11.3 Water Reuse, Plumbing Treatment Standards & Stormwater Infiltration
Key Takeaways
Table 382.70-1 requires NR 811 and 812 approved sources for drinking, cooking, food, medical and personal hygiene uses; reused water serves only listed nonpotable uses that meet their limits.
Water closet and urinal wastewater may not be reused for drinking water, except through DNR-permitted treatment works or a POWTS with in situ soil (SPS 382.34 (3) (a)).
Nonpotable water treatment devices are listed under NSF/ANSI 350 or 350-1 and need an onsite maintenance log (filters at intervals under 3 months; pumps, valves, tanks and backflow devices at start-up and at least every 12 months).
Stormwater infiltration systems need 5 feet of suitable soil to groundwater or bedrock (10 to 20% fines) or 3 feet (20% fines or more), 1 foot for roof runoff, and must drain within 72 hours.
Infiltration systems are set back 10 feet from buildings, 10 feet from POWTS tanks and storage tanks, 5 feet from POWTS dispersal components and property lines, and 15 feet from in-ground pools.
The reuse framework
SPS 382.34 (3) (a) allows graywater, stormwater, clear water, blackwater and other approved wastewater to be reused under SPS 382.70. One firm limit applies: wastewater from water closets and urinals may not be reused for drinking water, except through DNR-permitted treatment works or a POWTS with an in situ soil component. SPS 382.70 (3) requires every plumbing system to supply water suitable for its intended use that protects public health and the waters of the state.
Table 382.70-1: plumbing treatment standards (selected)
| Intended use | Standard at the outlet |
|---|---|
| Drinking, cooking, food processing, pharmaceutical and medical uses | NR 811 and 812 approved sources |
| Personal hygiene, bathing, showering | NR 811 and 812 approved sources |
| Automatic fire protection | As acceptable to the local authority |
| Swimming pool makeup water | NR 811 and 812 approved sources |
| Cooling water | pH 6 to 9; BOD5 under 50 mg/L; TSS under 30 mg/L; free chlorine 1.0 to 10.0 mg/L |
| Subsurface infiltration and irrigation using reuse water | Oil and grease under 15; BOD5 under 30; TSS under 35 mg/L; fecal coliform under 200 cfu/100 mL; 12 in. of medium sand or finer above groundwater or bedrock |
| Subsurface irrigation using stormwater | Oil and grease under 15; TSS under 60 mg/L |
| Surface or spray irrigation using stormwater and clearwater | BOD5 under 10; TSS under 5 mg/L |
| Surface irrigation (not food crops), vehicle and clothes washing, air conditioning, dust control, concrete | pH 6 to 9; BOD5 under 10; TSS under 5 mg/L; free chlorine 1.0 to 10.0 mg/L |
| Toilet and urinal flushing | pH 6 to 9; TSS 5 mg/L or less; free chlorine 0.1 to 4.0 mg/L (see the table for BOD) |
| Uses not listed | Contact the department |
Chlorine and pH limits apply only to reuse treatment devices. Stormwater standards are annual averages. Industrial and WPDES-permitted discharges are excluded.
Treatment devices and systems (SPS 382.70 (5))
Devices that treat nonpotable water for these uses must be listed under NSF/ANSI 350 or 350-1 (or approved under SPS 384.50), designed per SPS 382.34 (3) (a), and provided with three things.
1. A maintenance log kept onsite by the owner:
| Action | Interval |
|---|---|
| Inspect, clean and replace filters | Less than 3 months |
| Verify treatment components meet standards | Per manufacturer and department |
| Pump, valve and pressure tank operation | At start-up and at least every 12 months |
| Clean storage tanks; check locks | At start-up and at least every 12 months |
| Labeling and markings | At start-up and at least every 12 months |
| Mulch basins | As needed to prevent ponding and runoff |
| Cross connection control inspection and test | At start-up and at least every 12 months |
2. An onsite manual with a system diagram, operation and maintenance instructions, shutdown steps, manufacturer contacts, model number and sources for expendable parts.
