How to Prime an RV Water Pump (5 Simple Steps)

If you’ve recently replaced your RV water pump or just pulled your camper out of storage, you’ll likely have to prime the pump to get the system pressurized and working again.

Luckily, this can be done in a few simple steps!

So, let’s learn how to prime your RV water pump the right way, plus cover some troubleshooting tips if your water pump still doesn’t pump water.

How to Prime an RV Water Pump 

To prime a 12v RV water pump, you’ll need to fill up your freshwater tank, turn on the cold water tap, flip the water pump switch on, and allow the pump to prime by moving water from the tank, through the pump, and out your faucet. 

Of course, this is a high-level overview of the priming process. Let’s break down each step and provide a few tips to make the process go as smoothly as possible.

Important: Before beginning, check your RV or travel trailers manual for details on priming your water pump. It may contain specific instructions on how to manually prime the pump depending on the year and model.

Step 1: Fill the Freshwater Tank

Begin by filling your freshwater tank with water. Check the gauge (if you have one) to ensure it’s full.

Now is also a good time to ensure all the valves are in the proper position. For example, the winterization valve is closed, the fill tank valve is in the normal position, etc.

Step 2: Turn on Cold Water Valve

Next, turn on one cold water tap, for example, your kitchen faucet. Ensure all other taps in the camper are turned off.

Step 3: Turn On the Water Pump

It’s now time to turn on the water pump. The on/off switch is typically located on the monitor panel. However, you may need to consult your recreational vehicles owner manual if you can’t locate it.

When you turn your pump on, it will “prime” itself by pulling water out of the freshwater tank, through the pump, and eventually pushing it out the tap.

Step 4: Let Pump Run

If your pump is operating correctly, you should notice air spitting out of the faucet tap when you turn the pump on.

Keep in mind it can take a while for the water to make its way through the water lines and out the faucet tap.

Once the water starts coming out of the tap, let it flow until all of the air is completely out of the line, and shut it off.

Step 5: Repeat With All Water Taps

Lastly, we need to purge the air out of every water line in the RV. So, open every faucet one at a time and allow the air buildup to be purged and the water to flow smoothly.

Your pump should now be primed and the water system pressurized. Your pump should only turn on at this point when a faucet is on.

Important: If your water heater was in by-pass mode while priming and pressurizing your plumbing system, be sure to flip the by-pass valve to allow the hot water heater tank to fill up before turning it on.

RV Water Pump Troubleshooting Tips

Figure 1: Shurflo 4008 Series diaphragm pump troubleshooting tips from the owner’s manual.

If your RV water pump is still not pumping water, there are a few things we can check to get it working again.

Related: RV Water Pump Keeps Running? Do This!

  1. Check the freshwater tank: Let’s start with the most obvious – is the freshwater tank full? Be sure to check the tank gauge. We won’t hold it against you if you forgot to fill the tank or accidentally put the water hose in the wrong inlet (like the black tank flush inlet. Yes, it happens).
  2. Check the water lines: Inspect all the lines connected to the water pump, starting with the line to the pump itself. Look for loose connections, damaged lines, or signs of leakage. Then, double-check the lines leading to all of the faucets in your rig.
  3. Check the valves: While you’re inspecting the lines, check that all of the valves are in the correct position, including any winterization valves, intake valves, etc.
  4. Check the 12v water pump fuse: If you don’t hear the pump making noise it could possibly be a blown pump fuse. Check the fuse, change it if needed, and try switching on the pump again.
  5. Check the inlet strainer: Make sure the pump inlet strainer is clean (and check the lines for kinks while you’re at it). The typical pump strainer is a fine mesh that can quickly clog if the water in the freshwater tank ever had any sediment in it.
  6. Manually prime the pump: Most RV water pumps are self-priming. They ship with a little bit of water in them to help them prime. However, after sitting in storage for an extended period of time or if you blew out your lines, you may need to manually prime them. Every model is different, but on Shurflow water pumps, for example, you can remove the strainer, pour a little bit of water in it, run the pump for a second, pour a little more water in, then replace the strainer. You can see the process in action in the video below.
  7. Check the pump: Lastly, the pump itself could be bad or it’s not getting the correct voltage.
Water Pump Troubleshoot

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