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Your RV Water System Explained

(Camp Addict does NOT accept payment from any company to review or endorse their products.)

So you have an RV. You know there's some way that water runs to your sink, toilet and shower.

But how, exactly?

An RV water system can be confusing at first. 

There's a difference between using a city water connection (hose connected to your camper) and using your RV water pump to circulate H2O stored in your fresh water tank.

RV kitchen faucet running

If you aren't familiar with how an RV fresh water system works, you've come to the right place.

Here you will learn how water gets into your RV, where to find water if you are not at a campsite with a fresh water supply, and maybe even find out a thing or two about your fresh water pump.

Need to replace your water pump? Use the button below to open up the reviews and find the right type for your rig.

How To Get Running Water In Your RV

Most RVs have two options to get water coming through your RV plumbing system:

  • Attaching a hose to your RV from the outside ('city water connection')
  • Using the RV's pump to use water stored in your fresh water tank

City Water vs. Fresh Water Tank

Using City Water

One way to get water flowing through your faucets is to attach an RV water hose (different from a regular garden hose) from a spigot to the water inlet on the outside of your rig.

This is what is called using 'city water'.

With the city water method, you don't have to fill your holding tank or 'fresh water tank'. 

You also don't need to use your water pump.

With the 'city water' method, the water goes from the hose directly into and through the pipes that lead to your RV toilet, faucet(s) and RV shower head.

City water bypasses the fresh water holding tank completely.

When using city water, you can keep the outside water spigot on all the time.

RV city water hookup

Here's An Example Of An Outside Water Hose Attachment On An RV.

This way, the water pressure from the spigot pushes the water through your RV water system.

So, no need to use your built-in water pump.

Turning the water off at the spigot (outside) when you aren't home is a good option to eliminate disaster if your RV plumbing system pipes spring a leak.

Of course, using city water only works if there's a nearby spigot you can use.

If you go to an RV park and pay for 'full hook-ups', you will have a dedicated spigot to use.

When using city water, it's a VERY good idea to get a water pressure regulator to attach to your RV water hose.

Some RV parks have pressure that is too high for RV plumbing systems.

In such cases, it can bust the water pipes inside your rig, or cause leaks at plumbing fittings.

Having an RV water pressure regulator will help prevent this disaster.

Obviously, you can't use city water if you are out in the woods (boondocking) or if you are camping without water hookups.

If that's where you are going, you need to fill your freshwater tank before you get there.

Water Pressure Regulator

A water pressure regulator is essential to use when you are connected to any outside water supply.

Water pressures from town to city to town will vary.

Some have very high water pressure which can damage your existing water lines, causing a leak.

A leak will cause water damage, which is the #1 worst thing that can happen to your RV.

ALWAYS have one of these in place when connected to an external water supply.

Valterra brass water pressure regulator

Using Your RV Fresh Water Holding Tank

Pretty much any RV with a sink faucet or shower in it also has a freshwater holding tank.

This is how you get water when you are boondocking.

You may either fill your fresh water tank at home before you hit the road, or you can fill it just before you arrive at your campsite.

Also, some campgrounds will have a designated area where you can fill your fresh water tank before settling into your campsite.

If your rig is already close to its GVWR (gross vehicle weight rating), it's best to not drive with your fresh water tank full the entire way, depending on how far you have to go.

Driving with your tank full also affects your gas mileage to a certain degree, depending on the capacity of your fresh water tank.

Keep in mind that each gallon of water weighs approximately 8.3 lbs.

You do the math for your water tank (capacity in gallons x 8.3).

Of course, driving with a full fresh water tank also depends on where you can or cannot get water.

Sometimes the nearest water source is nowhere close to where you are camping.

In this case you have no choice but to fill your fresh water tank before arriving at your final destination.

To fill your tank, locate the outside potable water fill port.

Most of the time, it's pretty clearly marked.

Below is an example of what yours may look like.

Sometimes it's inside a locked compartment, sometimes it's not.

