Waste Tank Maintenance

How To Maintain Our Trailers

Starting Out

Before every event, the waste holding tank must be what’s referred to as "charged" which means the bottom of the waste tank should be covered with approx. one half inch of fresh water and treated with deodorizing packets at the rate of one or two packets per toilet. 
The Charge Scale is as follow:

Trailers Lengths
  • 8’ to 14’ = 50 Gallons
  • 14’ to 20’ = 75 Gallons
  • 20’ to 28’ = 100 gallons
This can be accomplished by the following procedure. 


  1. After trailer is set in place at the event site, leveled and blocked, open the lid of the fresh water tank located in the mechanical room and insert a garden hose.
  2. Before turning on water supply make sure all valves at the bottom of the tank are closed.
  3. Turn on water at supply and fill 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 valve then trace the water line to locate the appropriate valve going into the 3" vent stack and open that valve. The measured amount of water in the fresh water tank will drain into the waste holding tank giving you the exact amount need to charge the tank.
  6.  When the fresh water tank is empty, close the small drain valve for the pipe going into the 3" vent stack.
  7. You are now ready to drop the tank deodorizers into the toilets as described above. The waste tank is now charged and ready for use.

Pumping The Waste Tank

At the end of the rental event, the waste tank and fresh water tank must be pumped and drained prior to moving the trailer. There are just three steps necessary to accomplish this.

Not all installations are the same so there may be some differences in performing this but in general, the steps required 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.
    1. 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.
  2.  Draining the fresh water tank. At this time if there is water in the fresh water tank, open the drain valves allowing the water to drain into the 3" vertical waste tank vent stack.   
  3. Pumping or evacuating is the term for waste removal.
    1. Connect the pump vacuum hose to the Dump Valve and begin evacuating the waste.
    2. Using the tongue jack, lower the nose of the trailer as low as possible allowing the waste to run towards the front of the trailer. When finished evacuating tank, close the dump valve, remove evacuation hose, and raise the trailer to tow height.

Cleaning The Waste Tank

It is not necessary to flush the tank after every use but should be done at least once a month.

After the waste holding tank has been emptied but before disconnecting the evacuation hose, connect a hose from a fresh water source to the tank wash down gun and insert it into the toilet in the rear of the restroom by stepping on the flush pedal on the toilet to open the flush ball and carefully insert the gun into the toilet and push it all the way to the bottom of the tank and turn 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 4 walls of the tank.

Do this several time to flush any remaining waste to the front of the tank to be evacuated. This will keep your tank clean and odor free. When finished, turn off water supply, step on the flush pedal and remove the spray gun.


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.