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EPA Sketch of an aerobic septic tank design using an aspirated mixer in the treatment tank Alternative Septic System Designs
Septic systems for wet, steep, rocky, small, poor percolation sites

Guide to alternative septic system designs:

This article provides a master list (links at the ARTICLE INDEX the bottom of this article ) of all alternative septic system designs for difficult building sites such as wet sites, steep sites, rocky sites, limited space, bad soils with no percolation or sandy soils with too fast percolation, sites close to a lake, river or stream, and other difficult site conditions.

We provide detailed articles about each alternative septic system design choice, listing its features, design requirements, inspection details, maintenance needs, product sources. We include links to septic design engineers, advanced septic system products and septic design books and building codes. This document is a chapter provides in our Septic Systems Online Book.

Examples of advanced septic designs discussed in this article series include aerobic septic systems, chemical, composting, incinerating & waterless toilets, evaporation-transpiration (ET) septic systems, septic media filters, greywater systems, holding tank septic systems, mound septics, peat filter septics, raised bed septics, pressure dosing septic systems, sand bed filters, peat beds, constructed wetlands, wastewater lagoons, constructed wetlands, and septic disinfection systems.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Alternative Septic System Designs: Onsite Wastewater Treatment Methods for Difficult Sites

Sketch of a Septic Mound System using a pumping stationThis article describes just about every type of alternative septic system design and provides links to detailed descriptions of these designs for onsite wastewater treatment.

"Septic System Alternative Designs" refers to any onsite wastewater disposal method other than the widely used conventional septic tank and leach field. In the U.S. most states require that an "alternative septic system" be designed by a professional and submitted to the local health department for approval.

Sketch: septic mound system design. [Click to enlarge any image]

Alternative onsite wastewater disposal systems can reduce the soil absorption area or leach field size requirement substantially and can in fact in some cases reduce the needed area to zero. For problem sites where space or soil conditions make it difficult to install a conventional leach field or where an existing septic system has failed, these designs are very important alternatives.

The alternative septic system designer conducts the site and soil inspection and testing, prepares the system design and installation plan, supervises the septic system construction, and certifies that the system was installed as designed.

Alternative septic system designs are used for new or replacement septic systems on difficult sites where soil conditions (such as a rocky site, limited soil percolation rate, or high ground water level), or other terrain conditions (such as limited space for a septic system or steeply sloped sites) do not permit the installation of a conventional septic tank and drainfield system.

Examples of site conditions that lead to consideration of an alternative septic design include:

8 General Categories of Onsite Residential Wastewater Treatment Systems

Because various texts provide so many different views of categorizing wastewater systems, I've made this simple list which groups wastewater treatment systems into a few major categories:

[Readers should see our Master List of Septic System Types or our list of alternative septic system designs and products in the links at the left of these pages.]

  1. Conventional Septic Tank and Drainfields

    in native soils for effluent absorption and treatment. Up to 45% of effluent treatment, often less, occurs in the septic tank, the remainder occurring in the drainfield. Some "advanced" septic system designs may be simple modifications to a conventional septic tank and leachfield, such

    as ALTERNATING BED SEPTIC SYSTEMS.
  2. Raised Bed and Septic Mound systems

    which take a similar approach as conventional systems cited above, but which require extra steps of soil preparation or the necessity to bring in fill to treat effluent. A common raised bed design is the sand-lined filter bed septic system.

    See MOUND SEPTIC SYSTEMS
    and

    see  RAISED BED SEPTIC SYSTEMS
  3. Advanced Material Media Filtration systems

    (sand beds, filter beds, peat filters, synthetic textile filters, rotating biological contractor systems, trickling filters, foam media filters including above-ground self-contained systems).

    See MEDIA FILTER SEPTIC SYSTEMS
  4. Aerobic Septic Systems or ATUs,

    which insert additional oxygen into and agitate sewage in the primary treatment tank

    See AEROBIC SEPTIC SYSTEMS, ATUs
  5. Packaged septic mini treatment plants

    or centralized septic designs or STEP systems - a small onsite wastewater treatment plant can be sized and have capacity for individual homes or for large commercial facilities.