RV water fill door
RV water fill door open

If you have an older RV, just keep looking around the outside compartments until you find a hole that looks like it can fit a hose.

It's NOT the same hole that you use to stay hooked up to water as we talked about above. 

The opening for the fresh water tank fill has a totally separate entry point.

NOTE: Some RVs (mainly motorhomes) do not have a potable water fill port. Instead, they have a valve that redirects water coming in from the city water inlet to the fresh water tank.

One other way you can fill water holding tanks is with portable water containers or bladders. 

You can also fill these to help your water supply go even farther.

You then empty them into your portable water fill point (assuming your RV has one).

Doing so means you don't have to move your rig again to top-off your fresh water system.

Please note- these bags are notorious for leaking around the threaded area over time, or otherwise developing a leak, and may need to be replaced periodically. 

5 gallon water jug

Here's What Camp Addict Kelly Uses As Portable Water Containers. These Are Collapsible.

Other methods are to purchase a large bladder that you can fill at the drinking water station. 

You then utilize a free-standing water pump OR the water pump that came with your RV, to fill up your fresh water tank. 

Filling Your Water Tank Using Collapsible Water Containers

Your RV Water System Pump

You will need to turn your RV water pump on to use tank-stored  water when you are not connected to city water.

Locate the on/off switch and flip it to the 'on' position.

Bingo!

You have a pressurized fresh water system.

RV holding tank monitor panel

A Typical Tank Monitor Panel With Water Pump Switch On Left.

The pump may be in the 'on' position, but it won't necessarily be actively running. 

It's designed not to activate until the pressure in your water lines drops.

The pump is set to keep the pressure in your RV plumbing lines at a certain pressure, usually about 40 PSI (pounds per square inch).

When the pump senses that the RV water system pressure drops below that (when you open a faucet, use the toilet, or take a shower) it turns on to maintain water system pressure.

Need to replace your water pump? Use the button below to open up the reviews and find the right type for your rig.

Most RV plumbing system pumps will pulsate when water is used.

That's normal. 

So if you have water flowing for any duration, the pump will pulse on and off.

To lessen the pulsing, you can install an accumulator.

The video below is an example of a normal pump operation.

You can see that the RV plumbing system water pressure fluctuates when the faucet is being used.

If you listen closely, you can hear the pump turning on and off in the background.

Normal Water Faucet Pulsing

There are newer RV water pump models that also claim to lessen the above water system pulsation and noise.

Also, it's a good idea to keep your pump off until you need to use water.

This is just in case a leak in the water system happens.

You can avoid a big mess.

Be aware that when you first turn your pump on after filling your tank with water, the plumbing lines probably aren't filled with water yet (assuming the tank was previously run dry or had been sitting a while).

Therefore, you might hear your pump come on for a couple of seconds to prime the water system lines.

Don't be alarmed, it's perfectly normal stuff.

After a short period of time it should turn off until you use on a water fixture (faucet, shower, or toilet).

Pump Pulsing When You Aren't Using It?

When turned on, if your pump runs constantly, or pulses every few minutes and you aren't using your RV plumbing system, this is not good.

You are losing pressure which indicates you have a leak somewhere in the plumbing. 

Turn off your water system pump and start trying to locate the leak before you have water damage.

Also, your water faucet or shower might sputter and spit the first time you go to use it after filling your tank.

This is normal.

It will happen until the RV plumbing lines are completely void of air.

The water might look weird, sort of whitish.

This is again normal and is caused by the air in the plumbing system mixing with the water.

Once the air has been purged from the water system lines, you will no longer hear sputtering or see the air filled water.

You should have your own dedicated water hose for filling your rig with fresh, potable water from a reputable water supply.

Fill your rig's freshwater tank until water starts to back out of the overflow hole.

Don't forget to put the cap back on after filling the fresh water tank.

Never fill your tank using the non-potable water hose at a dump station.

People use that hose to stick down their contaminated RV sewer hose to rinse it.

Groooooooooss.

