30″ x 30″ x 4” Square Water Heater Drain Pan with 1″ Adapter

30” × 30” × 4” 24 Gauge Galvanized Steel Water Heater Drain Pan

The WSG403030 is a 30” × 30” × 4” square water heater drain pan manufactured from 24 gauge galvanized steel (0.0276″ thick), designed to collect slow water heater leaks and protect sub-floors and structural framing from moisture damage. A pre-installed 1” female NPT drain adapter on the short side accepts direct connection to ¾” or 1” gravity drain piping — no drilling or secondary fittings required.

The 4” depth provides substantial leak containment capacity and is the most common specification for residential and light commercial water heater installations. The 30” × 30” interior floor fits large-capacity commercial water heaters and 75-gallon or 100-gallon tank units. The outer rim (top opening) measures 32″ x 32”, flanging outward to allow the water heater base to seat fully inside the pan without contacting the walls.

Suitable for residential and commercial installations wherever the International Residential Code (IRC Section P2801.5 / P2801.6) or International Plumbing Code (IPC Section 504.7) requires drain pan protection beneath an indoor water heater.

Plumbing Code Requirements

International Residential Code — IRC Section P2801.5 (2024) / P2801.6 (2021 and Prior Editions)

IRC Section P2801.5 (2024 edition) and Section P2801.6 (2021, 2018, 2015, and prior editions) require a drain pan beneath any storage tank-type water heater installed in a location where water leakage from the tank will cause damage. This typically mandates pans in attics, crawlspaces, interior closets, upper floors over finished living spaces, and any indoor location where a leak could reach and damage occupied areas. Garages and unfinished basements may be exempt depending on local amendments.

Code-required pan construction materials include galvanized steel or aluminum at a minimum thickness of 0.0236 inches (0.6010 mm), or plastic at a minimum thickness of 0.036 inches (0.9 mm). A plastic pan beneath a gas-fired water heater must additionally meet a flame-spread index of 25 or less and a smoke-developed index of 450 or less per ASTM E84 or UL 723. The WSG403030 is manufactured from 24 gauge galvanized steel at 0.0276″ thick, exceeding the 0.0236″ minimum for metal pans with no flame-spread restriction.

The pan must be at least 1½ inches (38 mm) deep and large enough to catch dripping or condensate from the tank. The drain must connect to an indirect waste pipe with a minimum diameter of ¾ inch (19 mm). The T&P relief valve discharge line must remain independent from the pan drain line — they cannot be interconnected. The drain pipe must extend full-size and terminate over an approved indirect waste receptor or to the exterior of the building, between 6 and 24 inches above the adjacent ground surface.

View IRC Section P2801.5 on iccsafe.org

International Plumbing Code — IPC Section 504.7

Under the International Plumbing Code (IPC), Section 504.7 in Chapter 5 (Water Heaters) governs drain pans consistently across the 2018, 2021, and 2024 editions. A pan is required whenever a storage tank-type water heater is installed indoors where water leakage will cause damage to the building or its occupants. Approved materials match the IRC: galvanized steel or aluminum at 0.0236″ minimum, or plastic at 0.036″ minimum. The IPC explicitly states that a plastic pan shall not be installed beneath a gas-fired water heater unless it meets strict flame-spread indices; this restriction does not apply to galvanized steel pans.

IPC Section 504.7.1 requires a minimum 1½” pan depth and ¾” minimum indirect waste pipe. IPC Section 504.7.2 governs drain termination. A replacement exception in recent IPC editions allows omitting a new drain line where structural conditions make it impractical — many jurisdictions substitute an automatic water shut-off valve or moisture alarm in those retrofit cases.

View IPC Section 504.7 on iccsafe.org

When Is a Drain Pan Required?

Building inspectors typically require a drain pan when a water heater is installed in a finished living space, attic, garage above a living space, utility closet within the conditioned envelope, or any location where a leak could flow to and damage occupied areas. Many commercial mechanical codes extend this requirement to all indoor installations. Plumbing and mechanical inspectors routinely verify pan installation and drain pipe routing at rough-in inspection. Always confirm the locally adopted code edition and any local amendments with the authority having jurisdiction (AHJ) for the installation address.

Compatible Water Heater Applications

Residential Gas and Electric Tank Water Heaters

The 30” × 30” interior floor accommodates large-capacity commercial water heaters and 75-gallon or 100-gallon tank units. Always measure the actual water heater base at its widest point — include any legs, control valves, or mounting flanges. The base must fit within the 30” × 30” interior opening; allow ½” to 1” clearance on all sides for comfortable placement.

Light Commercial Water Heaters

Commercial storage water heaters with larger or non-standard base footprints may require a correspondingly larger pan. If the water heater base approaches the interior pan dimension, use the next larger pan size. Verify the local authority having jurisdiction does not specify a minimum pan wall height greater than 1½”.

