How to Install a Dump Valve

Written by jan benschop
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How to Install a Dump Valve
Valves that work: a few bucks. Not risking a spill: priceless. (Andy Reynolds/Lifesize/Getty Images)

Dump valves are located on the left rear of an RV. They open by pulling a T-handle, and expel toilet and sink/shower waste from the vehicle. There are two sizes of dump valves: large for toilet waste ("black water") and small for lavatory and shower waste ("gray water"). The installation procedure is the same for both.

Skill level:

Things you need

  • Dump valve with nuts and bolts
  • Valve-to-pipe square flange fittings
  • Two feet of ABS pipe
  • Two ABS elbows
  • ABS adhesive
  • Wrench set
  • Phillips screwdriver
  • Silicone lube spray

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  1. 1

    Route ABS pipe to the valve location. Install it high enough to escape road scrape damage. Have a short length of pipe ready for termination downstream of the valve, and two three-inch pieces to interconnect the elbows.

  2. 2

    Clean the pipe ends and inside flange sleeves with a clean cloth soaked with alcohol. Apply ABS adhesive to the outside inch of pipe end and the inside of the flange sleeves and elbows as you install them.

  3. 3

    Slide an elbow onto the pipe end from the tank with a 90-degree twist to evenly distribute and seal the joint with the adhesive. The elbow opening should line up toward the rear of the vehicle. Use the same method to install a three-inch length of pipe, then a flange. When installed, each flange should have a flat edge of its square parallel to the pavement. Glue the other flange onto the other three-inch piece of pipe, and continue with an elbow pointing to the street. Insert another short piece of pipe into the elbow and terminate with a bayonet ring to fit the twist-on end cap.

  4. 4

    Press-fit rubber ring gaskets into the circular grooves either in the flanges or in both sides of the valve body. Spray lube on all inside parts of the valve and slide the blade back and forth a few times while reapplying the spray.

  5. 5

    Sandwich the valve body between the tank-side and street-side flanges, aligning the bolt holes. The valve handle should point toward the street. Insert all bolts through the corners of the square assembly, all pointing in the same direction. Tighten enough to compress the rubber seals.

  1. 1

    Loosen and remove all bolts on the old valve.

  2. 2

    Remove old rubber seals.

  3. 3

    Perform steps four and five in section one.

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