6.5 Nonpotable Water Systems: Identification, Separation & Storage Tanks
Key Takeaways
IPC 608.9.2.1 requires purple pipe identification for reclaimed, rain and graywater distribution systems, consistent throughout the building.
IPC 608.9.2 requires nonpotable pipe identification at intervals of not more than 25 feet and at every wall, floor or roof penetration.
IPC 1301.2.2 requires nonpotable water used for water closet and urinal flushing to pass through a 100-micron or finer filter.
IPC 1301.11 requires 5 feet of undisturbed or compacted earth between nonpotable piping and both the building sewer and potable water piping.
IPC 1301.9.10 requires nonpotable storage tanks to stay watertight for 24 hours when filled to the overflow line.
Nonpotable Water Systems: Identification, Separation & Storage Tanks
Rainwater harvesting and graywater reuse reduce demand on public water, but they put two water systems in one building. The main risk is a cross connection, where someone accidentally ties a nonpotable pipe to a drinking water line. The ICC P3 outline weights nonpotable water at 5 percent within the Water Supply domain. IPC Chapter 13 governs these systems, and IPC 608.9 governs pipe identification.
Scope and Water Quality (IPC 1301.1 and 1301.2)
- Scope (1301.1): Chapter 13 governs the materials, design, construction and installation of systems that collect, store, treat and distribute nonpotable water. For nonpotable rainwater systems, CSA B805/ICC 805 is an approved alternative. The use of nonpotable water must also comply with local laws and rules.
- Water quality (1301.2): Each end use must meet the water quality set by the jurisdiction. Where water from different sources is combined, the system meets the most stringent applicable requirement.
- Residual disinfectant (1301.2.1): Where chlorine is used, the water may contain not more than 4 ppm of chloramines or free chlorine (tested per ASTM D1253). Ozone may not leave gas bubbles with elevated ozone at the point of use.
- Filtration (1301.2.2): Water used for water closet and urinal flushing passes through a 100-micron (0.1 mm) or finer filter.
- Reclaimed water exception: Reclaimed water from a wastewater treatment facility is exempt from both the disinfectant limit and the filtration rule.
- Permits (1301.4): Construction documents, engineering calculations and diagrams for the nonpotable system are submitted with the permit application.
Identification: Signs and Purple Pipe (IPC 1301.3 and 608.9)
Outlet Signage (1301.3 and 608.9.1)
Every nonpotable outlet, such as a hose connection, open-ended pipe or faucet, is labeled at the point of use:
"Nonpotable water is utilized for [application name]. CAUTION: NONPOTABLE WATER – DO NOT DRINK."
Letters are at least 0.5 inch high in a contrasting color, on corrosion-resistant waterproof material or printed on the fixture, with the "Do Not Drink" pictograph.
Distribution Pipe Marking (608.9.2)
- Color: Nonpotable distribution piping is purple. Purple identifies reclaimed, rain and graywater systems, and the color must be consistent throughout the building (608.9.2.1).
- Marking: The pipe is embossed or stamped "CAUTION: NONPOTABLE WATER – DO NOT DRINK", or wrapped with purple identification tape.
- Content and flow: Identification states the contents and has an arrow showing flow direction. Hazardous systems also state the nature of the hazard.
- Spacing: Identification repeats at intervals of not more than 25 feet and at each wall, floor or roof penetration.
- Tape (608.9.2.3): Identification tape is at least 3 inches wide, with white or black lettering on a purple field. On rainwater distribution pipe it runs on top of the pipe for its whole length, fastened at least every 10 feet.
| Pipe Diameter (inches) | Color Field Length (inches) | Letter Size (inches) |
|---|---|---|
| 3/4 to 1-1/4 | 8 | 0.5 |
| 1-1/2 to 2 | 8 | 0.75 |
| 2-1/2 to 6 | 12 | 1.25 |
| 8 to 10 | 24 | 2.5 |
| Over 10 | 32 | 3.5 |
Source: IPC Table 608.9.2.2. Collection piping that carries untreated graywater or rainwater to the tank needs no extra marking beyond normal DWV marking (1302.4.4 and 1303.7.4).
Protecting the Potable System (IPC 1301.5, 1301.9.4 and 1301.12)
- Potable connections (1301.5): Where a potable system connects to a nonpotable system, the potable supply is protected against backflow per Section 608.
- Makeup water (1301.9.4): Where the use needs an uninterrupted supply, potable or reclaimed water provides makeup water, with backflow protection and a full-open valve on the makeup line. Automatic fill valves keep the level above the source inlet and any pump intake.
