Types

• First-Flush Diverters and Debris Screens
  Screens, debris excluders, and first-flush diverters that keep leaves and the dirtiest runoff out of rainwater storage.
• Rainwater Catchment and Conveyance
  Roof catchment surfaces, gutters, and leaders used to collect rainwater for harvesting, with roof material choice and conveyance sizing.
• Rainwater Cisterns and Storage Tanks
  Above-ground and underground tanks that store harvested rainwater, with materials, sizing, siting, and the inlet, outlet, overflow, vent, and access details.
• Rainwater Filtration and Disinfection
  Filters and disinfection used to treat harvested rainwater to the quality its end use requires, from sediment filtration to UV and chlorination.
• Rainwater Harvesting and Water Conservation
  Collecting roof runoff in cisterns for irrigation and other nonpotable uses, with sizing by water budget and first-flush diversion.
• Rainwater Harvesting Systems
  Systems that collect roof runoff, store it in cisterns, and treat and distribute it for irrigation, toilet flushing, and other uses.
• Rainwater Pumps and Distribution
  Pumps, controls, make-up water, and distribution piping that deliver harvested rainwater to points of use without crossing into the potable supply.
• Roof Drainage Systems
  Roof drains, scuppers, gutters, leaders, and overflow systems, with tapered slope and crickets, used to remove rainwater from roofs and prevent ponding and overload.

Code reference

Always verify the adopted code edition and local amendments for the project jurisdiction.

Governing editions

General

• IPC 2024, Section 1303.1 and 1301.1: nonpotable rainwater collection, storage, treatment, and distribution as permitted by the jurisdiction; CSA B805/ICC 805 may be used as an alternative; fire protection water follows the IFC (rainwater harvesting systems)
• IPC 2024, Section 1301.4: permit required, with construction documents and calculations (rainwater harvesting systems)

Collection and conveyance

• IPC 2024, Section 1303.2: collection from above-ground impervious roofs of approved materials; vehicular parking and pedestrian surfaces only where approved (rainwater catchment and conveyance)
• IPC 2024, Sections 1303.5 to 1303.5.3: gutters, leaders, and collection piping watertight, sloped continuously to inlets at 1/8 in. per ft minimum with no pooling (siphonic systems per manufacturer), sized per Section 1106.6, with cleanouts to all filters, flushes, pipes, and downspouts (rainwater catchment and conveyance)
• IPC 2024, Sections 1303.3, 1303.4, 1303.6, and 1301.7: debris excluder at each downspout or leader; automatic first-flush diverter with maintenance access; roof washer and excluder discharge not to the sanitary sewer, not onto roofs, and self-draining between storms; insect and vermin protection on inlets and vents (first-flush diverters and debris screens)

Storage tanks

• IPC 2024, Sections 1301.9.1 to 1301.9.3: tanks opaque or shaded above grade; base supports the full tank weight; buried tanks in saturated soil ballasted or tied down to exceed buoyancy and resist earth and surface loads (rainwater cisterns and storage tanks)
• IPC 2024, Section 1301.9.2: tanks approved, durable, nonabsorbent, and corrosion resistant, compatible with upstream disinfection; wooden tanks without a make-up source need a flexible liner (rainwater cisterns and storage tanks)
• IPC 2024, Section 1303.10 and Table 1303.10.1: tank setbacks of 2 ft from the critical root zone of protected trees, 5 ft from adjoining private lot lines, 5 ft from seepage pits, and 5 ft from septic tanks; inlets with minimal turbulence; outlets at least 4 in. above the tank bottom (rainwater cisterns and storage tanks)
• IPC 2024, Sections 1301.9.5 to 1301.9.8: overflow sized per Table 606.5.4, protected from pests, discharged away from foundations and neighbors, with no shutoff valve; vent sized per Chapter 9, separate from sanitary vents, capped or turned down, and at least 4 in. above grade; at least one lockable access, with below-grade manholes at least 24 in. square or round and service ports at least 8 in. in diameter and 4 in. above grade (treated-water tanks under 800 gal below grade need only an 8 in. port); pump or drain at the low point with a cleanout (rainwater cisterns and storage tanks)
• IPC 2024, Section 1301.9.9: tank labeled with rated capacity and the nonpotable warning, with confined-space warning at openings allowing entry, letters at least 1/2 in. high (rainwater cisterns and storage tanks)
• IPC 2024, Section 1301.9.10: tank test by filling to the overflow and holding 24 hours, then 15 minutes of added water to verify overflow drainage, drain operation, and make-up shutoff (rainwater cisterns and storage tanks)
• IPC 2024, Section 1301.8: freeze protection of tanks and piping where sustained freezing occurs (rainwater cisterns and storage tanks)

Treatment

• IPC 2024, Sections 1303.8, 1303.9, 1301.2, 1301.2.1, and 1301.2.2: filtration to the end use with access, a pressure gauge, and shutoff valves up and downstream; disinfection as needed with residual chlorine tested to ASTM D1253; chloramines or free chlorine 4 ppm maximum; toilet and urinal flushing water through a 100 micron or finer filter; the most stringent requirement governs where sources mix (rainwater filtration and disinfection)
• IPC 2024, Section 1303.15.9: ASTM E2727 identifies site conditions that affect raw rainwater quality (rainwater filtration and disinfection)

Pumping, make-up water, and backflow

• IPC 2024, Sections 1303.12 and 1303.13: pumps, valves, and filters removable for service; flow and pressure per Section 604; pressure-reducing valve where static pressure exceeds 80 psi (rainwater pumps and distribution)
• IPC 2024, Section 1301.9.4: potable or reclaimed make-up water where uninterrupted supply is required, backflow protected per Section 608, a full-open valve on the make-up line, and an automatic fill valve that holds a minimum level above the source inlet and pump intake (rainwater pumps and distribution, backflow preventers)
• IPC 2024, Sections 1301.5, 1303.11.1, and 1303.15.6: backflow protection of potable connections per Section 608; backwater valves on each overflow and tank drain per Section 714; backflow devices tested per Section 312.11 (rainwater pumps and distribution, backflow preventers)

Identification, signage, and installation

• IPC 2024, Section 1303.14 and 1301.3: distribution piping per Sections 604 and 605 and marked per Section 608.9 (irrigation piping downstream of a backflow preventer exempt); signage "CAUTION: NONPOTABLE WATER - DO NOT DRINK" with the Figure 1301.3 pictograph at each nonpotable outlet, letters at least 1/2 in. high (rainwater pumps and distribution)
• IPC 2024, Sections 1301.11 and 1301.12: 5 ft of undisturbed or compacted earth between nonpotable piping and building sewers or potable piping, with exceptions; outdoor outlets in a locked vault or requiring a removable key (rainwater pumps and distribution)

Testing and maintenance

• IPC 2024, Sections 1303.7 and 1303.15.1 to 1303.15.8: collection and vent piping approved for drainage and venting; testing of gutters (1 gal poured at the far end), first-flush diverters, DWV piping per Section 312, tanks, make-up and distribution piping per Section 312.6, inlet and vent protection, and point-of-use water quality (rainwater harvesting systems)
• IPC 2024, Section 1303.16: hardcopy operation and maintenance manual with schematic, components list, maintenance schedule with consumable part numbers, and startup, shutdown, and operating procedures (rainwater harvesting systems)

Referenced standards

Sources

• UpCodes: 2024 IPC Chapter 13 nonpotable water systems (GSA adoption without amendments), https://up.codes/viewer/general-services-administration/ipc-2024/chapter/13/nonpotable-water-systems