All split HVAC systems have a condensate drain line. To help prevent the drain line from clogging and backing up you can simply add a half cup to a full cup of vinegar into the drain line of the indoor unit. This will help break down sludge build up. Do not add any harsh chemicals such as bleach, chlorine, etc. Most units will have an access point to pour the vinegar into. If there is no access point it could be added in most cases, but it is better left to a professional to be installed. As this is not a cure all for drain issues, it will help reduce the possibility of your drain line backing up and causing water damage.