally-manufactured concrete chambers require setting with heavier equipment that most contractors own.  If a contractor has only a small excavator and cannot set the chambers, then a precast concrete manufacturer such as A.J. Foss can use a crane to set them, provided that there is adequate access to the leach field bed.

Enviro Septic Pipe System installation is a longer and more involved process than chamber type septic systems.  For example, each 10-ft. long enviro septic pipe requires setting and connection. A wooden frame is also commonly constructed and used as a “jig” to prevent enviro tubes from shifting upon backfill. In contrast, heavy and stable concrete chambers do not move once set into place.

Enviro-septic system installation also requires careful phasing to ensure that heavy equipment does not drive over the system throughout the process.  For example, an excavation contractor may need to work the typical steps backward, by first installing the Presby septic system; then the septic tank; then the residential plumbing connections, if access is limited.

Bed Requirements for Leach Field Systems

Concrete Leach Chambers are set on a bed of readily-available ASTM-33 washed concrete sand, and surrounded by 12 inches of septic stone. There are no sourcing restrictions or mandated suppliers for this type of septic sand.

An Enviro-Septic® Pipe System must be placed on a bed of specialized, manufacturer-specified sand that is available only from factory-specified vendors at a few approved locations in NH.  As such, this sand is more difficult to source, and can cost more to purchase and transport to project sites located far from an approved source.

Presby septic systems can fail – and also fail a NH septic system inspection – if non-approved sand is used, or if installation is inadequate (such as improper venting, etc.)

Site Requirements, Including Distance to Seasonal High Water Table (SHWT)

Concrete Leach Chambers:  A new septic system requires that concrete chambers (also called flow diffusers) be located a distance of 4 feet from the seasonal high water table.

A replacement system, however, requires only 2 feet of separation from the SHWT.  Concrete chambers must be set in a flat area, and the septic drain field must be level.

Enviro Septic Pipe Systems:  A new or replacement enviro septic system can be located either 2.5 or 2.0 ft. from the Seasonal High Water Table.

Enviro systems can be placed on multiple-level sites, such as on a slope or hillside.

Cost of Leach Field System Components

The main factors that affect the scope and cost of any type of septic system include

  • The leach field size that the property requires (which is determined by the site’s soil perc rate and number of bedrooms in the residence)
  • The type and amount of required system components, plus any accessories or additional materials needed to install the components
  • Site accessibility, which affects the timing and level of effort to access the site

Concrete Leach Chambers: The number of concrete chambers a leach field design requires is based on the site’s soil percolation rate.  An optimal (lower) perc rate requires fewer chambers to disperse effluent that leaves the septic tank into the leach field.

A flow diffuser septic field can be set onto a sand bed in minutes and does not require assembly components and labor, so it costs less to install than an enviro septic system.

Enviro Septic Pipe Systems: The number of enviro septic tubes required depends on the required size of the leach field.  Originally, Presby septic systems received up to a 65% reduction in leach field size. Today, however, they typically qualify for up to a 50-55% reduction, which decreases their size advantage over concrete chamber systems.  Enviro septic systems also require more installation components and time to install than concrete chambers.

Life Span of Concrete Leach Field Chambers Versus Enviro Septic Tubes

Concrete Leach Chambers typically last 20 to 30 years, when properly maintained*

Enviro Septic Pipe Systems typically last 10 to 20 years, when properly maintained*

*Maintenance factors that affect septic system longevity include:

  • Materials Input – Users of any type of septic system should avoid introducing materials that can be detrimental to a leach field, such as grease, fats, oils, and household cleaners.
  • System Use – Users of any septic system should avoid consistently overloading the septic system with more waste water than the tank and dispersal field are designed to handle.

Reusability of Leach Field System Types

Concrete Leach Chambers:  Concrete chambers are reusable.

Enviro Septic Pipe Systems:  Enviro septic tubes are technically reusable, but most excavation contractors will not handle used tubes because the fabric is saturated with septic wastewater.

In our team’s experience of partnering with septic system designers and excavation contractors, we share a mutual goal of providing proven, long-term septic system solutions for their clients.

That’s why A.J. Foss sells both concrete chambers and Enviro-Septic® systems – among other system types – in order to meet the needs of any septic system project.

Frequently Asked Questions about Chamber Leach Field Systems vs. Enviro-Septic Systems

The number of leaching chambers a property requires correlates directly to site conditions including the bedroom count (which represents gallons-per-day of water used), and the percolation or “perc” rate (which represents the rate of absorbency into the ground) where the septic system is to be located.  It also depends on whether an advanced treatment unit (ATU) will be used, or a conventional septic tank. 10 to 16 is a common range of required leaching chambers.  Septic system designers refer to NH Table 1016-1 to determine the leach field bed size, based on the number of bedrooms and perc rate.

For high water table properties, the ideal type of leach field depends on whether you are installing a new leach field or replacing a failed one.  For a new drain field, an advanced enviro septic system can be sited within 24 inches (2 feet) of the seasonal high water table (SHWT), while new concrete chambers must be sited 48 inches (4 feet) from the SHWT.  However, replacement concrete chambers may be sited 24 inches from the SHWT, which is the same distance requirement as a new advanced enviro septic.

A concrete chamber septic system is typically recommended for properties that require vehicular traffic loading over the leach field.

For a property with limited space, that requires the smallest possible leach field size, an enviro septic system is ideal. This is because the leach field size remains constant, whether the percolation rate ranges from 1-40. For example, the enviro septic system footprint for a three-bedroom home is 384 sq. ft., whether the perc rate is optimal (low) or poor (high).  Conversely, the septic system footprint for pipe and stone or concrete chamber systems can increase or decrease according to the property’s perc rate.

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