Graywater Root Zone Systems

Types of Graywater Systems

Plants love graywater! The hair, lint, food particles, kitchen oils, soaps, and detergents, found in graywater are all fertilizers for plants, and are readily absorbed by plant roots. In systems with no plant absorption (no root zone), such as conventional septic systems, these same fertilizers are wasted and can become groundwater pollutants.

All NutriCycle Graywater Systems are “root zone systems” that deliver graywater to a root zone in a variety of situations to complement the site. Types of graywater systems include:

Graywater Flowerbed

The root zone of ornamental perennials and annuals benefit from graywater.

Lewis Mill, Jefferson, Md

Graywater Lawn System

The existing lawn or new grass planting provides the root zone. The inspection ports for the irrigation chambers are flush with the grade for easy mowing.

Miller’s House, Jefferson, Md

Graywater Woodland System

Graywater irrigation chambers are installed in the root zone of existing trees and brush. The irrigation chamber inspection ports are above grade for easy access.

Dunn-Alexander Residence, Thurmont, Md

Graywater Greenhouse

Annuals and edible crops are fertilized and irrigated.

McLaughlin Residence, Wye Mills, Md

Graywater Wildflower Meadow

Similar to the Woodland System, but managed for landscape enhancement and to attract wildlife.

Bar-T Mountainside Camp, Urbana, Md

Graywater Dosing Basins

(Flooding Dose to Irrigation Troughs or Chambers)

In a NutriCycle Graywater System, graywater is distributed by flooding dose to irrigation chambers or troughs. The flooding dose carries graywater solids (hair, lint, food particles) out to the graywater to soil interface where they are absorbed by the root zone. With the flooding dose, perforated pipes, filters, septic tanks, pump-outs, and residual removal, are completely eliminated.

Graywater accumulates in a basin installed in the basement or outside in the ground with at-grade access. Basins are sized to generate the correct volume of dose determined by the square footage of chamber or trough that is to be flooded. Each time the dose volume is achieved, the dose is automatically sent to the chambers or troughs.

There are two basic types of graywater dosing basin:

The Pump Basin consists of the basin, a pump or pumps inside, and a controller mounted on the wall. Float switches inside tell the pump(s) when to go on and off to deliver the dose. When two pumps are used, two areas can be dosed in sequence, keeping the dose volume low.

The Dosing Siphon is completely non-electric. As graywater rises in the basin, air is trapped under the bell of the siphon. As graywater continues to rise, pressure increases on the trapped air until it suddenly evacuates (called “tripping”) out through the discharge pipe with the graywater dose following. When two siphons (as shown) are used, they will automatically alternate to deliver the dose to two areas in sequence.

Irrigation Chamber and Trough

Irrigation chambers and troughs provide an area for the graywater to flow into that is unobstructed yet contained, and the open bottom provides the area needed for soil root zone absorption. Chambers and troughs must be installed level so that the flooding dose will spread evenly to the ends, and so that the graywater can stand still while percolating, about 10 minutes.

Irrigation Trough

Checking level! Preparing to install irrigation chambers in a woodland graywater system.

Operation, Monitoring, and Cleaners

NutriCycle Graywater Root Zone Systems

(Flooding Dose to Irrigation Troughs or Chambers)


  • The equipment in this system is fully automatic and requires NO routine maintenance, including no pump-out and no residuals disposal.

  • Please read and save all information that comes with the equipment for future reference or troubleshooting.

  • All types of vegetation, including flowering annuals, grass, weeds, vegetables, shrubs, and small trees, are likely to thrive and perform adequately in absorbing nutrients and organic matter from the graywater.

  • Preferred vegetation includes:

    1. Evergreen perennials, in order to maintain an active root zone year round.

    2. Plants at least 2 or 3 feet high, in order to maintain a root zone size similar to the graywater-wetted area.

    3. Fast growing plants that love fertile, wet soils.

    4. Avoid acid loving plants – graywater is usually slightly basic.

    5. Avoid root crops that may be eaten raw.

  • Food scraps, hair, and grease go into the composter or elsewhere, not into the graywater system. Standard straining devices (cross-bars, strainer baskets, stopper systems) must be in use on all drains.

  • Garbage grinders are prohibited.


  • Check vegetation condition: add plants, pull weeds, thin, prune, harvest, mow, as needed for aesthetics, trough lid or inspection port access, and nutrient recycling. Vegetation that dies prematurely is either too sensitive or indicates too much sodium or toxins in the graywater.

  • Check graywater-to-soil interface (lift trough lid or open observation ports) for proper characteristics: color of wet soil; rough, perforated texture from soil biological activity; presence of hair, lint or food particles from recent dose; presence of decomposer organisms such as ants, sow bugs, earthworms and their castings, spiders, centipedes, etc.; presence of roots or root hairs; deposit on side walls indicating proper flooding dose depth of about 1 inch. If these characteristics are present, DO NOT DISTURB!
  • A thin, gray biomat may appear on the whole interface area during the cold season and is normal. If the biomat is over one-quarter inch thick or black, then the system will be prone to excessive ponding and should be checked for: toxins in flow, too high flow, malfunctioning dose operation, uneven dose distribution, mistakes in design or construction, the need for expansion, the need to add insulation or heat, lack of root zone activity, inadequate top soil characteristics.

