How to Prime RV Water Pump

How to Prime Your RV Water Pump in 5 Steps

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Have you ever been out camping in your RV only to discover that the water pump isn’t working? It’s enough to turn the perfect adventure into a horrible disaster.

For many RV owners, being able to turn on a faucet or showerhead to find clean water is one of the joys of RVing. Yet, few people know what to do when their pump needs some troubleshooting. Whether your water pump is still new or it hasn’t been used in a while, the first thing you have to do is to prime it.

So how do you prime your RV water pump? We’re here to show you how and discuss a few other pump-related stuff.

Let’s get started!

What’s the Function of a Water Pump?

Anyone who’s done any type of camping knows how important it is to have fresh running water. That’s why the water pump installed in your RV is absolutely crucial.

An RV water pump draws the water from the tank up through the pipes. It’s responsible for delivering a certain amount of water every minute. The quantity being dispensed through the pump is measured in proportion to the size of the RV.

How Does a Water Pump Work?

The water pump in your RV works via the vehicle’s 12-volt battery. The two main parts of a water pump are the motor and the pressure switch.

When you flush the toilet or turn on your faucet, the pressure switch senses a drop in the water pressure. This signals the pump to work and up the pressure again.

For your pump to operate properly, you need to turn it on. Some pumps can be left on even when you’re not using any water. Then, there are other types of pumps that should be turned off when there’s no water demand. This helps prevent any damage happening to the motor or any of the other parts.

You also need to have an adequate supply of freshwater in your RV water tank. You can use a tank gauge to achieve this in the most convenient way.

Water Flow Rate

The water flow rate is measured in gallons per minute (GPM): That’s how many gallons a pump can deliver in one minute. Moderate-sized RVs have pumps that can deliver around 3 gallons per minute. Larger RVs require a pump that can supply no less than 5 gallons per minute.

Two factors determine the needed rate of water flow. First, there’s how much water you consume. Then, there’s the actual size of your RV’s holding tank.

You also have to consider the maximum water pressure your plumbing system can withstand. While most modern RVs can handle up to 100 pounds per square inch (psi), it’s recommended that you never let it go over 60 psi to keep the plumbing system in good shape.

The best way to measure your vehicle’s water pressure is to opt for a water pressure regulator.

Types of Water Pumps

Standard water pumps work via two voltages: 12-volt and 24-volt. Almost all RV water pumps run on 12-volt batteries.

24-volt water pumps are believed to offer higher amounts of water pressure. But 12-volt pumps are better equipped to handle an RV’s plumbing system.

For one, it’s safer on the RV’s electrical grid. Plus, it doesn’t cause fluctuations in your water and power consumption.

Important Safety Tips

Pay attention to these safety tips when priming your water pump. They’ll ensure that the process goes effortlessly and hassle-free.

Use a Clean Hose

The whole point of having running water is to either drink it, use it for cooking, or take a shower. That’s why it’s vital to use a clean hose during the priming process.

It’s better if you get a brand new one. But if you can’t, at least make sure it was used for drinking water. That way, you can ensure the water reaching your RV is also 100% clean.

Get Rid of Trapped Air

If your water lines have trapped air, you’ll have a higher likelihood of pressure build-up. That’s the last thing you want to happen to your RV. It could cause serious damage to the pump and the water lines. Pressure build-up could even lead to a failure of the entire plumbing system.

To remove trapped air, pour one gallon of water into the water lines. The water will push out all the air and reduce any chance of pressure building up in your pump.

Fill the Water Tank

Make sure you take a look at your tank to check the water levels. This has to be done before you embark on your RV adventure. It also has to be done before priming the water pump.

Remove Antifreeze

If you’re unfamiliar, you probably pour antifreeze in your pipes when winterizing your RV. It prevents your pipes from freezing during extreme temperatures.

If pipes freeze, they can crack or break, or, worse yet, burst from the pressure. This means you have to install brand new pipes. You may even need to replace other plumbing components, depending on what was damaged the most.

When it’s time to take your RV out of storage, the first thing you have to do is prime the pump. Once you’ve done that, the next step is to keep the faucet running until the water is completely clear.

This should take anywhere from 5 to 10 minutes. It’s the best way to ensure there’s no more antifreeze left inside your pipes.

How to Prime Your RV Water Pump in 5 Easy Steps

Priming the water pump means to create enough pressure through the pump. This pressure forces it to start pumping water into your RV once again.

The actual process of priming your pump is quite basic and straightforward. The hard part is getting to the pump itself because it’s usually located in spots that aren’t easily accessible.

