[True Story] Discovered by my wife's scream! Water gushing from the air conditioner... How I fixed a summer drain clog myself

It started with a "scream" that night
That night, after finishing dinner as usual, I was just idly watching TV.
I heard my wife scream from the laundry room.
"Hey! The water!"
I rushed over in a panic, and an unbelievable sight unfolded before me. Water droplets were cascading down from around the air conditioner's vent like a small waterfall. It wasn't just dripping; a puddle had already started to form on the floor.
Honestly, my heart sank. "Is it broken?" "It's bad if water gets into the circuit board." "The floor might get damaged." Various anxieties swirled through my head.
There must be many people who have had a similar experience, or who are feeling uneasy thinking, "My air conditioner has been acting a bit strange lately too." Especially during this season, trouble is inevitable for air conditioners running at full capacity.
Today, based on our family's real experience, I would like to share as concretely as possible how to identify the cause, the emergency measures I actually took, and how to prevent the same thing from happening in the future. This is a record from the perspective of an ordinary person, not a professional technician. I hope it serves as a hint to help you respond a little more calmly if you ever find yourself in the same situation.

Investigating the cause and what I actually did
First, I suspected a "drainage clog"
Seeing the water leak, the first hypothesis that came to mind was, "Is something in the drainage path clogged?"
When an air conditioner is in cooling mode, moisture in the air condenses inside the indoor unit. This condensation is designed to be discharged outdoors through a thin tube called a drain hose. Conversely, if this drainage doesn't work well, the water that has lost its way will back up into the room and appear as a leak.
In fact, this "drain hose clog" is considered the most common cause of water leaks. The causes are mainly dust and dirt accumulated inside the hose, or insects and fallen leaves that have entered from the outside. It is said that especially in households with pets or in environments where humidity easily builds up, like an LDK (living/dining/kitchen area), slime (slimy dirt) is likely to form and accumulate, increasing the risk of clogging.
So, I decided to go out into the garden and check the back of the outdoor unit.

Checking the back of the outdoor unit confirmed my suspicion
The outlet of the drain hose is located at the back of the outdoor unit. When I looked at it while shining a flashlight, as expected, no water was coming out at all. The place where it should have been dripping was completely dry.
I judged that there was a high possibility that a clog had occurred somewhere along the way. By the way, the cause of a water leak is not limited to a clogged drain hose. It seems there are cases where the hose is too long or bent, or where the high airtightness of the house prevents proper drainage due to the pressure difference between the indoors and outdoors. However, this time, I judged that it was highly likely to be a clog based on the situation where no water was coming out of the hose outlet at all.

Clearing the clog with a suction pump
Once I had made my assessment, I immediately headed to the storage shed. I pulled out a "drain hose suction pump" that I had prepared just in case. This is a tool for home emergency use that you insert into the drain hose outlet and use to suck out dust and dirt clogged inside, either manually or electrically. It can be purchased for a few thousand yen at home centers or online. (See the image below)
I set the pump at the tip of the hose and nervously tried to suction it—
Gurgle, gurgle!
Along with murky water, a lump of dirt-like material came out all at once. Honestly, I hadn't expected such a clear result, so while I was a little surprised, the sense of relief that I had identified the cause was greater.

Restarting and monitoring
After clearing the clog, I nervously tried restarting the air conditioner. I let it run for a while and watched the indoor unit, but that waterfall-like leak had stopped completely. I was also able to confirm that water was being properly drained from the drain hose outlet.
As a result, it is thought that this case was caused by "backflow due to a clogged drain hose." Although it was an emergency measure, being able to identify and deal with the cause myself saved me from unnecessary expenses and an anxious night.

"Preventive measures" learned from this experience
What I felt again through this incident is that you can reduce the risk of air conditioner water leaks with a little daily mindfulness, rather than "panicking after it happens."
• Regularly check the drain hose outlet visually (especially between the end of the rainy season and before the full-scale midsummer season)
• Check if fallen leaves or trash have accumulated around the outdoor unit
• Clean the filters frequently so that dust does not accumulate inside the indoor unit
• If you hear any concerning strange noises (popping or tapping sounds), it might be a sign of poor drainage due to pressure differences, so have it inspected early
• Keep one suction pump for drain hoses on hand
These are all things that anyone can start doing today without any special knowledge. Of course, if the problem does not improve even after clearing the clog, or if you suspect structural causes such as the indoor unit being tilted or installed incorrectly, it is safer to consult a professional without pushing yourself. I felt that it is also important not to put it off by saying "I'll wait and see," because leaving a water leak unattended can lead to secondary damage that harms household goods such as floors and walls.

Trouble can be turned into "preparation" for the next time
Honestly, this incident, which started with a scream in the night, made me quite flustered. But looking back, by not panicking and searching for the cause in order, and checking one by one, I was able to reach a solution faster than I thought.
Trouble at home always comes suddenly. However, I realized once again this time that by knowing the cause and having the minimum tools and mindset, you can respond without panicking.
If you are reading this and are currently in a similar situation and troubled—first, please check the back of the outdoor unit and the drainage outlet. Just doing that should give you a clue as to what to do next.
And for those who haven't had anything happen yet, I recommend checking the condition of your drain hose once before the peak of summer arrives. A little inspection might prevent a scream on a midsummer night.
I hope our family's small trouble leads to someone else's "preparation."