Data sources: State plumbing boards, ICC, IAPMO, EPA Last verified: 2026-03-17

Plumbing Code

Hawaii follows the Uniform Plumbing Code (2018 edition).

The UPC (Uniform Plumbing Code) is maintained by IAPMO (International Association of Plumbing and Mechanical Officials) and is primarily used in western states. It covers similar topics to the IPC with some differences in pipe sizing and fixture requirements.

Backflow Prevention Testing

Annual testing is required in Hawaii for testable backflow prevention assemblies (RPZ, DCVA, PVB).

• Residential: May be required for homes with irrigation systems or other cross-connections; check local water-supplier rules
• Who can test: Certified tester
• Enforcement: Local water utility

Water Heater Installation

A permit is required to replace or install a water heater in Hawaii.

• Licensed plumber required: Yes
• Homeowner can DIY: No - licensed plumber required
• Seismic strapping: check local code for whether your water heater must be secured with upper and lower straps
• Note: Seismic strapping required

Universal requirements (all states):

• Temperature & Pressure Relief (TPR) valve must be installed
• Discharge pipe from TPR must terminate safely
• Gas water heaters: proper venting required
• Gas water heaters in garages: an 18" elevation of the ignition source above the floor may apply, subject to equipment exceptions and local code
• Expansion tank often required when backflow preventer is installed on main supply

Homeowner DIY Plumbing Rights

Hawaii requires a licensed plumber for plumbing work. Check whether a homeowner exemption applies to plumbing on your own residence; permits and inspections are usually still required.

Licensed plumber required

Water Conservation Requirements

Hawaii follows federal water conservation minimums (no additional state mandates).

Federal minimums apply

Lead Service Line Replacement

Under the EPA Lead and Copper Rule Revisions (2021), water systems in Hawaii must inventory service lines; the Lead and Copper Rule Improvements (2024) add requirements to replace lead service lines. Ask your water system for its inventory and replacement plan.

Important Disclaimer

This information is provided as a general overview. Plumbing codes and regulations can vary significantly between municipalities within Hawaii. Always check with your local building department before starting any plumbing work. Local codes override state minimums - your city or county may have stricter requirements.

Sources

• State plumbing boards and licensing agencies
• International Code Council (ICC) - IPC adoption map
• International Association of Plumbing and Mechanical Officials (IAPMO) - UPC adoption
• Manual de control de conexiones cruzadas de la EPA (guía de la Ley de Agua Potable Segura)
• State building departments

Sources

• Hawaii state plumbing board and licensing agency
• International Code Council (ICC) - IPC adoption map
• International Association of Plumbing and Mechanical Officials (IAPMO) - UPC adoption
• EPA Cross-Connection Control Manual (Safe Drinking Water Act guidance)
• State and local building departments