    See details at SEWAGE TREATMENT PLANTS, RESIDENTIAL
  6. Wetlands and Constructed Wetlands

    for sewage or effluent treatment. This category may also include greenhouse treatment systems or other methods involving the use of constructed or natural water/land formations. Also

    see LAGOON SEPTIC SYSTEMS
  7. Disinfection Systems

    which perform a final treatment of effluent by use of disinfectant chemicals (chlorine) or perhaps UV light so that effluent can be discharged to the surface or to ground water or even streams and waterways. Also

    see AEROBIC SEPTIC SYSTEMS, ATUs
  8. Waterless and Low-Water and Greywater-Separation systems,

    which may not really treat effluent, may not discharge anything into the environment, but which form another set of alternative designs where water supply or land use restrictions mean that a conventional system is not permitted. Examples include composting toilets, incinerating toilets, chemical toilets, and graywater systems.

    See GREYWATER SYSTEMS

    and ALTERNATIVE & WATERLESS TOILETS.

    See EVAPORATION-TRANSPIRATION SEPTIC SYSTEMS for wastewater treatment and disposal in areas where there is no electrical power and limited or no place for effluent disposal.

Our Master List of Septic System and Wastewater Treatment Alternative Designs

below offers a complete list of alternative septic system designs and major septic system component designs along with a description of each septic system/onsite wastewater treatment approach. For each system we link to articles providing more in-depth design, installation, repair, inspection, maintenance and product source information.

Levels of Wastewater Treatment - How Sanitary is the Final Effluent?

In case the above list of wastewater treatment categories is not enough, there are also various levels of degree of treatment of septic effluent achieved by different versions of these systems, by natural wetlands septic systems, or by use of septic effluent disinfection systems.

For example, you may read about more than one type of gravity dosing or pressure-dosing sand filter beds system which look a lot alike but which achieve different degrees of effluent treatment.

Jantrania (see Alternative Septic Designers) describes eleven Onsite Wastewater Treatment Types in a confusing list (Table 1.3 in his text) since the same type of system may appear more than once (drainfields) depending on the level of treatment achieved by a specific implementation.

In the same text the author proposes a Pollution Scale numbered from 0 Drinking Water) to 10 (Sewage). (p.36). An overall sewage treatment level of 50% would be 5.0 on this scale, and a treatment level of 100% would mean that the output of the system was equivalent to drinking water in purity.

Because over time the concentration of contaminants in incoming sewage and wastewater varies by type of use, level of building occupancy, changing soil moisture and temperature, and other factors, it is risky to assume that a regulation or a septic system design level requiring or claiming 90% treatment (pollution scale 1.0) is always producing effluent treated to exactly that level.

Awareness of the variation in level of contaminants in sewage arriving at a treatment system, as well as awareness of variations in site conditions (level of ground water, temperature, frequency of inspection and maintenance) is behind the very conservative standards adopted by many health departments regulating septic system installations.

The terms percentage of treatment and level of treatment of sewage or wastewater are used in different and perhaps confusing ways. A writer may say that "45% of the effluent treatment occurs in the septic tank".

I take this to mean that whatever the overall or final level of wastewater treatment that the whole system is going to provide, from input to the system to final discharge of effluent into the environment, 45% of it is occurring inside the septic tank. This does not necessarily mean that the effluent discharged from the septic tank is 45% of the way along the pollution scale or nearly half way to being pure drinking water.

The term "level of treatment" should be reserved to mean the overall or final degree of purity of the effluent which is discharged to the environment.

Sewage contaminants- what's in sewage, and typical sewage contaminant levels are discussed in more detail

at SEPTIC SYSTEM CONTAMINANTS

General Categories of Wastewater Dispersal Methods

Adding to the complexity of what to call various septic systems, there are also categories of methods of septic effluent dispersal (to the final treatment and soil absorption or other effluent disposal system) such as:

  1. Gravity-Fed Perforated Pipe in Gravel-Filled Trenches:

    these are conventional gravity-fed drainfields, using gravity to permit wastewater to flow from the septic tank to the absorption system or drainfield. Wastewater moves out of the septic tank to the drain field by gravity in response to and equal in volume to new waste entering the septic tank. The absorption system consists of perforated pipes in gravity-filled trenches dug into native soils.

