有時候在停機坪上，我們會看到飛機機身下方有水排出，直接流到地面。那些水到底是什麼呢？
其實，飛機上的用水大致可以分為四類：
1. 飲用水（Potable Water）
這是供應給乘客飲用、沖泡飲品，以及廚房（Galley）使用的乾淨水源。它儲存在專用的飲用水箱中，由地勤人員透過加水口補給。只有在維修更換或水太滿時，才會經由飲用水專用的排放口排出。
2. 灰水（Gray Water）
來源主要是飛機洗手間裡面洗手盆與廚房使用過的水。這些水會透過管路集中到排水桿（Drain Mast），再排到機外。排水口通常位於飛機腹部或尾部。由於飛機在空中也可能排放灰水，因此這些排水口都設有加熱裝置，避免高空結冰。
3. 空調冷凝水（Air Conditioning Water）
當空調系統運作時，會將空氣中的濕氣冷凝成水滴，並透過排水口排出。此外，輔助動力裝置（APU）在運轉時，也會產生冷凝水，同樣需要透過 APU 專用的排水口排放。延伸閱讀：《知識》飛機的輔助動力系統 (Auxiliary Power Unit, APU)
4. 廁所污水（Lavatory Waste）
飛機真空廁所產生的污物，會被集中儲存在密閉污水槽裡。這些污水在飛行途中不會排放到外面，而是等到落地後，由地勤人員透過清潔車抽走，並同時清潔與補充藍色消毒液。
如果下次在停機坪上看到飛機機身下方有水排到地面，那些通常是灰水或空調冷凝水。
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Why Do Airplanes Drain Water On The Ground? What Is That Water?
Sometimes, you might see water coming out from under an airplane and flowing onto the ground. So, what exactly is that water?In fact, the water on an airplane can be divided into four main types:
1. Potable Water
This is clean water for passengers to drink, make beverages, and for use in the galley (kitchen). It is stored in special tanks and filled by ground staff through a water port. It is only drained when the tank is too full or needs maintenance.
1. Potable Water
This is clean water for passengers to drink, make beverages, and for use in the galley (kitchen). It is stored in special tanks and filled by ground staff through a water port. It is only drained when the tank is too full or needs maintenance.
2. Gray Water
This comes from sinks in the lavatories and from galley use. The water is collected through pipes and released outside through a drain mast, usually located under the belly or at the tail of the airplane. Since gray water can also be released in flight, the drain outlets are heated to prevent ice from forming at high altitudes.
3. Air Conditioning Water
When the air conditioning system runs, it turns moisture from the air into water droplets, which are drained outside. The auxiliary power unit (APU) also produces condensation that is drained through its own outlet.
4. Lavatory Waste
Waste from the airplane’s vacuum toilets is stored in sealed tanks. This waste is never released during flight. Instead, after landing, ground staff remove it using a service truck and refill the system with blue disinfectant liquid.
So, the next time you see water dripping from an airplane, it’s most likely gray water or condensation from the air conditioning system.
This comes from sinks in the lavatories and from galley use. The water is collected through pipes and released outside through a drain mast, usually located under the belly or at the tail of the airplane. Since gray water can also be released in flight, the drain outlets are heated to prevent ice from forming at high altitudes.
3. Air Conditioning Water
When the air conditioning system runs, it turns moisture from the air into water droplets, which are drained outside. The auxiliary power unit (APU) also produces condensation that is drained through its own outlet.
4. Lavatory Waste
Waste from the airplane’s vacuum toilets is stored in sealed tanks. This waste is never released during flight. Instead, after landing, ground staff remove it using a service truck and refill the system with blue disinfectant liquid.
So, the next time you see water dripping from an airplane, it’s most likely gray water or condensation from the air conditioning system.
