One of my age-old problems with various properties (rental and vacation) over many years has been gravity drains for the condensation that develops in the air-handlers of AC units. I have had apartments get major water damage, and other damage and wet carpet in other locations. One time it collected in the ceiling and drained into some kitchen cabinets.
1. AC condensation in summer is considerable, and gravity alone may not be enough to move it out of a residential air handler.
2. AC air handling units have some dust and microbes in the air and these combine to clog up lazy gravity drains -- so some action has to be taken by the home owner or service man, several times a year to prevent clogging
3. Many AC drain systems now have small electric pumps with float valves to pump the condensation out with force. But there is still the need to get the collected water in the drain pan to move the water into the pump system.
This brings me to my present research --- I have a stopped-up pan-to-pump line right now, and water is overflowing into my one of my storage rooms. So, I looked into solutions, here is what I found.
1. chlorine bleach works, but can damage glue joints in PVC pipe and smells bad, so is not advisable.
2. White vinegar works, but has the smell problem.
3. some websites suggested peroxide might work
4. finally, there are some commercial products that help and have no odor or bad other problems, Here they are:
DrainBo non toxic for all stopped up drains $6.15 at Home Depot
Pan Tablets (drop one in the drain pan regularly) Home Depot $3,48
NU Calgon Condensate Tables (similar to Pan Tablets I think)
AC Line RPS Products, SCLWHCL8 $17 delivered or in big boxes
NuLine $32 at some sources
I believe Pan Tablets, used regularly might be the long-term answer, but for initial re-establishment of water flow, I think "AC Line RPS Products" might be the better choice. Of course removing water and stoppages with shop-vac type machines might be necessary initially. I will try some or all of these and post my results later. Would love to hear your own results and products you have tried.