Every major manufacturer of tankless water heaters specifies that a catch pan and drain piping be installed under the unit if leakage would cause damage to the immediate area, and that is certainly the case when one is installed in an attic. Also, the International Residential Code (IRC) requires that a drain pan be installed “where leakage of the tanks or connections will cause damage.” A tankless obviously does not have a storage tank, but it does have pipe connections that can leak as the unit reaches the end of it serviceable lifespan. So a drain pan is definitely required for attic installation. 

    One hapless plumber, or perhaps a handyman masquerading as a plumbing expert, installed the drain pan (shown in the photo above) under an attic tankless water heater in a home we inspected today. Yes, it is a drain pan and it is under the water heater, but the TPR valve drain piping was routed through a roughly cut-out hole in the side of the pan, so the pan will immediately leak when water drips into it and it has no drain to exterior even if it was watertight. This would be a good example of how NOT to install an attic drain pan.

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Here’s links to a collection of more blog posts about WATER HEATERS:

• Are water heaters required to be raised off the floor? 

• Can a Temperature and Pressure Relief (TPR or T&P) valve be mounted to discharge horizontally?

• Where are gas water heaters not allowed to be installed?  

• Is the minimum size water heater inlet pipe 1/2" or 3/4" according to the building code? 

• What is required clearance for access and working space in front of an electric water heater? 

• Why is the water heater older than the house? 

• Why is there water in my water heater drain pan?

• What does it mean when a water heater Temperature/Pressure Relief (TPR) discharge pipe is "trapped"? 

• Can I leave a gas water heater in place when remodeling a garage into a family room or bedroom? 

• Where do I find the water heater in a mobile home?

• Does a tankless water heater in an attic require a drain pan? 

• Does an electric water heater require a disconnect? 

• Is a catch pan and drain piping required for a replacement water heater?

• What is the difference between a single element and dual element electric water heater? 

• What are the most common installation mistakes with water heater replacement?

• Why is my water heater making strange (rumbling, gurgling, knocking or banging) noises? 

• What can I do to make my water heater last longer?

• How can I determine the age of a water heater if the serial number is missing or decoding it is impossible? 

• How does a hydronic heating system work?

• What is the difference between a regular water heater and a direct vent water heater? 

• What is the difference between a regular water heater and a power vent water heater?

• What is backdrafting at a gas water heater? 

• How do I determine if a water heater is gas or electric?

• What does it mean when a gas appliance (water heater, furnace, or range) has been "red tagged"?  

• What's the valve with the flip-up handle on the water heater for?

• Why is an older water heater an insurance problem?

   Visit our WATER HEATERS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.