How to Prime an RV Water Pump? – 5 Simple Steps

how to prime an rv water pump

RV living is fun, yet can also be demanding. Proper maintenance is crucial, and among others, you should not forget your 12-volt water pump—a component responsible for distributing water throughout your motorhome.

To ensure the full functionality of your pump, priming is one of the most important tasks. This is done after long-term storage, winterizing, or cleaning. Priming will build pressure to draw water and bring it where needed.

If you’re clueless about how to prime an RV water pump, this is the right place. Keep on reading as we talk about the basic steps. With the right knowledge, you can easily optimize your RV’s water system.

A Step-by-step Guide to Prime an RV Water Pump


If you have a pump not working when winterizing or not building pressure, priming can be an effective solution. To start, gather the necessary materials:

  • Flathead screwdriver
  • Bucket of water
  • Tube/hose

1. Disconnect the pump


The first thing to do is disconnect the pump from the city line or the water tank.

  • Look for the water pump in your RV—it’s usually located near the tank. The specific appearance can vary, but in most cases, your pump will look like something in the photo below.
  • Use a flathead screwdriver to turn the pump’s collar and/or clamp screw counterclockwise.
  • Disconnect the hose and let it drain out the remaining water.

2. Fill the tank with water


Before you prime water pump in RV, make sure that the tank has enough water. If the RV has a gauge, check it to be sure of the water level. This task is easy, although the specific directions can vary across different models.

With the tank now open, insert a clean plastic tube or hose. Hold the top part and slowly pour water from a bucket. Never put a dirty tube/hose in the tank, as you’ll introduce bacteria into the water system, which can be a health hazard once you’re done priming.

3. Open a faucet


After filling the tank with water, open any faucet, such as the one in the bathroom or kitchen sink. Doing this will let air pass through by releasing pressure.

4. Turn the pump on


Locate the on/off button and turn it on. If you can’t find the switch, consult your manual.

As soon as you power the pump, it will initiate priming. This is done by drawing fresh water out of the tap, pushing it to the pump, and eventually flowing through the faucet.

Keep the pump running for one minute. You’ll know that the pump is working properly when air is spitting out of the faucet, although you’ll have to wait a few seconds for this to happen.

5. Allow the water to flow from the faucets


As the pump runs, see to it that the faucets are on. Do this until there’s no more air in the water line. Run all the taps to purge air buildup and let water flow unhindered. At this point, you should be done priming.

Once done, reconnect all the water lines.

Frequently Asked Questions

Why doesn’t the RV water tank prime?

If your RV water pump won’t prime, something could be blocking the pipe. A faulty electrical connection can also be the culprit. You might also want to check for potential leaks.

Frequent inspection is one of the most important to diagnose and address any problem early on. Regular sanitation is also important, which will ensure a clean water supply in your motorhome. Maintaining the filter is also a must. Lastly, don’t let the pump run dry.

Why is my RV water pump humming but not pumping?

A humming or running but not pumping tank is likely because the tank is dry. It may not have enough water to move. This can damage the motor, so make sure to avoid such.


As noted in this short guide on how to prime an RV water pump, the process is straightforward. Start by disconnecting the tank from the water supply and filling it with water. Run all the faucets and let air pass through the system to prime the motor.

If your RV water pump fails to run, although you’ve done everything correctly, there’s a chance that this component has become defective. In this case, a replacement is necessary.

5/5 - (2 votes)