How Does Your RV Water System Work? Answered!

How Does Your RV Water System Work Answered!

Understanding how your RV water system works is good to keep your RV in top condition, allow you to do minor repairs, or help explain any technical problem to your RV plumber. The RV plumbing system starts with freshwater coming either from treated municipal/city water or the campground water source (well, lake, spring, etc.).

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It can enter directly either into your RV freshwater plumbing or your freshwater tank (which will use the water pump to distribute the water (either via hoses/pipes) to your kitchen and RV bathroom). Wastewater from the kitchen and shower then gets stored in the grey water tank, while toilet waste goes into the black tank – up until it gets emptied at a dumping station. We’ll discuss the different components and related accessories in the next section to help you understand it more.

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RV Water System Components

RV water systems are similar from model to model, but each component may be located differently based on your RV’s make, model & floor plan. Let’s start at the beginning of the water source:

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Water Pressure Regulator. A water pressure regulator controls the water pressure before it enters your RV. It isn’t part of the default RV water system, but it is an integral component to protect the plumbing system, especially if you connect to a pressurized “city” water hookup. I write more about it in detail HERE.

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Water filters. These remove water impurities (particles, chemicals, microbes) using either a physical barrier, chemical, or biological processes. Although also not a default part of the RV water system, having a water filter will prove to be very important.

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Chemicals used for ‘city/municipal’ water may or may not be too noticeable, but when it comes to different campgrounds they can use unprocessed water sources: lakes, wells, springs that may come with sediments, minerals, chemicals, or microorganisms that also may give the water a certain color, smell or taste that can make it unpleasant to shower with or drink. This is why, to be safe, you can have an in-line RV water filter and/or a designated drinking water filter system.

Freshwater hose. Designed to meet drinking water safety standards, this hose can come in different colors (often white so it doesn’t get mixed with other hoses), and can range from USD$16USD$ 32, depending on the length, thickness &/or other features (e.g., anti-kink or weight) when connecting your RV to a water hookup. Using a garden hose isn’t recommended since it may leach chemicals into the water, as they get exposed to heat &/or age, as discussed in the article HERE.

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Water inlets. There are two water entry points into your RV, one for the “city/municipal water” inlet (via the spigot hookup), bypassing the freshwater tank since pressurized water can circulate through the RV plumbing system on its own.

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The second water inlet goes straight into the fresh water tank (which requires a pump to circulate the water through the system). Most RVs have a switch inside the trailer/coach (to choose between turning the water pump on or using city/municipal water).

Water Tanks. All RVs have three tanks and come in different sizes:

  1. Freshwater. This tank is only for clean water and often made of HDPV plastic (which means it has a low risk for leaching chemicals). Its location depends on the RV layout, usually inside the cabin (under a bench or bed). In Class A motorhomes, it can be located under the floor with an external basement access door.
  2. Grey. This tank is where wastewater from the kitchen/bathroom sink and shower go. It’s often found on the driver’s side, at the back of the motorhome/trailer. It will have a hose vent that goes to the roof for any gas to exit.
  3. Black. This tank only holds toilet waste, is located by the grey tank and also has a vent that releases any gas build-up. Make sure to always keep the release valve of this tank closed unless dumping the contents, so that any solid waste doesn’t settle and harden (which can make it difficult to clean and later cause a lot of problems for your toilet).
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Water pump. The pump is typically found near the fresh water tank so it can circulate the water inside your RV. Depending on the type, the flow rate can be adjusted between 3-6 gallons per minute (GPM). Adjusting the water flow is good so you get enough water, without using it up too fast.

On average, you’ll want your RV sink to have a flow rate of 1gpm and showerheads at 1.5-3gpm. Older RVs can handle water pressure between 50-60 pounds per square inch (PSI), while some newer RV plumbing systems can handle up to 100psi. Remember that the water pump isn’t used if connected to city/municipal water.

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Water heater/boiler. Depending on the type, the average RV water heater holds 6 – 10gallons of water. typical water heaters run at 8,000 to 12,000 BTUs. It takes about half an hour to heat up the hot water.

Many New RVs now also have on-demand hot water systems which operate at 20,000 to 60,000 BTUs. There’s also a water bypass system next to the water heater or instant hot water system for winterization of your unit.

Plumbing pipes and fixtures. Similar to house plumbing fixtures, ideally having low-flow aerator types for your RV will help reduce water consumption:

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RV Toilet. RV toilets are different from regular house toilets since water doesn’t directly fill up the bowl to create a water seal (to prevent smell since the toilet is directly connected to the black tank). A small lever/footpad has to be pressed/stepped-on to fill the toilet bowl before using.

