Solve Condensate and Drain Problems

Aug. 1, 2002
by Kevin V. O Keeping condensate moving away from air conditioning equipment and draining properly has always been important, but its even more so today

by Kevin V. O’Neill

Keeping condensate moving away from air conditioning equipment and draining properly has always been important, but it’s even more so today in this era of mold awareness. Here are a few simple ways to keep your customers’ systems draining the way they should.

When you turn on an air conditioner for the first time, it may be necessary to prime the trap. You can do this by pouring water into it. You can also run the air conditioner long enough to make enough condensate to fill the trap. Try to avoid using the continuous fan setting until the trap is primed. Continuous fan may not allow the condensate to flow into the trap because it is sucking air back up the drain line.

If your indoor coil or indoor unit is above a ceiling, put an emergency drain pan under the coil or unit to protect the ceiling. Run a separate drain line outside to terminate in a conspicuous location. That way, if anyone sees water dripping out of the emergency drain line, they know that there’s a problem before the ceiling comes down. It’s also a good idea to put a float switch in the emergency drain pan as insurance.

Even packaged units should have a trap. If there’s no trap on the unit, water will accumulate in the bottom of the cabinet while the blower is running, rusting the cabinet and shortening the life of the unit.

Make sure that the drain pan outlet is on the low side of the pan. I’ve been called out on drain problems where the coil was installed with the drain outlet installed pitched upwards. If the unit is installed without proper supports, it’s possible for the unit to sag, as well. Then, the water overflows the drain pan inside the unit and rusts out the bottom of the unit cabinet as well as the emergency drain pan.

Be careful that you don’t get the main drain outlet and overflow outlet mixed up on the coil. The overflow outlet is usually higher and has a dam or restriction installed inside the drain outlet.

Gas furnaces usually have the cooling coil installed on the positive pressure side of the blower. While these units seem less likely to clog, they still have their share of problems. I’ve seen such units installed in basements and crawlspaces with no trap installed. This allows cold or hot supply air to blow out into unconditioned spaces through the condensate drain.

Service Tips

When you go on a service call for a clogged drain line, the first thing I recommend you do is vacuum the line from the termination end with a wet/dry vacuum. I know some contractors who blow the line out with reasonable success, but that blows the clog back into the drain pan. If you vacuum the drain line, all the algae, slime, dirt, rust and other debris in the drain line and near the outlet in the drain pan are removed from the drain system. The nice thing about vacuuming from outside is that you don’t have to carry the vacuum sweeper through the customer’s house. This reduces the chance that you might spill dirty, slimy water on their clean carpet.

If you blow the line from the outside, that stuff all ends up in the drain pan where it can flow out into the drain line again, causing another clog. Then you have to clean it out again (for free), or maybe lose a customer.

You can also install a cleanout between the drain pan and the trap and blow the line out from there, but that doesn’t clean anything out of the drain pan. If you blow the line out with a high-pressure gas such as nitrogen, the advantage is that you should get even the most difficult clogs. Sometimes a vacuum sweeper isn’t powerful enough for really tough clogs. Remember to always cap or plug the cleanout when you’re not servicing the drain.

The next thing to do is replace the trap. During the winter, any debris in the bottom of the trap can dry out and harden. This leaves a smaller opening in the trap for condensate to flow through. Replacing the trap restores it to full diameter.

After you’ve cleared the line, add an algaecide. I commonly use 10 pan pills for a clogged drain service call on residential size units. For preventive maintenance calls, two to four pan pills is usually enough. Some companies make large volume or long-lasting pan treatments. These are useful if the drain pan is large enough to hold them. In extreme cases, I have used plumber’s drain cleaner on callbacks. Be careful that the discharge is diluted at the outlet so that children or pets don’t get burns. I’ve also tried bleach as a way to kill algae growing in drain lines, but it doesn’t work as well as slow-dissolving tablets.

Finally, explain to your customers that they need to call you if they see water dripping out of the emergency drain line. This way, you can handle the problem before the customer has a wet ceiling and is unhappy with you.

Kevin V. O’Neill is the owner of O’Neill Cooling & Heating, Myrtle Beach, SC. He can be reached at 843/385-2220.