USA Expert Plumbing

Water heater drain pan: is it required

By USA Expert Plumbing Editorial Team. Updated . 1 min read.

Short answer

Under the International Residential Code, a drain pan is required where a leaking tank water heater would cause damage, such as in attics, upper floors and finished spaces. The pan must be at least 1.5 inches deep with a drain line at least 3/4 inch in diameter to an approved location. Local codes vary, so check with your building department.

In this guide
  1. When a pan is required
  2. Pan and drain line requirements
  3. Choosing a pan
  4. A pan is not enough by itself
  5. Installing a pan

A drain pan is a shallow tray under a tank water heater that catches leaks and routes them away before they soak floors and ceilings.

When a pan is required

The International Residential Code, which many U.S. jurisdictions adopt, requires a pan where a storage tank water heater is installed in a location where leakage would cause damage. That typically means:

  • Attics and upper floors
  • Finished basements and closets inside living space
  • Any spot where water would reach drywall, flooring or ceilings below

Local codes and amendments vary, and some areas require pans in more places. Your building department or plumber can confirm.

Pan and drain line requirements

ItemTypical IRC requirement
Pan depthAt least 1.5 inches
Drain line sizeAt least 3/4 inch diameter
Where the drain goesTo an indirect waste receptor, floor drain or outside, per local code
Pan materialGalvanized steel, aluminum or approved plastic suitable for the heater

Choosing a pan

  • Pick a diameter a few inches wider than the heater base.
  • Use a metal pan under gas heaters if your code or manufacturer requires it.
  • Choose a pan with a drain fitting that matches your drain line.

A pan is not enough by itself

A pan without a drain line only holds a small amount of water. For extra protection, add a leak sensor or an automatic shutoff valve; see our leak detection system cost guide. Pans are easiest to add during a replacement; see our water heater replacement cost guide.

Installing a pan

  1. Turn off the heater and the cold water supply, and drain the tank.
  2. Disconnect the water, gas or electrical connections as needed.
  3. Lift the heater, set the pan in place and set the heater back in the center.
  4. Connect the pan's drain line and run it to an approved location.
  5. Reconnect everything, refill the tank with a hot tap open, and restore heat.

Because full tanks are very heavy, this is usually a two-person job or a plumber's job.

Common questions

Do I need a drain pan for a water heater in a garage?

Many garage installations on a slab do not require one, but local codes vary. A pan is still cheap protection.

Can a drain pan be added to an existing water heater?

Yes, but the heater must be drained and lifted, so it is easiest during a replacement.

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