AS9120B, ISO 9001:2015, and FAA AC 0056B ACCREDITED

Water and Waste Systems in Aircraft

In aircraft, the water and waste system is designed to provide water for the galley and lavatories. Generally, the water and waste system completes three major processes: filling water on land, providing it during flight, and storing toilet waste until landing. To effectively accomplish these tasks, a number of different components are used, including several pumps, storage tanks, valves, and more. Besides satisfying one’s curiosity, having a basic understanding of how these mechanisms work together can be helpful to aircraft operators for spotting and troubleshooting potential issues in their vessel.

Water System

Generally, the water and waste system can be split into two major parts, wherein one system stores and distributes fresh water, while a different system deals with the wastewater generated onboard. The potable (drinkable) water system delivers clean water to every needed part of the plane, including the kitchen sinks and lavatories. Similar to the air in the cabin, the fresh water stored in aircraft must also be pressurized, as the high pressures of the surrounding air can make the water evaporate much more easily than on the ground. To accomplish this, an air inlet pumps a certain amount of oxygen in the tank to maintain the proper pressure.

Consequently, the tank is never filled to its maximum capacity and must instead be closely monitored to keep a certain amount. For this reason, a smart fill/overflow valve is used to prevent an overflow if the amount of water in the tank surpasses the set limit. After leaving the potable water tank at the tail end of the aircraft, the water is siphoned into a pipeline and sent to areas like the toilet rinse valve, water heater, and galley sink valves. Before leaving the tank, a water quantity transmitter communicates the necessary information to the valve system to transfer the correct amount of fluid.

Waste System

A common question for aircraft passengers is where the waste goes. Despite a popular rumor that all of it is simply thrown overboard, the waste is separated into two types that are dealt with differently. During flight, the wastewater from the sinks is disposed of overboard where it evaporates long before even approaching the ground. Conversely, the waste coming from the laboratories is moved to a waste tank where it is stored until landing. In addition to a storage tank, the lavatory waste system typically includes a waste service panel, waste drain valve assembly, and finally, a waste tank rinse fitting assembly that cleans the waste tank to prevent bacteria buildup.

Process Overview

Starting when the toilet is flushed, fresh water coming from the water system previously discussed enters the toilet through a modeled valve to control the flow. Then, the contaminated water flows through a series of pipes and into the waste tank where it will remain until the plane lands. Once on the ground, the next step is to discard the wastewater and rinse the waste tank. First, a large hose is connected to a waste collector via the waste service panel assembly. Using powerful suction, the collector siphons in all the wastewater to be discarded and eventually sent to a treatment plant. The now empty waste tank is then rinsed with a mixture of cleaning product and water that is injected from the rinse fitting assembly. Once fully cleaned, the tank can be closed and used again on the next flight without worry of bacteria build-up in the system.


Though aircraft do not depend on their waste and water system to fly, all aboard the aircraft rely on it for a comfortable and sanitary flight experience. With an inventory of over 2 billion new, used, obsolete, and hard-to-find items in our inventory, Aerospace and Defence Parts is ready to assist you with all the aircraft parts you require. As the leading distributor of water and waste supply system components in aircraft, we guarantee a dependable selection of parts that have been quality-tested and sourced from leading global manufacturers, including Boeing, Airbus, and many other industrial leaders. For example, the part number 38000-310 from Monogram Systems is among the high-quality components we offer. Begin the purchasing process today when you use our Instant RFQ service; our team of experts is available 24/7x365 to answer customer inquiries and requests!


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