The easiest way is to look at your RV manual. It’ll provide information on where the tank and pump are located.

If that’s not an option, look near the water tank; pumps are almost always located somewhere near the tank. Find the water tank and its main waterline. Then, trace it all the way back until you reach the pump. Generally speaking, you should find the pump under the cabinets, bench seat, or kitchen sink.

If all else fails, take it to a professional. Priming the water pump is extremely important, and you should do all it takes to get it done.

If you’re up to doing it yourself, here are a few basic tools to help you during the process.

Now, it’s time to get started on the priming process. Follow these instructions to prime your RV water pump quickly and efficiently.

Step 1: Disconnect the Water Outlet from the Water Pump

The first step is to disconnect the water outlet from the pump. This outlet is what connects the main water line to the pump and allows water to flow into your RV.

Using a flathead screwdriver, turn the clamp’s screw in a counter-clockwise direction. Once the screw is loose enough, you can pull the hose away from the pump. Since it may drain some leftover water, you should keep your distance.

Step 2: Remove the Hose Collar From the Outlet Line

Take off the collar from the main outlet line and attach it to the rubber hose. Next, attach that hose to the water pump.

Before screwing down the clamp, make sure both the hose and the waterline are the same size. It’s also a good idea to have the hose long enough to extend out from the area where the water pump is located. If you pick a short hose, you may be forced into uncomfortable positions.

Step 3: Pour Water Into the Connected Rubber Hose

First, pour about 12 ounces of water into a clear jar. Next, hold the rubber hose at a level higher than the water pump. Now pour the water directly into the rubber hose that feeds the pump.

Step 4: Turn on the Pump for One Minute

As soon as you pour all the water into the hose, cover the hose’s opening with your thumb. Then, turn on the pump.

As the pressure builds inside the pump, you’ll quickly start to feel the water pressing against your thumb. Don’t take your thumb off the opening no matter what.

Wait for a full minute before turning off the RV water pump.

Step 5: Reconnect the Waterline

With the pump turned off, disconnect the hose from the pump by opening up the clamp. Next, use the flathead screwdriver to reattach the outlet water line to the pump.

Afterward, open any of your faucets and turn on the water pump. The water should start flowing after a couple of seconds.

Leave it running for a minute or so. This is to ensure that the waterline and the pipes have no remaining antifreeze or any type of debris.

After making sure all the faucets have clean, running water, you can pat yourself on the back. You’ve successfully primed your water pump!


These are some of the frequently asked questions from fellow RV owners.

Q: Can I leave the water pump turned on in my RV?

A: Yes, you can leave it on as long as you’re not connected to any external water line. If it’s working properly, it won’t use any power when you’re not using water.

Q: What do I do if the pump keeps turning on and off with the faucets turned off?

A: Water pumps have built-in pressure switches. When you open your faucet, the pressure drops in the pipes, which signals the pressure switch to turn on the pump. Once the required pressure is reached, the pressure switch will automatically turn off the pump.

When the pump is constantly running even with zero open faucets, that could mean any of the following:

  • A loose connection
  • A crack in one of the water lines
  • A leak in the water system
  • A faulty pressure switch

Q: Why is there no water in any of the faucets even though the pump is working?

A: Start by checking the freshwater tank gauge. If the water level has dropped, it could be the reason why water isn’t reaching your faucets or showerhead.

Another thing to check is the water lines running from the pump to your RV. Make sure they have no cracks, loose connections, or worn areas.

Finally, see if there’s actual water flowing into the pump. Carefully disconnect the waterline running from the tank to the pump. If there’s water, then everything there is running smoothly.

However, if the waterline seems to be dry, it could be that something is clogging it. It could also mean it’s been damaged and needs to be replaced.

If you’ve checked everything and there’s still no running water in your RV, then it’s time to check the pump itself. You may need to replace the pump motor or pressure switch. Or you could simply install a new pump.

Q: Can I overfill the water tank?

A: No. The main problem with overfilling the tank is the extra weight you’ll add to your RV. Each one gallon of water weighs about eight pounds. So, a 50-pound tank can add a whopping 400 pounds to your RV!

The Takeaway

Owning an RV has many perks; one of them is having running water. Nothing beats the feeling of stepping into the shower after a fun-packed day spent exploring the wilderness.

There might be one thing that beats it, and that’s flushing the toilet. That’s why it’s important to learn how to prime your RV water pump.

A well-primed water pump will make RV camping more enjoyable and less stressful. It’s a simple process that can mean the difference between having clean running water and having no water at all!

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