Solar and Heat Pump Water Heaters

Solar storage tanks and heat pump water heaters with oversized or irregular base profiles require careful measurement before selecting a drain pan. The tank base must clear the pan interior walls. Consult manufacturer installation instructions for accessory base dimensions not reflected in the nominal tank capacity rating.

Installation Instructions

Before Installing

• Turn off the water heater fuel supply (gas shutoff valve) or circuit breaker before moving the unit
• Drain the tank partially or fully if relocating an existing unit — a full 50-gallon tank weighs over 400 lbs
• Verify the floor beneath the installation area is level and rated for the loaded weight of the water heater
• Plan the drain piping route before placing the pan — the NPT adapter orientation must face the drain direction

Installation Steps

1. Place the drain pan in the installation location with the drain adapter oriented toward the planned drain piping route
2. Wrap the drain adapter threads with PTFE tape and hand-tighten a ¾” or 1” fitting; finish with 1–2 turns with a wrench — do not over-torque polymer threads
3. Run the drain line with a continuous ¼” per foot minimum downward slope to an approved indirect waste receptor, floor drain, or exterior discharge point; do not trap the drain line
4. Lower or slide the water heater carefully into the pan using an appliance dolly or two-person lift — do not drop or impact the pan
5. Verify the water heater sits level inside the pan; the base should not contact the pan walls
6. Reconnect plumbing, gas supply, relief valve piping, or electrical connections per the water heater manufacturer instructions and local code
7. Fill the tank completely and check all connections for leaks before restoring power or gas supply

Drain Line Notes

The drain line must terminate at an approved indirect waste receptor, visible floor drain, or code-compliant exterior discharge location — never terminate in a sealed space. Do not install a trap on the drain pan line. In attic installations, the IPC requires the overflow drain to be piped to a visible location where leakage is immediately apparent, such as a full-port valve above an exterior soffit.

Frequently Asked Questions

What is a water heater drain pan?

A water heater drain pan is a shallow basin installed beneath a tank-type water heater to collect slow leaks, condensation, and overflow. The pan connects to a drain pipe that routes collected water safely away from the structure, preventing moisture damage to sub-floors, framing, insulation, and finished surfaces below the installation area.

What size drain pan do I need for my water heater?

Measure the outer base footprint of your water heater at its widest point, including all legs and protruding controls or flanges. Select a drain pan with an interior floor dimension at least equal to that measurement. The WSG403030 has a 30” × 30” interior floor with a 32″ x 32” outer rim — suitable for water heaters with a base footprint of 30” × 30” or slightly smaller.

How deep does a water heater drain pan need to be?

IRC and IPC both require a minimum of 1½” side height. The WSG403030 provides 4” of depth, which provides substantial leak containment capacity and is the most common specification for residential and light commercial water heater installations.

Does the drain pan need to be connected to a drain?

Yes — per IRC P2801.5 / P2801.6 and IPC Section 504.7, the drain pan must connect to a drain pipe terminating at an approved indirect waste receptor or code-approved location. An unconnected pan fills and overflows, providing no protection once capacity is exceeded. Building inspectors verify the drain connection at rough-in in most jurisdictions.

What material is this drain pan made from?

The pan is manufactured from 24 gauge galvanized steel at 0.0276″ thick. Galvanized steel is a code-approved material for water heater drain pans — the zinc coating provides corrosion resistance in wet environments, and 24 gauge at 0.0276″ exceeds the 0.0236″ minimum thickness required by both IRC P2801.5 / P2801.6 and IPC Section 504.7 for metal drain pans.

Can this pan be used under a gas water heater?

Yes. The WSG403030 is manufactured from galvanized steel, which is approved for use beneath both gas and electric tank-type water heaters with no flame-spread or smoke-development restrictions. Unlike plastic pans, galvanized steel pans carry no additional code restrictions for gas-fired applications. Ensure the flue connector, gas supply line, relief valve discharge piping, and required combustion air clearances are established after the pan is in position per the water heater manufacturer instructions and local mechanical code.

What is the outer rim (top opening) dimension?

The outer rim top opening of the WSG403030 measures 32″ x 32”. The rim flanges outward above the 30” × 30” interior floor, allowing the water heater base to rest inside the pan. Always verify the water heater base footprint clears the 30” × 30” interior opening before ordering.

Where should the drain pan drain line terminate?

The drain line must terminate at an approved indirect waste receptor, floor drain, exterior discharge location, or other point accepted by the authority having jurisdiction. The line must maintain a continuous downward slope of at least ¼” per foot with no traps. Attic installations must route the drain to a visible location where leakage will be noticed promptly.