Waste Tank Maintenance

Guide to Proper Waste Tank Maintenance of Restroom Trailers

Getting Started

Regular maintenance of the waste tanks of restroom trailers ensures proper functionality and helps to avoid unwelcome odors during use. Before every customer reservation, the waste holding tank of a restroom trailer must be what’s referred to as "charged." This means that the bottom of the waste tank should be covered with approximately 10% of the waste tank capacity, with fresh water and treated with deodorizing packets. These packets typically follow the recommendation of one packet per toilet.

An appropriate charging scale for restroom trailers is as follows:

Restroom Trailer Tank Sizes
  • 200 gallons = 20 gallons water
  • 300 gallons = 30 gallons water
  • 350 gallons = 35 gallons water
  • 480 gallons = 50 gallons water
  • 520 gallons = 50 gallons water
  • 750 gallons = 75 gallons water
  • 1000 gallons = 100 gallons water
To adequately charge a restroom trailer waste tank, we suggest following the detailed procedure below:
  1. After the restroom trailer is set in place at the event site, leveled, and blocked, open the lid of the freshwater tank located in the mechanical room and insert a garden hose, or connect the the city water connect and open Valve 3, Fresh Water Fill. 
  2. Ensure all valves at the bottom of the tank are closed before turning on the weather supply.
  3. After turning on the available water supply, fill the waste tank using the incremental gallon scale on the side of the tank to the desired amount as seen above on the charge scale.
  4. When the tank is filled to the desired amount, turn off the water supply.
  5. With the water supply turned OFF, open the main tank and Drain to waste tank valve. The measured amount of water in the fresh water tank will drain into the waste holding tank giving you the exact amount needed to properly charge the restroom waste tank.
  6. When the freshwater tank is empty, close the Drain to Waste Tank Valve. 
  7. At this point, you can drop the recommended number of tank deodorizers into the toilets as described above through the toilets. The waste tank is now charged and ready for use at the reservation location.

Emptying the Waste Tank

At the end of the rental event, the waste tank and fresh water tank must be pumped and drained before moving the trailer. There are just three steps necessary to accomplish this. As not all installations are the same there may be some slight differences or variations in performing this procedure. Generally, the three steps required to properly empty a restroom waste tank are tipping, draining, and pumping.

  1. Tipping means to lower the front of the trailer allowing the liquids to flow to the front of the trailer where the waste valve is located.
    • This is done by raising the front stairs and both front stabilizer jacks. This will allow the nose of the trailer to go lower with the use of the tongue jack. As the trailer tips forward liquids will relocate closer to the waste valve and allow for easier emptying. 
  2. The second step in emptying a restroom trailer is adequate draining of the freshwater tank. At this time if there is water in the fresh water tank, open the drain valves labeled Drain to Waste Tank or Drain Fresh Water to Ground. 
  3. Also known as waste removal, pumping or evacuating the waste tank is the third step to properly emptying a restroom trailer. 
    • Connect the pump vacuum hose to the dump valve and begin evacuating the waste.
    • Using the tongue jack, lower the nose of the trailer as low as possible allowing the waste to run toward the front of the trailer. When finished evacuating the restroom trailer waste tank, close the dump valve, remove the evacuation hose, and raise the trailer to the proper towing height.

Cleaning The Waste Tank

While it is not required to flush the tank after every use we strongly recommend that this process is completed at least once a month.

After the waste holding tank has been emptied but before disconnecting the evacuation hose, connect a hose from a freshwater source to the tank wash-down gun. Once connected, insert the gun into the toilet in the rear of the restroom by stepping on the flush pedal on the toilet to open the flush ball. Once the flush ball is open you can insert the gun into the toilet and gently push it to the bottom of the tank and turn it on.

While keeping the spray nozzle on the bottom of the tank, rotate the gun in a fan motion so the water spray hits all four walls of the restroom trailer waste tank. This will help loosen any material adhered to the walls and thoroughly cleanse the tank for future use. 

Complete this process several times to flush any remaining waste to the front of the tank for eventual evacuation. This will keep your tank clean and odor-free. When finished, turn off the water supply, step on the flush pedal, and remove the spray gun.

Additional Trailer Maintenance Resources


Lang Specialty Trailers goal is to create innovative restroom trailers that are not only eye appealing, but are durable, easy to install, easy to clean, and functional for the professional restroom trailer operator.