Inside the messy, fascinating world of lavatory service.
Ever wonder what happens after you flush the toilet on an aircraft? Most of us have an inkling that the waste is whisked away to some underfloor tank, but the mechanics of it can be fascinating.
In the earliest days of flight, aircraft lavatories were low-tech. Like the systems used in railroad cars, the commodes were simply connected to a hole in the floor. Early flight crews would advise passengers not to use the facilities while aircraft were on the ground or flying over populated areas (trains of the era also closed their restrooms in and near stations for this same reason). It wasn’t just toilet waste that went overboard; early Pan American clippers used to throw galley scraps and trash overboard on transoceanic flights.
Once aircraft became pressurized and more numerous, making both holes in the aircraft and the practice of dumping waste overboard less attractive, lavatories began emptying waste into holding tanks onboard the aircraft, to be drained once they reached their destination. Earlier systems simply recirculated water from the holding tank with a blue sanitizing and odor-controlling chemical mixed in; nowadays, the toilets use a vacuum system, which doesn’t require a separate water supply (which saves weight).
I was once a ramp agent who serviced aircraft for various airlines at Anchorage International Airport (ANC), and I recall Korean Air and China Airlines flights, operated by big Boeing 747 jumbo jets, arriving in the mid-morning hours from their Asian hubs. The aircraft would have carried up to around 400 passengers for more than eight hours, and it was my job to “service the lavs” when they arrived.
Continue Reading Article After Our Video
Recommended Fodor’s Video
A Lavatory Service Truck (or “lav truck” for short) is essentially a specialized liquid hauler, with a system of hoses. Servicing the aircraft itself is pretty simple. I’d have to cover my ramp uniform in rain gear, a pair of surgical gloves, then a pair of heavy-duty rubber gloves, and a face shield. The panel underneath the aircraft is marked “Lavatory Service” and opens to a hatch around 4 inches in diameter. You connect the hose to the opening, which is covered by yet another hatch, and ensure it’s secure before releasing that hatch. Once that’s done, you can pull down on a lever which opens the last remaining barrier and empties the contents of the tank on the aircraft into the tank on the truck.
The hoses are generally a dark color so you needn’t see all the gory details of what’s coming out of the tank, but they’re still translucent enough so that you can tell the tank is still draining. On the 747, there are four tanks to drain, and they each take about five minutes to drain if they’re full. Once the tanks are all emptied, you unhook the house, close the hatch quickly, and take off in the truck.
The four tanks on a 747 will fill a lav truck almost completely, so once you’ve serviced an aircraft that big, it’s time to go dump the truck. This takes place in what is technically called a triturator, and colloquially called a “dump house.” The truck drives over an opening on the floor of the dump house, which activates the triturator which will grind anything that goes into it—sort of like a garbage disposal in a kitchen sink. A lever on the truck drains all the waste out the bottom into the grinder, where it’s then funneled into the local sewer system.
Aside from trips to the triturator, ramp agents who are “working lavs” don’t really come into contact with the effluence they’re handling, but for an extra layer of sanitation, there’s a rule—you can’t service potable water on the same day after you’ve serviced lavatories. Some union contracts pay a slight premium for agents who service lavs, even if they only do it one time per shift, so it’s common practice to assign an agent to the lav truck for their entire shift.
Lavatory sinks are a different matter. Unlike toilet waste, gray water from sinks still drains overboard through heated drain holes (to prevent them from freezing over at altitude) to convert to an icy spray which dissipates as it slowly falls to earth.
Although it’s a little-thought-of role in modern commercial aviation, the role of lavatory service is just one of the many little jobs in this labor-intensive industry. And a vital one, that keeps passengers comfortable as they jet from spot to spot around the globe.
