There usually are three types of holding tanks in RVs. One is for portable fresh water, one for gray water and a third for black water. Gray water is waste water from the sink and shower, and the black water is for the waste from the toilet. When choosing a fresh-water plumbing system, you have two choices: one that bypasses the fresh-water tank and water pump with a spout, and a hose that connects near your utility area. When planning your plumbing, a holding tank should be considered because it allows you to travel long distances without having to empty. The type of system you choose should be based on your needs.
Select your holding tank after careful consideration. Think about how far you want to be able to travel and how much space you are willing to sacrifice for the tank.
Sketch on paper the outline of your RV to decide where you want to mount the tanks. Think about where the plumbing is because you want your tank to be close. In your drawing, mark the location of the toilet, sinks and shower for reference.
Draw in the holding tank. You want the toilet over the black tank. This will make flushing easier. The gray tank should be between the shower, the sinks and the fresh-water tank. This should be located somewhere in the middle of the unit, so it can be hooked up easily to the plumbing.
Mount the water pump per instructions. It should be located between the fresh-water plumbing and its holding tank.
Mount the tank per manufacturer's instructions. This will vary from unit to unit.
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