How to Prime an RV Water Pump

how to prime an Rv water pump

Every camping enthusiast knows that having a constant water supply is vital. And one of the most important amenities in an RV is running water. The RV water system also runs on a 12-volt water pump that distributes water through it.

A proper water supply depends on a working water pump. If you have your RV water pump for longer periods, it might not work due to lost pressure. Therefore, learning to prime a water pump is essential for any RV owner.

Priming the RV water pump means pressurizing the pump system to get it working again on its own. You’ll have to manually prime the water pump by flushing the RV water pump and forcing water through it to restore the pump’s pressure. Read more to learn how to prime your RV water pump, plus answer a few commonly-asked questions.

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Priming an RV water pump

The process of priming an RV water pump is pretty straightforward. But the hard part is finding the RV water pump. Follow the guide below to prime a 12V water pump properly.

Things you’ll need

  • Flathead screwdriver
  • Rubber hose( same size as the main water outlet line)
  • Water
  • A jar that can hold more than 12 ounces of water


  • Fill up your freshwater tank.
  • Go through your RV manual and locate the tank and pump. If you do not have your RV manual, search for the water pump near the water tank and its main waterline. Then trace the waterline until you reach the pump. You’re likely to find the water pump under the cabinets, bench seat, or kitchen sink.
  • Locate the outlet that connects the main water line to the pump, then disconnect the water outlet from the pump.
  • Use the flathead screwdriver to loosen the clamp screw by turning it counter-clockwise. When it is loose enough, pull the hose away from the pump.
  • Remove the hose collar from the main outlet line and fix it to the rubber hose.
  • Then attach that rubber hose to the water pump and secure the screws on the clamp.
  • Pour about 12 ounces of water into the jar, then hold the rubber hose, in the air, at a higher level than the water pump.
  • Now pour the water from the jar into the rubber hose that connects to the water pump.
  • Cover the hose’s opening with your thumb and turn on the water pump.
  • Pressure will start building up inside the pump, and you’ll feel it pressing against your thumb. Do not take out your thumb.
  • Wait for one minute, then turn off the water pump.
  • Disconnect the rubber hose from the water pump, then use the screwdriver to reattach the outlet water line to the RV water pump.
  • Turn on any of your faucets in your RV  and turn on the water pump. The water will spit out of the faucet then start flowing smoothly after about two minutes.
  • Let the water run for several minutes to dispel any antifreeze residue or debris that could be in the waterline.
  • Turn on all the faucets one at a time to purge out air buildup to help the water flow out smoothly.

Does an RV water pump need to be primed?

The RV water pump needs priming when it remains unused for a while. This is because the pump loses pressure when it stays off for a long duration, yet it needs pressure to spurt out water from the tank to the water lines. So whether you’re from winterizing your RV, regular maintenance work, repairs, or installing a new water pump, priming the pump is necessary for it to work efficiently.

Priming involves flushing back the pump and forcing water through it. Doing so creates enough jetting pressure to ‘resuscitate’ the pump.

Priming also reduces the risk of pump damage during start-up. In addition, it maintains the pump’s functionality because the water acts as a coolant, preventing the pump from overheating and eventually damaging other critical pump components.

The only time priming a water pump is unnecessary is if the pump’s suction port is lower than the water tank level as the pump is already filled with water and is therefore primed.

How do you get the air out of an RV water pump?

Air in the water system can impact the water pressure and prevent water from flowing through the water tanks. Follow the simple steps below to bleed your RV water pump without special tools and expertise.

Method one

  • Open the furthest faucet away from the water pump.
  • Let the water flow through and then open the faucet furthest from the water pump.
  • Wait for the air to come out. The water will sputter and then come out as a steady stream when all the air comes out of the pump.
  • If this procedure doesn’t work, use the more effective method below.

Method two

  • Locate your RV water pump and then disconnect the water output pipe.
  • Attach a long enough rubber hose in the place of the water output pipe.
  • Fill a 12-ounce container with clean water.
  • Hold the open end of the rubber hose higher than the water pump and pour the water into the water pump.
  • Cover the free end of the rubber hose with your thumb tightly, and then turn on the RV water pump. After a few minutes, you will feel the water hit your thumb, but do not remove it. The water will circulate in the RV water pump and remove the air from the unit. Once you feel that, turn off the pump.
  • Disconnect the rubber hose from the pump and reconnect the water outlet pipe.

How long does it take to prime an RV water pump?

Priming your RV water pump should take you less than an hour. The hardest part of this process may be locating the water pump in your RV and will probably take the longest time to access it. Once your pour water through the rubber hose and into your water pump, give it about a minute for the pressure to build up. Once you feel the water touch your thumb, the pump is well-primed, and you can turn it off.

Signs that your RV water pump isn’t primed

Other than knowing how to prime your RV water pump, you need to know when to prime an RV water pump is necessary. Here are signs that indicate your RV water pump requires priming.

  • There is no water coming out of your faucet.
  • Water is sputtering out of your faucet.
  • The pump is running, but no water is coming out of the faucet.
  • The taste of antifreeze from your kitchen faucet. Priming also removes antifreeze from your water lines after winterizing your RV.
  • Low pressure on the gauge.

Why is My RV water pump not working?

The water pump is the hub of your RV’s water system. Without a working water pump, you will not enjoy the convenience of running water in your RV. Below are all the possible reasons why your RV water pump is not working.

No water in the fresh tank

The pump will pump air instead of water if you have an empty water tank. Sometimes the water tank may display full reading, but you have to cross-check if it is full or not.

Broken pipeline

Check for a break in the incoming and outgoing pipes from the water pump or loose connections. This breakage could leak water and prevent it from flowing to the rest of the lines.

Air in the pump

Check if there is any water passing between the line that connects the fresh water tank and the water pump by opening the pipe with a wrench. If there is no water, it means the pump has sucked in air, and you have to bleed it out.

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Electrical issue

Problems with any electrical component in your water pump can prevent the motor from running. Some of the reasons include; valve issues, ruptured diaphragm, or worn impeller. You will have to consult with a pump technician to fix the issue.


A well-primed water pump ensures water flows steadily from the tank to the faucets, shower, and water hoses. By following our instructions, priming and bleeding the water pump after repairs or winterization should no longer bother.