One of these issues is water leaking into a home; in most cases, it needs to be set up to drain better.
A window air conditioner unit should be level, and some people have it lean slightly away from a house, so the water drains away better.
This can be beneficial, especially in a big rainstorm when lots of water has a problem quickly draining from the outer case.
Sealing the outer case where it meets the wall is important and can be done in a variety of ways, with most using outdoor calking.
The inside of the outer case must drain well, or water can back up and enter a home.
All units will have some type of drain plug that may simply be clogged and need to be cleaned to drain properly.
If you live in a very rainy environment, extra holes can be drilled into the bottom of the outer case to help water flow out.
If holes are drilled into a unit, be very careful of the internal components, as damaging any internal components will make the unit unusable.
If extra drain holes are drilled into the case, it is best to go at an angle as not to drill into any components or refrigeration lines.
Most often, simply cleaning the unit from any debris as regular maintenance should be enough, and new holes are only needed in extreme cases.
Since all units are different, sometimes the drain can be located in the wrong spot during an install, in which case a new hole would be necessary.
There are also small attachments that create a roof over a unit that shields it from extreme rain, which also works well in many scenarios.
Every install can vary since the many window A/C units available and how a home window is built must be taken into consideration.
Good sealant, bigger drain holes, and possibly a small roof cover for a unit are all options.
Proper maintenance is also a big factor to help an A/C unit drain properly and run smoothly and quietly.