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

Plumbing Code

Delaware follows the International Plumbing Code (2021 edition).

The IPC (International Plumbing Code) is maintained by the International Code Council (ICC) and is adopted by approximately 35 states. It covers water supply, drainage, fixtures, and cross-connection control.

Backflow Prevention Testing

Annual testing is required in Delaware 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 Delaware.

• Licensed plumber required: Yes
• Homeowner can DIY: No - licensed plumber 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

Delaware 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

Delaware 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 Delaware 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 Delaware. 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

• Delaware 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