  2. Drip or Spray systems

    which may disperse effluent above or below ground.

  3. Gravity Dosing systems,

    which distribute wastewater to the drain field in irregular batches or "doses", permitting the absorption system to rest and recover between doses.

  4. Pressure Dosing

    effluent dispersal methods for septic effluent handling such as sprinkler dispersal, and intermittent effluent dosing systems which using pressure dosing by pressure manifold, rigid pipe systems, or pressurized drip irrigation systems

An individual septic system design may use a combination of these methods to treat, disperse, and dispose of septic effluent. For example, a sand filter bed septic system might be fed by gravity, by a gravity-operated dosing system, or by a pump operated pressure dosing system.

Keeping these types of of septic systems

see details at TREATMENT METHODS

and keeping these types of wastewater dispersal systems

see details at DISPOSAL METODS

in mind when reviewing various off-the-shelf packaged septic systems or wastewater treatment systems with interesting but non-descriptive names (like the "magic bullet treatment box") will help you to understand the general approach which has been taken in any specific case and will help you choose among alternative septic system designs and products.

Further reading will be needed to understand the installation cost, maintenance cost, and level of management required of each type of septic system. I collect and publish here additional details on alternative septic system design, installation costs, and maintenance costs.

Links at the end of this article and most of our septic information website pages offer descriptions, design suggestions, product sources for each of these septic system types.

Jantrania (see Alternative Septic Designers) sorts alternative or advanced onsite wastewater treatment systems into five major groups: aerobic septic effluent. treatment systems, media filters, natural systems such as wetlands, waterless toilet systems, and disinfection systems.

Here, however, our list of septic system designs and effluent. treatment alternatives is organized alphabetically and includes not only alternative methods of primary treatment but also methods of effluent final treatment, dispersal, and disposal. Conventional gravity septic tank and effluent drain field systems (Jantrania/Gross wastewater system type I) are discussed at the "Septic Systems Home" and "Septic Design Basics" links at the left of these pages.

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

Alternative Designs for Onsite Sewage Treatment - References

 

 




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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2022-11-25 by InspectApedia (Editor)

@Andrew Meppen,

Thank you for the nice comment; we work hard to provide accurate, un-biased information and we welcome questions, criticism, content suggestions. We are happy to cite and provide contact information for people who contribute technical content, research, suggestions.

On 2022-11-25 by Andrew Meppen

Installer from Northwest Arkansas. Glad to stumble across your site. It seems very in depth and informative.

On 2022-08-28 by InspectApedia (Editor)

@InspectApedia (Editor),

Look at raised bed septics, mound septics, and packaged aboveground septic system designs that you will find in the article index.

On 2022-08-28 by InspectApedia (Editor)

Re-posting without Kamran Choudhri's improper advertising link

kamran (no email)

COMMENT: looking for alternatives thoe of septic ta ks and leach fiedk designed method with calculate steps for community development in water logged area

On 2022-08-28 by Kamran Choudhri

after disk disinfectant with chlorine dosing what whats kind of trees plant can be used in leach fields to speed up evapktransoiartiin with plants roots invasion control into leach fuled

On 2021-07-07 by danjoefriedman (mod)

@Jay,

Sorry but in order to protect reader trust, insptctApedia doesn't sell anything. No products and no services.

However at the experts directory that you can find at page top or locally you should be able to find a septic design expert who can help you decide if there are any workable options for your property.

On 2021-07-06 by Jay

There is a septic tank but no drain field.the county took the drain field when they widened the road.Do you offer anything the county permits office will approve?

On 2021-05-16 by danjoefriedman (mod) - excess water in drainfield

@Liz, yes there are solutions for wetland like yours;

In the article above on this page, find the live links for two septic designs in this text

Raised Bed and Septic Mound systems which take a similar approach as conventional systems cited above, but which require extra steps of soil preparation or the necessity to bring in fill to treat effluent. A common raised bed design is the sand-lined filter bed septic system.

