Current through Register Vol. 24-18, September 15, 2024
(1) Tier 2 and
Tier 3 greywater irrigation systems must be designed by a qualified
professional, except:
(a) The local health
officer may allow a resident owner of a single-family residence, not adjacent
to a marine shoreline, to design a system for his or her residence when the
system reuses no more than three hundred gallons per day of greywater;
or
(b) The local health officer may
design the system if he or she performs the soil and site evaluation.
(2) The person designing a Tier 2
or Tier 3 system must use the following criteria when developing the design:
(a) Storage and pump tanks must be:
(i) Constructed of solid, durable materials
not subject to excessive corrosion or decay;
(ii) Water-tight;
(iii) Tamper proof and not susceptible to
intrusion by humans or vectors;
(iv) Installed below ground on dry, level,
well compacted soil or above ground on level, stable footing;
(v) Anchored to prevent
overturning;
(vi) Provided with an
overflow pipe with a diameter at least equal to that of the inlet pipe diameter
that flows by gravity to the approved public sewer system or on-site sewage
system with a check valve or backwater valve, as appropriate, that prevents
backflow from sewer or septic tank; and
(vii) Provided with a drain pipe and a vent
pipe.
(b) The operating
capacity must be based on the estimated flows of greywater diverted from the
approved public sewer or on-site sewage system.
(i) The total flow available may be estimated
using the flow from each fixture multiplied by the number of people using the
fixtures. The flow from each fixture is based on design flow of the
fixture.
(ii) If the fixture's
design flow is unknown, the following standards must be used:
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Laundry:
|
Water conserving washing machine - 8 gallons per
person per day
|
|
Traditional washing machine - 11 gallons per person
per day
|
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Laundry sink - 3 gallons per person per day
|
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Bathroom:
|
Water conserving sink - 5.4 gallons per person per
day
|
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Water conserving shower - 10 gallons per person per
day
|
|
Traditional sink - 6 gallons per person per
day
|
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Traditional shower - 17 gallons per person per
day
|
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Bathtub:
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24 gallons per bath
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Kitchen sink:
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6 gallons per person per day
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Dishwasher:
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1 gallon per person per day
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(c) If the building is served by an on-site
sewage system with design flows of less than three thousand five hundred
gallons per day, the total flow of greywater diverted must not adversely affect
the functioning of the on-site sewage system.
(d) The sensitivity of the site where the
greywater irrigation system will be installed must be considered.
(i) Examples of sensitive sites include
shellfish growing areas, designated swimming areas, designated wellhead
protection areas for Group A public water systems, areas in which aquifers used
for potable water as designated under the Growth Management Act, chapter 36.70A
RCW, are critically impacted by recharge, and other areas identified by the
local management plan required in WAC
246-272A-0015, where fecal
coliform constituents or other greywater constituents can result in public
health or water quality concerns.
(ii) When the greywater irrigation system
will be installed in an area that is not covered by a local management plan
required in WAC
246-272A-0015, examples of
sensitive sites include similar types of areas where greywater constituents can
result in public health or water quality concerns.
(e) For greywater irrigation systems
conveying greywater from a nonresidential source, documentation must be
provided that:
(i) Shows the greywater
consists only of domestic type flows and does not include any other type flows;
and
(ii) Identifies how chemicals
and other hazardous materials will be kept out of the greywater.
(3) The person
designing the system shall ensure that the owner is provided with the record
information required under WAC
246-274-200(1)(i)
and 246-274-300(3)(h).
Statutory Authority: RCW 90.46.015. 11-02-011, §
246-274-410, filed 12/28/10, effective
7/31/11.