Some water-saving RV toilets can consume just one pint (0.47L) of water to flush. Other RV toilets have a bidet (hand-operated spray nozzle/“bum gun”) which can be used to clean the toilet before flushing. In case you’re keen on using the latest water-free or compost toilets, there is also a lot to choose from.

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Dump Valve. The black and grey tanks converge into one dumping valve to empty the tanks at the same time. I write a detailed guide on how to clear the grey and black tanks HERE.

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Dump Hoses, hose supports, connectors/adapters, and seal (also known as a “doughnut”). Because these accessories may (or may not) come with your RV, it pays to have an extra set of dedicated accessories, especially if the dump area is inconveniently located too far from where your RV is parked. They can come in kits and have extensions, hose supports, and clean out hoses to flush out the tanks as needed.

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How Much Water Do I Use In A Day In My RV?

The water you need/day depends on how many are camping and your camping lifestyle:

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  1. Boondocking:

If boondocking, you need to compute how much water you need per person (+pets), per day, based on your camping lifestyle (drinking, cooking, cleaning/laundry). You’ll need at least 2L of drinking water/person/day to avoid dehydration in temperate climates (more in hot and humid climates). As a guide, below is the average amount of water used:









*military-style shower (tap on: get wet, tap off: soap, tap on quick rinse, tap off)

A couple can frugally consume ~23L (6gallons)/day of water (combined). With the consumption averages in mind, multiply the amount/day by the number of days you’re boondocking. Usually having a 230L fresh water tank is enough for 7-10 days.

  • Campsite with full hookups:

You get an unlimited water supply when fully hooked to a campsite, so your consumption will be similar to being at home. You don’t have to worry about conserving water, but will just be constrained by the size of the grey water tank. Dumping waste tanks typically happens every 1-2 days.

  • Campsite with Partial (water & electricity) hookups

Partial water hookups lessen the burden of conserving water, so refilling the fresh water tank can be every 2-4 days (depending on your consumption). The only constrain will also be how often you need to dump wastewater.

Can I Drink Water From My RV?

It’s safe to drink water from your fresh water tank, provided you use a drinking water hose, the water has been properly filtered, and properly stored in a sanitized tank. The water tank should be sanitized at least once at the start of the camping season or every 3-6 months.

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Bringing water jug(s) from home or a grocery store is another option to avoid any off-putting taste from the tank if it wasn’t properly cleaned (from the winterization antifreeze or any other possible contamination). If you’re keen on having clean drinking water, installing an additional under-sink water filter can range from USD$59.99USD$199++, depending on the kind of filtration you’ll need.

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How Often Should I Sanitize My RV Water System?

Sanitizing the whole RV water system regularly is simple and good to practice, especially if using it for drinking water. Sanitize it:

  1. Before the start of camping season, after de-winterizing.
  2. If you placed non-potable water in your freshwater tank, or hooked up to a questionable water source.
  3. Every 3 to 6 months (if living in your RV long-term)
  4. If moving between different campsites/locations throughout the year.

How Do I Sanitize My RV Water System?

To clean your RV water system:

  1. Make a bleach solution:













  1. Put the solution in your freshwater tank, then fill the tank with water using the drinking water hose and an in-line filter.
  2. Run each tap (and your shower) one at a time until you smell the bleach, and until the tank is empty.
  3. Fill the tank with fresh water and leave it overnight
  4. Repeatedly do step 3 until the bleach smell disappears.
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How Long Can You Keep Fresh Water In Your RV?

Freshwater can technically be stored forever without going bad – as long as there are no contaminants. Filtered water can get contaminated if bacteria, mold, or fungi grow (with the right breeding conditions). If in doubt, boil drinking water (for at least 15 minutes) to kill any microorganism.

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Remember that boiling water won’t remove sediments, chemicals, or minerals that can influence the water’s taste. Using HDPE (high-density polyethylene) containers (for your freshwater tank, water jugs, food containers) would be ideal so it also doesn’t leach chemicals.

How Do I Know When My RV Water Tanks Are Full?

All RVs have a water-level monitor inside the cabin to see the water level for each tank at any point. With an LED light, it usually indicates if it’s at 1/3, 2/3, or full. Many new rigs also come with a freshwater monitor at the water inlet (on the outside of the RV, under the basement door), and you can also visually see the freshwater tank manually.

[photo of cabin water-level monitor & another photo of the water-level monitor near the door]


Hopefully, this article can help with some of the most important things you need to know about your RV water system. Not only will these tips keep your drinking water supply safe, but also keep you worry-free during your camping trip.

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