DIY Sailboat Holding Tank

Written by sally brooks
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DIY Sailboat Holding Tank
Installing a holding tank alleviates the need to deal with sewage during a boating trip. (Jupiterimages/ Images)

The Clean Water Act requires a sailboat fitted with an installed toilet operating in U.S. waters to have a marine sanitation device (MSD). An MSD prevents a marine vessel from dumping untreated sewage into a body of water. One of the three types of MSDs allowed by the U.S. Coast Guard is a holding tank, which stores sewage until it can be legally disposed of. Installing a holding tank on your sailboat can be accomplished in just a few steps.

Skill level:
Moderately Easy

Things you need

  • Polythene holding tank
  • Marine tie-down strap kit
  • Flathead screwdriver
  • Plastic sanitation tubing
  • Plastic sanitation fittings
  • Adjustable wrench

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  1. 1

    Choose a level spot on the sailboat near the waste outlet that can support the weight of a full holding tank. Ensure the area where the holding tank will be secured is equipped with marine plywood or wood, not fibreglass, to avoid damage to the boat.

  2. 2

    Clean the area and position the holding tank so that it will be easy to connect the tank with the waste outlet of the toilet.

  3. 3

    Use the tie-down straps to fix the holding tank into place. Using a flathead screwdriver, secure the straps with marine-grade plastic screws.

  4. 4

    Disconnect the tube connecting the toilet and waste outlet. With a wrench, use new sanitation tube fittings to attach a new sanitation tube to the toilet and the port on the holding tank. Do not over-tighten the fittings, as this may cause damage to the connection points.

  5. 5

    Install the vent line following the tank manufacturer's instructions, making sure the vent fitting is a minimum of 24 inches from an opening into the interior of the sailboat.

  6. 6

    Test the tank for leakage by flushing the toilet and checking the connection points for condensation.

Tips and warnings

  • Choose the size of your holding tank based on the length of trips and number of passengers. Ensure the wall thickness of the tank will support the maximum weight of waste for the size of the tank. For instance, .375 inches is the minimum thickness for a 30-gallon tank.

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