How To Find Water To Fill Your Fresh Water Tank

Unless you are filling your RV water system at a campground or from home, it can be a challenge to find water for filling your fresh water tank. 

There are a few online places that can help.

There's a website called SaniDumps that is a dump and water locator.

Also, where there's a dump station, there's USUALLY potable water as well.

There are also many dump station reviews on the website Campendium.

Kelly filling up 5 gallon potable water container

Kelly Filling Up Her Water Containers For Free At A Campground In Teton National Park.

Be Smart - Call Ahead

If you are looking at getting water from a campground but you aren't staying there, always call ahead.

Ask them if they will allow it and how much they charge.

Be aware that a lot of campgrounds in more northern regions, or at higher elevations turn off their water supply for winter. 

This is another good reason to call.

Sucks to arrive in an area only to find out that you don't have any place to fill up your fresh water tank.

Might ruin your camping trip.

Some gas stations, and the occasional camping store, have fresh or 'potable' water that you can use for free.

Potable water filing station inside store Moab

Here's A Fantastic Water Station In Gearheads In Moab. Obviously, You Can't Fill Your Camper Directly. This Is Where Portable Containers Come In Handy.

Other times you can find a campground or RV park that will let you fill.

Usually they will charge somewhere from $5 to $20, depending on how greedy they are, how large your fresh water tank is, or what part of the country you are in.

Fairgrounds are another place that often has potable water for a price.

Use the old-school 'telephone' part of your smartphone to call around.

How Does Your Water System Pump Get Power?

Your fresh water pump needs power to run. 

Where does it get power from?

It's a 12-volt device, so it uses your RV's batteries, which provide your motorhome or trailer with 12-volt (DC) power.

Even if you are connected to shore power (an outside electrical source) your pump will still only use 12-volt power.

You can learn more about the mysteries of camper power systems by reading our guide on how RV electrical systems work.

Filtering Your Fresh Water

Should you use a water filter when filling your fresh water tank?

You might think 'I don't drink the water from my faucets, so I don't need a filter'.

Well, that's only a partially correct statement.

Filtering the water that comes into your fresh water tank also filters the H2O that goes through your pump.

Filtering water before it goes into your water holding tank keeps tiny particles out of the pump.

Those unfiltered particles might otherwise damage the pump's diaphragm and eventually cause it to stop working.

You never know how good or bad the water quality is going to be during your camping trip.

It's best to use a filter whenever filling into your fresh water tank.

If your RV doesn't already come with a water filter installed (most don't), you will need to buy one that you attach to the end of your fresh water hose.

Simply attach it in between your fresh water hose and your camper and you're good to go to keep sediment from your RV water system.

Disinfecting Your Fresh Water Tank

Before you use your RV plumbing system for the first time, it's a good idea to disinfect the fresh water tank. 

Do this ESPECIALLY if you plan to use it for drinking water.

It's also good practice to do this once or twice a year to keep it nice and clean.

How To Sanitize Your Fresh Water Tank

To eliminate the bleach smell and taste after sanitizing your fresh water tank, you can add a small amount of white vinegar to the tank when you fill it to drain it a second time.

You don't have to completely fill the tank, just enough to run sufficient water through the plumbing system so you get the vinegar solution through every fixture.

Run all your faucets, hot and cold, until you smell vinegar coming out.

Let it sit for a few hours.

Then empty your fresh water tank and lines completely and refill with fresh potable water.

What About Waste Water Tanks?

So far we've only discussed the fresh water tank, but what about waste water?

Your RV plumbing system also has a black water tank and one (or more) gray water tank.

You can learn all about these waste water holding tanks by reading our RV Septic Tank Guide.

Conclusion

Your RV's fresh water system isn't that complicated.

It consists of a fresh water tank and RV plumbing to distribute water to any faucet, shower, or toilet inside your motorhome or travel trailer.

There are two options to get fresh water flowing thru the system - using the pump or being hooked up to a city water supply via a hose.

