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| Applicability |
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| The Washington
State Department of Health document "Water Conserving On-Site
Wastewater Treatment Systems", effective 15 May 2000, is a helpful
guide with recommended application and design standards. |
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| Some pertinent performance,
application, and design standards are: |
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| Greywater treatment & disposal / reuse
systems must provide treatment and disposal at least equal to
that provided by conventional on-site systems. |
| All permitting, installation and inspection
requirements are the same as required in Chapter 246-272 WAC. |
| Greywater on-site sewage systems must provide
permanent, year-round treatment and disposal of greywater unless
this is already provided by an approved on-site system or connection
to public sewer. |
| Greywater systems are intended to treat and
dispose "residential strength" greywater. Greywater
exceeding typical residential strength must receive pre-treatment
to at least residential strength levels. |
| Greywater may be used for subsurface irrigation
of trees (including fruit trees), shrubs, flowers, lawns and
other ground covers but must not be used for watering of food
crops or vegetable gardens, any type of surface or spray irrigation,
to flush toilets/urinals or to wash walls, sidewalks or driveways. |
| Systems that use laundry wastewater only
are treated as a special case and may be permitted as such by
local health officers. Generally, such systems can be simpler
and smaller than other greywater systems. |
| Designers should consider plant water and
nutrient needs and limits, salt tolerances, depth of root zones,
etc. In general, shade-loving and acid loving plants do not
like greywater. Plants that are not suitable include rhododendrons,
hydrangeas, azaleas, ferns, magnolias and dogwood. Plants that
likely would do well with greywater irrigation include rosemary,
roses, oaks, cottonwood and bearded iris. |
| Most hand soaps and shampoos will not damage
plants at low residential concentrations. With detergents, conductivity,
alkalinity, sodium, boron and phosphate levels must be considered
to determine suitability. |
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