Combining the water heater and a/c drains is not allowed by the International Residential Code (IRC) and the Residential Edition of the Florida Building Code [FBC P2804.6.1(4)]: "The discharge piping serving a pressure-relief valve, temperature-relief valve or combination valve shall serve a single relief device and shall not connect to piping serving any other relief device or equipment."

    One of the worst examples of combining the water heater TPR drain with the air conditioning condensate drain that we saw a few years ago was a condensate drain that terminated into the catch pan and drain of a water heater located below it. The water heater catch pan is not meant to have water dripping into it continuously and, as a result, the base of the water heater was badly corroded. Don’t do it. 

    To learn more about the TPR drain from a water heater, see our blog post What are the code requirements for the discharge piping from a Temperature-Pressure Relief (TPR) valve at a water heater?

• • • • • • • • • • • • • • • • • • • • • • • • • • • • 

  To learn more about heating and air conditioning systems, see these other blog posts:

• How can I find out the SEER of my air conditioner? 

• My air conditioner won't turn on. What's wrong? 

• How can I find out the size of my air conditioner? 

• How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump? 

• Where is the air filter for my central air conditioner and furnace? I can’t find it? 

• Does an old air conditioner use more electricity as it ages? 

• How did homes stay cool in Florida before air conditioning? 

• What is wrong with an air conditioner when the air flow out of the vents is low?

• Why has the thermostat screen gone blank? 

• Why does it take so long to cool a house when an air conditioner has been off for a while? 

• Why is my air conditioner not cooling enough? 

• What are the most common problems with wall/window air conditioners?  

• Will closing doors reduce my heating and cooling costs? 

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