See MOUND SEPTIC SYSTEMS
and

see RAISED BED SEPTIC SYSTEMS

On 2021-05-16 by Liz

My land is lower than those on each side of me so in hard rain and snow melt I get excess water in my drainage field and my septic system gets overly filled with water. What, if any system is there that would ease or cure this problem for me.

On 2021-02-20 by danjoefriedman (mod) - above-ground effluent spray disposal system

@Robert,

Take a look at the aerobic septic systems in the ARTICLE INDEX on this page; some of these use an above-ground effluent spray disposal system.

Hire a local septic design engineer who will know which alternative septic systems your local health officials will approve.

On 2021-02-20 by Robert

Looking for a system for residential use in poor soil conditions that can drain effluent waste water on top of ground with no drain field required

On 2022-11-25 by Andrew Meppen

@Scotty, depends on how the soils drain/ evaporate.

Level is fine unless there is not 8" of fall from the sewer stubout of the house to the position of the distribution device in which case it would need to be pumped to the lateral field. Gravel in the ground is good, more surface area for effluent to disperse. Mostly worried about high clay content or mineral deposits that indicate a high water table.

On 2020-09-26 by danjoefriedman (mod)

In the article index, you will find articles on drain field size determination

On 2020-09-25 by Scotty

My question is how many total footage is need in a 1000 gal septic tank?

I’m sorry if the ground is good with no gravel and site is level

On 2020-09-08 - by (mod) - can I put underground drainfield right where I need to put an addition?

Norma

Thank you for the important and helpful question. Building over a drain field, even on stilts, generally a bad idea. During construction of your addition the risk is driving equipment over or doing other things over the drain field that damages piping or compressor oil, ruining the field. It's all so of course possibility of odors for of interfering with transpiration or evaporation of a float.

Over a longer-term you also face the problem of how you will ever repair or replace the drain field in that area. If your property has adequate space you may be able to relocate the drain field. How to be a better option if you've got to build in the present dream field area.

On 2020-09-08 by Norma Miller

I have an underground drainfield right where I need to put an addition. What will I need to do? Also if I have to make changes could one possibly be to put the addition on a beam? Where the addition starts and ends lenghtwise, I could put that on pillars and go right past the field.

On 2020-07-20 - by (mod) - septic not possible on sheer rock face cliff over ocean

septic system for a sheer rock face cliff over the ocean?

Yam

You don't give your country and city of location but in most of the world is illegal and in all of the world it is a very bad idea to Simply dump raw sewage into the ocean much less down a rock cliff face.

So there's no septic system that would permit that.

However if you check with your local building department, Health Department or septic Authority, you may find that a packaged wastewater treatment system that produces adequately clean treated and disinfected water might be permitted, depending on where you live.

From your photo, I cannot imagine any conventional septic system that would be safe and legal along what amounts to a sheer rock face. However you may be able to install an aboveground septic wastewater mini-treatment-plant that discharges clean or disinfected water only, and that may be approved by your local officials.

On 2020-07-20 by yam

Hello,
I am building a house on this hillside. There is enough space for a septic tank but no where to drain it except for the ocean. Which would be the best system to use. Please help.
Thanks,
Yam
Septic design for sheer rock face over the oceran (C) InspectApedia.com Yam

On 2020-06-23 - by (mod) -

Karen

You want to search for septic design engineers or septic contractors who can do a soil percolation test and who can review the plans for your present system. Call some of the local engineering firms in Davie County NC or see if your local department of health can identify someone with whom they've worked.

Public health department in Mocksville, North Carolina
Address: 210 Hospital St, Mocksville, NC 27028
Phone: (336) 753-6750

On 2020-06-09 by Karen Powers

I just had a new drainfield installed and it doesnt work. The water doesn't drain into the ground fast enough. I need a name of someone who could do a study of my land and give me an alternate system that would work. I live in Davie County North Carolina . Thanks for any help.

On 2019-12-19 by niall mackay

is it possible to locate a septic tank on a lot and have the effulent water only go to a municipal system. and having the tank pumped on a regular bases. thus not needing a tile field.