Now that you understand how to safely use your RV water system you are ready for your next camping trip!

Camp Addict Kelly
Kelly Beasley

Kelly Beasley is co-founder of Camp Addict and loves sharing her enthusiasm for the RVing lifestyle. As a full-time RVer since May 2015, Kelly's playful writing style helps make learning about the sometimes dull subject of RV products a bit more interesting.


Marshall Headshot
Marshall Wendler

Camp Addict co-founder Marshall Wendler brings his technical expertise to help explain RV products in an easy to understand fashion. Full-time RVing since April 2014, Marshall loves sharing his knowledge of the RV lifestyle.

  • New to the camping world, I have a 2004 komfort trailer. I am hooked to city water however I don’t get water without using the pump. I don’t understand why.

    • Hi Devvie,

      Unfortunately we aren’t RV mechanics so we can’t troubleshoot issues that we haven’t experienced ourselves.

      As far as I understand it (and how it works on my travel trailer), you hook a hose to your trailer’s city water inlet and as long as that hose is pressurized (has water coming through it), you have water in your rig without needing to use the pump.

      I don’t know what would be causing the city water inlet to not work.

      If you have a user manual, I’d check there. Otherwise I’d have someone familiar with this brand of trailer help you out.

      Are you able to ask the person/dealer you bought the trailer from?

  • New to RV’ing….. probably a simple question…..does my city water run thru the onboard water filter or just tank water…..our water pressure is getting bad, hose has good pressure.

    • Hi Corey,

      Without knowing how your exact RV is plumbed, I don’t know the exact answer to this. But if it’s a factory installed onboard water filter, I wouldn’t be surprised if the city water runs thru it.

      Do you have a manual with the RV that shows a plumbing diagram?

      Where is the filter located? If it’s in a utility bay, you should be able to see the water lines and may be able to answer the question by looking there.

  • We are normally hooked up, but are boondocking for the first time this year. Full timing two years.

    This time, when I run my water pump, it is pumping water out through the city water inlet.

    What causes this, and how do I stop it?

    Thanks,
    Jon

    • Hey Jon,

      Well, that’s a weird one. I don’t have any experience with that.

      I did have a water pump once where the check valve failed. This caused water to flow past the pump, into the fresh water tank, when connected to city water.

      But it’s like you have the opposite problem Very strange!

      I honestly don’t have a clue what the problem might be.

      Do you happen to have the rig’s manual? If so, it might have a schematic of the plumbing system which you can take a look at and see if it offers any clue as to what might have gone sideways. Assuming the schematic is accurate.

      Otherwise, I’d try contacting an RV mechanic and seeing if they have any ideas.

      Sorry I’m of no use here!

  • Am I correct that city water pressure will reach to the output of the 12V pump as that is a common line to both. If so, then I could connect the output of a 120V water heater, mounted inside the RV, to that 12V pump line, with city water going only to the elec water heater and the city water RV connection capped off.

    • Hey David,

      Correct, in most RVs the city water and the RV water pump share common plumbing lines to faucets, shower, toilet, water heater, etc. The pump has a backflow valve so the water doesn’t pass through it into the fresh water tank.

      I assume you are wanting to install a 120v water heater because the RV’s water heater (many have a 120-volt setting) doesn’t work?

      Why would you want to only have the city water going to the water heater? This means the cold water side wouldn’t have any water pressure from the city connection.

      Anyhow, yes I suppose it’s possible to plumb in another water heater if you have a place to install it and know how the plumbing on your particular RV ‘works’.

    • Hi Roy,

      Great question! This would depend on the pressure of the city water in the line. If it’s above the regulated pressure that the pump is set to, then the pump will not kick on. If the city water pressure is below the set pressure of the water pump, then it will kick on when needed to raise the pressure.

      In all honesty, we have never tried this, as we are boondocking 99.5% of the time. Try it and see and let us know! It won’t hurt anything.