3. Indelible labeling per NSF 350, visible after installation.
Connecting reuse to the building
- Reuse piping and outlets are labeled with purple tags or bands (Table 382.40-1a) at no more than 25-foot intervals. Nonpotable hose bibbs are labeled and have removable handles.
- The potable makeup to a reuse system is protected per SPS 382.41. Nonpotable water may feed a treatment device designed to meet Table 382.70-1 (SPS 382.40 (3) (a) 2.).
- Water supply piping may be reused only for an equal or higher degree of hazard (SPS 382.22 (4) (b)).
- Plan review: onsite residential and commercial water reuse treatment systems (Table 382.20-1 line 7), and stormwater and clearwater detention, treatment and infiltration systems serving public buildings (line 6), go to the department. Agent municipalities may review them if the department authorizes.
- Underground stormwater reuse tanks are at least 8 feet from sanitary sewers (SPS 382.36 (7) (d) 9.).
Stormwater and clearwater subsurface infiltration (SPS 382.365)
| Topic | Requirement |
|---|---|
| Site and soil evaluation | Per SPS 385.40 (3) (a) and 385.30 (1) (c), by a registered soil tester under SPS 305.33 or a licensed soil scientist; also DNR technical standards 1002 and 1004 |
| Influent | Table 382.70-1 subsurface infiltration standards |
| In situ soil separation to groundwater or bedrock | 5 feet of suitable soil with 10 to 20% fines; 3 feet with 20% fines or more; measured to mounded groundwater where mounding applies |
| Roof runoff or equivalently treated water | At least 1 foot of material finer than coarse sand |
| Engineered soil (bioretention) | At least 24 inches (18 inches with documentation and approval), above any limiting factor |
| Groundwater mounding analysis | Required when the system is wider than 15 feet |
| Drain-down | Within 72 hours; surface ponding within 24 hours |
| Orientation | Long dimension along the contour; level infiltrative surface below original grade (irrigation excepted) |
| Installation weather | Not on frozen soil; remove snow; stop if the soil rolls into a 1/4-inch wire |
Setbacks (Table 382.365-4):
| Feature | Setback |
|---|---|
| Building | 10 ft |
| Holding tank or stormwater collection tank | 10 ft |
| POWTS dispersal component | 5 ft |
| POWTS holding or treatment component | 10 ft |
| Property line | 5 ft |
| In-ground swimming pool | 15 ft |
| Wells | NR 811 and 812 |
No substance may be discharged into an infiltration system that causes NR 140 groundwater limits to be exceeded at a point of standards application. Deleterious substances must be treated under SPS 382.34 first.
Worked example
A commercial building wants to flush its toilets with harvested roof water.
- The system is an onsite water reuse treatment system, so plans go to DSPS (Table 382.20-1 line 7).
- The treatment device must be NSF/ANSI 350 listed and deliver pH 6 to 9, TSS of 5 mg/L or less and free chlorine of 0.1 to 4.0 mg/L at the water closets.
- The flushing piping is purple-labeled.
- The potable makeup to the storage tank uses an air gap or other Table 382.41-1 protection.
- The owner keeps the onsite log: filters checked at least every 3 months, and pumps, valves, tank and backflow device annually.
Which use does Table 382.70-1 restrict to NR 811 and 812 approved water sources?
Toilet and urinal flushing
Surface irrigation of lawns
Personal hygiene, bathing and showering
Cooling water
Under what standard must a nonpotable water treatment device for reuse be listed under SPS 382.70 (5)?
NSF/ANSI 61 and NSF/ANSI 372
NSF/ANSI 350 or 350-1
NSF/ANSI 44 softener standard
ASSE 1013 and CSA B64.4
What minimum depth of suitable in situ soil separation does SPS 382.365 require for a stormwater infiltration system in soil with 20 percent or more fines?
5 feet
1 foot
2 feet
3 feet
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