On 2019-11-18 by (mod) - piping wastewater across a creek

Jackie:

Indeed even that outhouse is probably too close to the creek by today's standards;

The "best design" isn't a single right answer for piping wastewater across a creek; any such piping will have to be properly pitched, accessible for cleaning, and deep enough not to become exposed by runoff; but the real question isn't the piping it's the destination of that piping;

Just what sort of septic tank and absorption field will work at your property depends on a number of factors like the area available, its location, slope, distances to waterways and wells and property boundaries etc., AND importantly, on the soil depth and type and percolation rate.

All of that griping leads to the need to have a septic engineer on site to inspect, soil-perc-test, review what the local officials will permit, and then propose a system. That may be where your $35K came from?

On 2019-11-18 by Jackie

I have old 700 sq' cabin 8000' elevation with outhouse. steep hill meets back of cabin. front of cabin is 50' from small creek. soil varies with clay, black dirt, and sparse areas of decomposing granite. told system must pipe across creek. what are best designs for this setting? looking at $35,000 as it stands. Thanks.

On 2019-06-06 by danjoefriedman (mod) - ocean front septic system on sand and coral

Douglas

There's a variety of effluent pumps available capable of lifting to the height that you require, although it might be less expensive to use more than one station, i.e. an intermediate pump boost station. Just check with your local septic supplier.

On 2019-06-05 2 by Douglas Barker

We have a ocean front beach that is 600 feet below flat land that can be used as a septic tank location and leak field. We cannot put waste into the ocean or the beach land which is sand and coral rock.

Do you have any idea how we can pump the effluent up the steep hill it's 55% slope on average and runs for 1800 feet

Or us there a safe marine alternative there are planned rest rooms for a beach club that will have a maximum of 100 visitors a day. And as low as 10

On 2019-05-22 - by (mod) - how much can a septic tank be out of level

Thanks for the interesting question, Laura; how much can a septic tank be out of level.

My general answer is ... it depends on out of level in what direction, but generally, not much.

For example, the height of the bottom of the inlet pipe opening to the septic tank might be 4-6" above the bottom of the tank's outlet opening. If the tank is tipped to reverse or lose that difference in elevation the septic tank won't work, will clog, and back-up into the building.

If the septic tank is a little tipped to one side, not fouling up the inlet and outlet heights, it might work. The question is - how much, on what axis, and in what septic tank design.

These are questions that can be answered authoritatively by the septic engineer who would have designed the system for a rocky site. Let me know what she tells you.

On 2019-05-22 by Laura Stone

My husband and I are considering the purchase of a building lot that is located on a mountain bluff, therefore very rocky terrain. The owners of this lot have already had installed a low pressure septic system.

The reason I write is to ask if the position of the tanks is to be installed straight into the ground or can they be tilted to their side if installation is difficult due to all the rock? There is alot of rock piled up around what appears to be two or three green, plastic tanks...but they are tilted over at an angle...not level and sitting straight up.

So the caps are somewhat over on the side. It looks like this may not have been installed correctly? Do we just contact the company that did the install to find out? The system has been approved by the city in which this lot is located.

We have the paperwork and permit but are just concerned to purchase and build on this lot as we are unfamiliar with this type system and if it has truly been installed into the rocky ground correctly. Every image I have found online shows these tanks and their caps sitting straight up, with no tilt or leaning.

On 2019-04-19 - by (mod) - tight space for getting septic installed

Meredith

You need an on-site septic engineer who can look at
- available space
- soil perc
- local septic regulations
- encumbrances such as nearby waterways

and propose an appropriate system

Just bringing in the tank may be easier using a fiberglass tank but you need space for effluent disposal - a drainfield

or if there is literally not enough space, your local health department might approve a packaged wastewater treatment system that can discharge sanitary effluent.

On 2019-04-18 by Meredith McIntosh

I have a tight space for getting septic in. steep in back and not much room on other sides of lot.
IMAGE LOST by older version of Clark Van Oyen’s useful Comments code - now fixed. Please re-post the image if you can. Sorry. Mod.


...

Continue reading  at AEROBIC SEPTIC SYSTEMS, ATUs or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see ALTERNATIVE SEPTIC DESIGN FAQs - questions & answers posted originally at this article

Or see these

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Suggested citation for this web page

SEPTIC SYSTEM DESIGN ALTERNATIVES - home at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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