  • Restoration of an obstructed or out-of-level interface in a trough system is achieved by removing the lid, adding or removing soil, and raking and tamping as needed. For chamber systems, the chamber must be dug out, the interface restored, then the chamber replaced.

  • The dose counter can be used to determine the actual flow: number of doses, times gallons per dose, divided by days lapsed, equals gallons per day.


  • Use Cleaners Sparingly: The human and environmental health hazards from using and misusing cleaners, sanitizers, and disinfectants often outweigh the health benefits from their use. The best practice is to use them as little as possible, and rely on the natural sanitizing properties of air as much as possible.

  • Use Biocompatible Cleaners: “Biocompatible” cleaners, cleaners that biodegrade into plant nutrients, are the best because they are readily absorbed by the root zone, which enhances root zone activity, and recycles clean water to the ground water. Bio Pac Dishwashing Liquid and Bio Pac Ultra Laundry Liquid are the only biocompatible cleaners currently available on the East Coast and are sold at most health food store. Bio Pac uses the name “Oasis” on the West Coast. The Bio Pac website has useful information (
  • Use Liquid Laundry Detergents (Avoid Sodium): Sodium is the most important compound to avoid. Sodium is toxic to microbial activity, destroys soil structure, prevents percolation, and causes clogging. Sodium is most prevalent in powdered laundry detergents, so a simple switch to liquid laundry detergents solves the problem. Also, water softeners add sodium to the water and should be avoided or used minimally.

  • Commercial cleaners, sanitizers, and disinfectants are probably O.K. for graywater systems, as long as they are used in moderation and in strict accordance with the instructions on the container. Proper dilution and application insures that the chemicals are “reacted” (rendered inactive) prior to arriving in the graywater system so that their negative effect on the soil microbes in minimized. Cleaners biodegrade more completely in a shallow graywater system than in a septic system, so cleaner water is recycled to the ground water.

Graywater Flows Compared

Sewage Design

Graywater Design
Flow Allowed

(% reduction)

Graywater Design
Flow Proposed

(% reduction)

Actual Flow from
Dose Counters

(% reduction)

Hanson Residence 75 37.5 (50%) 37.5 (50%)

19 (75%)

Hamblin Residence

75 48 (36%) 37.5 (50%) 25 (66%)
Schoonover 75 37.5 (50%) 37.5 (50%)

24 (68%)


75 37.5 (50%) 37.5 (50%) 24 (68%)
Naylor 75 37.5 (50%) 37.5 (50%)

11 (85%)

Williams 75 37.5 (50%) 37.5 (50%)

12 (84%)

Rippeon 75 37.5 (50%) 37.5 (50%) 5 (93%)


White Plains Post Office 250 12 (95%) 12 (95%)

8 (97%)

Picturesque Landscaping

150 10 (93%) 10 (93%)

0.2 (99%)

Frederick Golf Club

3,000 1,000 (33%) 50 (98%)

5.6 (99%)

Lake Shore Athletic Complex

1,500 180 (88%) 66 (96%) 7.6 (99%)

Sugarloaf Citizens

Assn Offices

450 283.5(37%) 100(78%) 1.6(99%)

Bar-T Camp

5250 2625 (50%) 770 (61%) 186 (93%)

These actual flows support design flow reductions of 50% for residential graywater systems, and up to 98% for commercial graywater systems, from standard sewage design flows.

Design Criteria Compared1

NutriCycle Graywater Root Zone Systems 2,3


Soil Absorption Area 75% reduced5 Full size
Treatment Zone 2 feet 4 feet
Septic Tank Prohibited6 Required
Shallow Irrigation Chamber or Trough7 Allowed Prohibited
Distance to Well 25 feet 100 feet

Distance to drainage ways, steep slopes,

rock outcrops

6 feet 25 feet
Topsoil fill Allowed Prohibited
Recovery Areas 75% reduced Full sized
Set-aside area (future) 2,500 sq ft 10,000 sq ft
Minimum Ownership (future) 20,000 sq ft 40,000 sq ft
  1. These criteria are based on field experience with 15 systems.
  2. NutriCycle Graywater Root Zone Systems are part of the NutriCycle System, which includes composting toilets, and a permitted plan for landscape use of the compost and liquid fertilizer.
  3. Disclosure that “only” NSF approved composting toilets, low flow fixtures, and no garbage grinder, can be used on this property”, may be appropriate.
  4. Rationale for these Criteria are available from NutriCycle Systems.
  5. Minimum area requirements (residential) and minimum set-back distances are generally 75% reduced from the sewage requirements. This reflects both the hydraulic load reduction of 50 % (no flush toilet, low-flow fixtures, no garbage grinder), and an additional 50% reduction for low pollutant load (no human body products, no garbage).
  6. Septic conditions are negative to the aerobic design of graywater root zone systems.

NutriCycle Graywater Systems receive only domestic wash water, called “graywater”, and use it to irrigate and fertilize vegetation in the landscape by way of irrigation chambers or troughs.