Not Having a Condensate Trap is Like Leaving a Window Open With the AC On

It’s hot. In fact some parts of the country are reaching record breaking temperatures right now. Everyone is trying to stay cool, but many people overlook making simple improvements to their HVAC system. One thing we encounter during many of our inspections is HVAC systems missing traps. This is basically like leaving a window open with the AC on. I’ll try to break it down for you.

What is a condensate drain trap?

A condensate drain trap is similar to the p-trap under your sinksThe traps under your sinks fill with water to stop sewer gasses from escaping the sewer and into your home. The function, or purpose, of a condensate trap depends on if the coil is under positive pressure, or negative pressure. If it’s under positive pressure (most common), it is stopping your conditioned air from being blown outside. If its under negative pressure, its preventing the condensation from pooling in your air handler which can eventually leak and cause a mess.

Are condensate drain traps required? 

There is no that specifically requires a condensate trap. However, IRC 1401.1 (we use the IRC here in Virginia) requires that “Heating and cooling equipment and appliances shall be installed in accordance with the manufacturer’s instructions and the requirements of this code”. You will be hard pressed to find an AC installation manual that does not require condensate drain traps. Below is a diagram from a Carrier AC installation manual as example. Notice that it requires that both drain lines be trapped.

are condensate drain traps required

Do I/you need a condensate drain trap if you have a condensate pump?

Yes. You need a condensate drain trap even if you have a condensate pump. Remember that the purpose of the condensate drain trap is usually to stop conditioned air from being blown outside. If you have a condensate pump the same logic still applies except that without a trap, you will be blowing conditioned air into the pump, which is usually in the crawlspace, basement, or attic. The thermal imaging video at the end of this blow demonstrates this incredibly well.

What Should I/you do if my condensate drain line clogs?

Condensate drain lines clog. If your system is installed properly this should shut off your system, or start leaking out the secondary drain which is required to be installed in a conspicuous place. Many times, it is a short pipe protruding from your soffit. Here is what to do if it clogs.