The 3 Types of RV Water Systems

RV plumbing is what makes this motorhome on wheels really function like a home. While traveling it allows you to be equipped with running water, a hot shower, and a toilet. Many people think of this convenience as an after thought, but how does RV plumbing work? Having a basic understanding of your RV plumbing system is important. In this article we will explain the three different types of water systems on your RV and why they are important.

Potable Water vs. Wastewater System

The first important fact to understand is that your recreational vehicle has three holding tanks. Each one has a specific and essential purpose, and it’s critical never to mix or misuse any of these holding tanks.

  1. Fresh Water Holding Tank

The fresh water holding tank provides you with running water. This water is for cooking, cleaning dishes, showering, or flushing your toilet. As you can imagine, you need to have a sizable supply of running water in your motorhome. That is why this tank will typically hold 20–100 gallons of fresh water. This is a big difference, so make sure you are realistic in what size tank you will need.

Most RVs will have two different fresh water inlet connections. This secondary inlet is for a pressurized city water source connection. If you’re camping at a campground that has water hook ups, they will usually provide hoses and connections for your fresh water holding tank.

Pro Tip: Camp site water is not always desirable. Consider buying a water filter. These small devices can eliminate sediment, microorganisms & bad odor from the water.

  1. Gray Water Holding Tank

Gray water is wastewater that does not contain toilet sewage. This will be the drainage from your sink, appliances, and shower. Although gray water is not as contaminated or dangerous as black water, it should still be disposed of safely. Both gray water and black water should be discharged into the municipal sewer system, but under certain circumstances your grey water can be disposed of outdoors.

If you do dispose of your grey water outside then you need to follow a few safety protocols. To start, you must be a safe distance away from surface water, such as lakes, rivers, and streams and on porous ground that can absorb it. Make sure all of your soaps and detergents are environmentally safe, so it will not do any damage.

3. Black Water Holding Tank

Your toilet is the only interior fixture that drains into the black water storage tank which is also called the septic tank. This separate tank requires more thorough cleaning, and can only be disposed of in the sewer system.

Pro Tip: Consider purchasing a macerator pump to make disposal of your black waste easier.


While you should leave plumbing to the pros, it is a good idea to understand plumbing basics when you’re out on the road. TNT RV can help you with all of your plumbing and maintenance needs. Contact us to make sure your motorhome is road ready before your next adventure.