5.5 Water Services, Private Water Mains, Disinfection & Storage Tanks
Key Takeaways
Private water mains and water services must be at least 5 feet horizontally from a sanitary sewer unless an exception is met, and never within 6 inches of a storm sewer.
Where water piping crosses a sanitary sewer, the water pipe within 5 feet of the crossing must be 12 inches above or 18 inches below the sewer, or sleeved.
New water supply systems must be flushed at each outlet for at least 1 minute, starting nearest the building control valve, until clear with no disinfectant.
New private water mains are disinfected per AWWA C651 or at 50 ppm chlorine for 24 hours or 200 ppm for 3 hours; combination fire and domestic services follow NFPA 24.
Ion-exchange softeners that discharge brine must regenerate on demand by meter or sensor, unless downstream treatment documents chloride reduction.
Definitions and sizes
- Water service: the part of the water supply system from the water main or private water supply up to and including the building control valve (SPS 381.01 (282)).
- Private water main: a water main serving 2 or more buildings that is not part of the municipal system (SPS 381.01 (195)).
- Both must be at least 3/4 inch and sized to deliver the required flow pressures (SPS 382.40 (7) (b)).
- Licensing: utility contractors and pipelayers install water services and private water mains from the street main to the immediate inside of the foundation wall (SPS 305.90 (1) (b) 4.).
Frost protection and routing (SPS 382.40 (8) (a) to (c))
- Install water services and private mains below the predicted frost depth (Figure 382.30-1 and Table 382.30-6), unless other freeze protection is provided.
- A hose bibb or hydrant through an exterior wall of a heated structure must be frost-proof and self-draining.
- Exterior water piping may not run in, under or above sanitary manholes or POWTS components.
- A private main or water service may not pass under one building to serve another, except for farm buildings on one property or buildings on the same property with a recorded piping document (within 90 days).
Separation from sewers (SPS 382.40 (8) (b))
| Situation | Requirement |
|---|---|
| General horizontal separation from a sanitary sewer | At least 5 feet |
| Crossing a sanitary sewer (water pipe within 5 ft of the crossing) | 12 in. above the sewer, 18 in. below it, or one pipe in a waterproof sleeve of building-sewer material |
| Closer than 5 ft to a pressurized sanitary sewer | Water pipe bottom at least 18 in. above the sewer and at least 3 ft horizontally |
| Closer than 5 ft to a non-pressurized sanitary sewer | Water pipe 12 in. above the sewer, or sewer of Table 384.30-2 materials, or a service of 2 in. or less more than 24 in. from the sewer |
| Within 5 ft of where the service enters the building | May be less than 12 in. above and within 24 in. of the sewer |
| Storm sewer | Never within 6 inches |
Separation from wells follows NR 811 and NR 812; separation from POWTS components follows Table 383.43-1. Underground water storage tanks must be at least 8 feet from a vessel holding a higher-hazard substance.
Worked example. A 1-inch copper water service and a 4-inch PVC sanitary sewer share a trench out to the street. The service must be 5 feet away horizontally unless an exception applies. One exception fits here: the service is 2 inches or less, so it may be closer than 5 feet if it stays more than 24 inches from the sewer. Laying the service on a shelf with its bottom at least 12 inches above the sewer is another option.
Testing
Water services and private water mains must be inspected before being covered and tested watertight at not less than the working pressure with water from a potable source (SPS 382.21 (2) (e)). A code note warns that NFPA 24 may impose more stringent tests on combination services and private mains that also supply fire protection.
NFPA 24 and combination services
NFPA 24 (2019), Installation of Private Fire Service Mains and Their Appurtenances, is incorporated by reference in Table 381.20 and is one of the references DSPS allows in the exam room. The plumbing code points to it in three places:
- Testing combination water services and private mains may be more stringent under NFPA 24 (SPS 382.21 (2) (e) note).
- Flushing and disinfection of new or repaired combination services and private mains must follow NFPA 24 (SPS 382.40 (8) (i) 4.).
- Materials for combination water services and combination private water mains must comply with NFPA 24 and SPS 384.30 (4) (d).
Private mains must also be designed for periodic flushing at a minimum of 3 ft/s per AWWA C651. Water service and private main polyethylene meeting ASTM D3035 may be installed by directional drilling per ASTM F1962.
Flushing and disinfection (SPS 382.40 (8) (i))
| System | Procedure |
|---|---|
| New water supply system | Flush and disinfect before use; flush each outlet, starting closest to the building control valve, for at least 1 minute and until clear with no trace of disinfectant |
| Altered or repaired portion | Flush at least 1 minute and until clear |
| New private water main or extension | AWWA C651, or flush clean, fill with 50 ppm chlorine for 24 hours or 200 ppm for 3 hours, then flush; repeat if bacteriological tests show contamination |
| Combination fire and domestic service or main | Flush and disinfect per NFPA 24 |
The department may require a water quality analysis. Samples may not be taken sooner than 24 hours after disinfection.
Water softeners (SPS 382.40 (8) (j))
Ion-exchange softeners that discharge brine during regeneration must be demand-initiated, using a water meter or sensor, unless a downstream treatment system documents chloride reduction. Timer-only softeners don't comply.
Water tanks for public potable use (SPS 382.40 (8) (jm))
- Pneumatic pressure tanks need a pressure relief valve, isolation and drain valves, and a label (manufacturer, model, volume, year and allowable pressure). Sizing may use a 5-minute peak flow.
- Storage tanks:
- Watertight and secured with locks.
- Overflow opening downward 6 to 12 inches above a splash pad, with a 4-mesh screen.
- Vents of at least 2 inches, ending 24 to 36 inches above grade with a 24-mesh stainless screen.
- Buried tank manholes at least 24 inches above grade.
- Drains to grade through an air gap, plus a bypass for maintenance.
- Not in a floodplain; the roof of an exterior tank at least 2 feet above grade.
- Influent ending at least 6 inches above high water.
- Potable water may not be stored next to nonpotable water separated by only a single wall.
A water service crosses a sanitary sewer. Which installation of the water piping within 5 feet of the crossing complies with SPS 382.40 (8) (b) 2.?
6 inches above the top of the sewer
18 inches below the bottom of the sewer
12 inches below the bottom of the sewer
Resting directly on the sewer pipe
Which disinfection procedure is permitted for a new private water main as an alternative to AWWA C651?
10 ppm chlorine for 1 hour
25 ppm chlorine for 12 hours
100 ppm chlorine for 30 minutes
50 ppm chlorine for 24 hours, or 200 ppm for 3 hours
How must a new or repaired combination water service that also supplies fire protection be flushed and disinfected?
In accordance with NFPA 24
In accordance with NFPA 13D
No disinfection is required for fire service piping
With 10 ppm chlorine for 2 hours
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