R317-401-5. Design of Graywater Systems

5.1. The basis of design for a graywater system shall be: (a) according to Table 1 or Table 2 for residential usage; TABLE 1 Design Flow, Entire Single Family Dwelling Number of Bedrooms Flow, gallons per day Two Bedrooms (Minimum) 160 Three Bedrooms 240 Each Additional Bedroom 40 TABLE 2 Design Flow, Single Fixture Fixture Flow, gallons per day/bedroom Washing Machine 30 Shower/Bath Tub 50 Hand Wash Basin 5 Other Sources Shall be sized by a qualified designer TABLE 3 Separation Distances Minimum Horizontal Distance From (ft) Surge Tank Subsurface Discharge Building or Structures (a) 5 (b) 2 Property Line 5 5 Public Drinking Water Sources (c) (d) (d) Non-public Drinking Water Sources Protected (grouted) Source 50 100 Unprotected (ungrouted) Source 50 (e) 200 (e) Streams, Ditches, and Lakes (c) 25 100 (f) Seepage Pits 5 10 Absorption System and Replacement Area 5 10 Septic Tank 5 5 Culinary Water Supply Line 10 10 (g) Notes: (a) Including porches and steps, whether covered or uncovered, but does not include carports, covered walks, driveways and similar structures. (b) For above ground tanks the regulatory authority may allow less than five feet separation. (c) As defined in Rules R309-600 and R309-605. (d) Recommended separation distances will comply with the Source Water Protection requirements listed in Rules R309-600 and R309-605. (e) Recommended separation distance may increase at the discretion of the regulatory authority for the purpose of protecting public health. (f) Lining or enclosing watercourse or location above graywater discharge area may justify reduced separation distance(s) at the discretion of the regulatory authority. (g) As defined in Rule R309-550. 5.2. Surge Tank (a) a surge tank is required for a Tier 2 graywater system. Plans for a surge tank shall include dimensions, structural, bracing and connection details, and a certification of structural suitability for the intended installation from the manufacturer. (b) a surge tank shall be: (i) a minimum of 250 gallons in volumetric capacity to provide settling of solids, accumulation of sludge and scum unless justified with a mass balance of inflow and outflow and type of distribution for graywater discharge; (ii) accessible to the surface with a locking, gasketed access opening, or approved equivalent, to allow for inspection and cleaning; (iii) constructed of structurally durable materials to withstand all expected physical forces, and not subject to excessive corrosion or decay; (iv) watertight; (v) anchored against overturning; (vi) installed below ground on dry, level, well-compacted soil or above ground on a level, four-inch thick concrete slab; (vii) permanently marked showing the rated capacity, and the words GRAYWATER IRRIGATION SYSTEM, DANGER - UNSAFE WATER on the unit; (viii) provided with an overflow pipe: (A) of diameter at least equal to that of the inlet pipe diameter; (B) connected permanently to the building sewer; (C) equipped with a check valve or backwater valve, accessible for cleaning and maintenance, to prevent backflow from building sewer; and (D) which may not include a shut-off valve. (ix) provided with a drain pipe of diameter at least equal to that of the inlet pipe diameter; and (x) provided with a vent pipe in conformance with the requirements of the International Plumbing Code and local building code; 5.3. Valves and Piping. (a) Graywater piping that discharges into a surge tank or has a direct connection to any sanitary drain or sewer piping shall be downstream of an approved water seal type trap. If no such trap exists, an approved vented running trap shall be installed upstream of the connection to protect the building from any possible waste or sewer gases. (b) Vents, venting, and piping shall meet the requirements of the International Plumbing Code and local building code. (c) All graywater piping shall be purple or shall have a continuous marking with the words DANGER - UNSAFE WATER. (d) A graywater system shall have a 3-way diverter valve at any stub--out connection. A 3-way diverter valve shall be connected to a fixture or inlet, an approved graywater system, and building sewer. (e) Any 3-way diverter valve shall be readily accessible and clearly marked to indicate directional flow to graywater system or building sewer.