  • We have a tiny (10′) vintage camper that only has a city water hookup currently (we only have a sink that we’re plumbing, no bathroom). I don’t know much about adding a fresh water system to it, but have considered it for when we are not at a full hook up. Is there a portable system option I could consider (portable bladder or tank with an in-line portable pump perhaps)? Or is there a good resource you could point me to about installing a system? I’m not sure where we would really have room for tanks though.

    • Hi Rachel,

      Sounds like what you want to do (no permanent tanks) is something that is done a lot on the home build van community (you know, the #vanlife ones).

      I’d take a look at what systems they put together and see if something will work for you.

      Since we don’t do the #vanlife thing, I’m not up on which sites are the best. This is where Google will be your friend.

  • Is there a way to be hooked up to city water, but set up the system to use the tank water first, and only use city water when the tank is empty? Thought about getting a pressure tank and adding a gravity fill inlet to it… would that work or would the incoming water need to be pressurized to go into a tank like that? Is there a better option I am not considering?

    • Hi Kaylee,

      Any particular reason why you would want to use the fresh water tank supply first when you are connected to city water?

      Normal RV water systems are setup to bypass the water pump (which would supply water from the fresh tank) when attached to city water.

      Am I missing a scenario where you’d want to use the fresh water tank first? Maybe I’m not completely understanding your question or what you are trying to do.

      Also not really sure what you mean by adding a pressure tank with a gravity fill inlet? I’m familiar with a ‘normal’ fresh water tank with gravity fill. And the only pressure tank I’m familiar with is an accumulator tank that is on the output side of a water pump that allows a limited amount of water flow before the pump turns on.

      Can you explain a bit more what you are looking to do so I can get a better understanding of the scenario you are looking at?

      • Hi! Thanks for your response! It’s a long story but the short version is, I want to experiment with some rainwater collection and use. So I would want collect that into a tank and use the tank first, but have the city supply on deck if there’s just not enough or the water tests are no good. I live in a cold area (zone 5) and am expecting limited precipitation collection in the winter.

        Anyway, by the pressure tanks, I was referring to the ones for use with wells, where the pump detects the pressure in the tank and if it gets below a certain set point the pump draws water up from the well. I was thinking of inserting an inlet into the tank to connect to my downspout. But that would be a passive gravity fill and I’m not sure if those tanks require a certain water pressure to fill. Then if the tank was empty, and I was calling for water, the pump could kick on and draw from the city supply? I dont love the idea because those tanks are usually on the smaller side and because I think that the city supply has enough pressure to make the pump redundant. It was just the best idea I had so far for making the city supply secondary.

        Thanks for your thoughts!

        Kaylee

        • Hey Kaylee,

          Thanks for the further explanation!

          No, RV fresh water tanks aren’t designed to be pressurized. They have a vent to the outside to facilitate venting while using the gravity fill port. Plus I’m pretty sure they just aren’t designed to be pressurized.

          I don’t think you can do an automatic fill like you are talking about. I mean, never say never, but it probably would be a total PITA to set up.

          How about shutting off the city water supply until you need it (aka, fresh water tank fill is empty). Then turning it on at that point.

          The gravity fill water ports are just that. Gravity fill. So they don’t need any specific pressure. I routinely pour water into mine (using gravity) via 6-gallon water containers.

          So you should be able to set something up where you can fill, via gravity, from a water collection cistern. I just would have some way to control the flow. Not have the water constantly running into the fresh tank as this will cause overflow via the vent.

          Hope that helps! Sounds like you are definitely trying to work the fresh water problem. I like!

  • New to game. So you fill your potable water tank (Fresh). Do you then run the pump to pressurize, or just leave it and it will turn on when needed?

    Thank You

    • Hi Kevin,

      You are correct. You fill, then you can keep your pump on all the time and it will activate when needed when working properly. If you hear it activate often when you aren’t opening any faucets, you likely have a leak.

      I turn my pump off when I am not home, just to avoid any accidents happening while I am away and can’t hear the pump running when it shouldn’t be.

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