- Outdoor outlets (1301.12): Outdoor hose bibbs, wall hydrants and yard hydrants on nonpotable water are in a locked vault or operate only with a removable key.
Trench Separation (IPC 1301.11)
Nonpotable collection and distribution piping and reclaimed water piping are separated from the building sewer and potable water piping underground by 5 feet of undisturbed or compacted earth. Nonpotable piping may not run in, under or above cesspools, septic tanks, drain fields or seepage pits. The exceptions allow:
- Nonpotable pipe 12 inches above the top of the sewer within the 5-foot zone, using Table 702.3 materials.
- A potable service pipe 12 inches above the top of the nonpotable pipe, using Table 605.4 materials.
- Nonpotable pipe in the same trench as a building sewer of Table 702.2 materials.
- Crossings sleeved 5 feet each side of the centerline, using Table 702.2 materials.
- Outdoor irrigation piping downstream of the backflow preventer.
Storage Tanks (IPC 1301.9)
| Item | Requirement |
|---|---|
| Sunlight (1301.9.1) | Above-grade tanks are opaque and UV-resistant, shaded, or installed in a garage, crawl space or shed |
| Materials (1301.9.2) | Durable, nonabsorbent and corrosion-resistant; wood tanks without makeup water need a flexible liner |
| Flotation (1301.9.3.1) | Underground tanks in soil that can become saturated are ballasted so the combined weight equals or exceeds buoyancy |
| Overflow (1301.9.5) | Sized per Table 606.5.4, screened, no shutoff valve, with a cleanout |
| Access (1301.9.6) | Lockable opening; outdoor below-grade tanks need a 24-inch manhole extending 4 inches above grade, and service ports at least 8 inches in diameter |
| Venting (1301.9.7) | Sized per Chapter 9 on the aggregate influent pipe diameter; not connected to sanitary vents; cap or U-bend facing down |
| Draining (1301.9.8) | Pump or low-point drain sized per Table 606.5.7 |
| Signage (1301.9.9) | Rated capacity, "CAUTION: NONPOTABLE WATER – DO NOT DRINK", and "DANGER – CONFINED SPACE" at entry openings |
Tank test (1301.9.10): The tank is filled to the overflow line and must stay watertight for 24 hours with seams exposed. Water is then added for 15 minutes to prove the overflow drains. The tank drain and the makeup water's automatic shutoff are also checked.
Plan Reviewer Verification Checklist: Nonpotable General
- Permit Package: Calculations and diagrams are included, and the end-use water quality is identified (1301.2 and 1301.4).
- Flush Water Filtration: Systems that supply water closets and urinals have a 100-micron or finer filter (1301.2.2).
- Purple Pipe: Contents, flow arrows, marking at 25-foot intervals and at each penetration, and Table 608.9.2.2 sizes are specified (608.9).
- Outlet Signs: Signs and pictographs are at every outlet, and outdoor outlets are locked or key-operated (1301.3 and 1301.12).
- Separation: There is 5 feet of earth from the sewer and potable piping, or a listed exception applies (1301.11).
- Tanks: Overflow has no valve, vents are independent, access is secured, signs are shown, and the 24-hour test is specified (1301.9).
A rainwater harvesting system will supply water closets and urinals in an office building. Under IPC Section 1301.2.2, what filtration is required?
A 5-micron cartridge filter for all uses
A 500-micron screen at the downspout only
No filtration if the water is disinfected
A 100-micron or finer filter
Under IPC Section 608.9.2, how often must identification be repeated on nonpotable distribution piping?
At intervals of not more than 50 feet, and at each riser and fixture branch
At intervals of not more than 10 feet on all piping
Every 25 feet or less, and at each wall, floor or roof penetration
Only at the storage tank and at each fixture
A site plan shows a nonpotable rainwater distribution pipe 3 feet horizontally from the potable water service, in separate trenches at the same depth. What does IPC Section 1301.11 require?
It complies, because 3 feet of separation is enough for rainwater
It does not comply unless 5 feet of earth separates them or an exception applies
It complies, if the rainwater pipe is purple
It does not comply, because potable water piping may never cross nonpotable piping
During plan review, the plumbing designer shows a gate valve on a nonpotable storage tank's overflow pipe so the tank can be isolated for cleaning. What is the correct finding under IPC Section 1301.9.5?
Reject it, unless a check valve is also added downstream of the gate valve
Reject it; the overflow drain may not have a shutoff valve
Accept it, if the valve is a full-port ball valve
Accept it, if the valve is locked open
Sections you finish are checked off in the contents.