What Is an RV Water Pump and How Does It Work?

Posted by
John Woodard on August 04, 2023

Drinking, washing your hands, and showering with running water while off the grid are some of the benefits of owning an RV. To enjoy your RV experience, water must be able to make its way from point A, your fresh water tank, to point B, the fixture you are using. An RV water pump serves as the delivery service between these two points. While you may not notice an RV water pump while it is working, a faulty pump can be the difference between an enjoyable camping experience and a miserable one. In this guide, you can learn more about what RV water pumps are, how they work, and how to troubleshoot and maintain them.

What is an RV water pump?

An RV water pump delivers water from an RV’s fresh water tank to the faucets, toilet, and shower. Without a working water pump, an RV’s plumbing system is not functional. RV water pumps come in many configurations to best suit the needs of individual RVs. For example, a large RV will need a more powerful pump than a Class B RV. RV pumps also come in multiple output rates, 3.5 GPM and 5.0 GPM being the most common. When connected to city water, the RV pump is bypassed because city water is already pressurized.

How does an RV water pump work?

An RV water pump is a motorized diaphragm pump that delivers water from an RV’s fresh water tank to the faucets, toilet, and shower. Some RV pumps sense pressure within the system to maintain it, while others will maintain a constant flow rate regardless of pressure. RV pumps operate at 12 volts, so they can wire in directly to the RV’s 12-volt system. When a fixture is opened in the RV, the water pressure within the water lines drops. When the pump detects this low water pressure, it will power on to maintain consistent pressure. Once this pressure is reached, it will shut off until a fixture is opened again. As a result, RV pumps do not run often unless there is a leak somewhere in the RV.

Learn more: How to fix RV water pressure problems

RV running water

Types of RV water pumps

The three most common types of RV water pumps are constant speed, variable speed, and high volume.

Constant speed RV pumps

The most common type of RV pump, constant speed pumps deliver water at a consistent speed regardless of application. They are the most inexpensive type of RV pump, but they tend to have the shortest lifespan of the three types. Because they do not fluctuate motor RPM like variable speed pumps, constant speed pumps can run longer than necessary. Over time, this causes the pump to die quicker than the other pump types.

Variable speed RV pumps

Variable speed pumps raise and lower the motor's RPM to maintain a more constant pressure based on demand. They are more expensive but also more efficient, creating less noise, enabling a longer lifespan, and consuming less energy.

High volume RV pumps

High volume RV pumps are used in large applications, such as motor homes and bus homes. They deliver flow rates of over 4 GPM to accommodate the need for higher volumes of water. In standard RVs, these pumps are unnecessary.

How to prime an RV water pump

Before being used to pump water through an RV, an RV water pump must be primed to avoid damage caused by air in the system. An RV water pump should be primed when you are installing a new pump, if your pump has just been repaired, after sitting idle for an extended period, and after de-winterization. If your pump is running with low water pressure, inconsistent flow rate, or excessive noise, it may need to be primed to operate normally. Follow these steps to prime your RV water pump:

  1. Fill the fresh water tank. You can use a gauge to ensure the tank is full.
  2. Disconnect the pump from all water sources. This includes a city water connection and the fresh water tank.
  3. Open one cold water tap inside the RV. This eliminates air in the line. It is a good idea to open the tap closest to the pump. Keep all other fixtures and faucets closed.
  4. Switch the pump on.
  5. Pour water into the hose connected to the pump inlet. You may wish to use a funnel for this step.
  6. Ensure water is flowing through the pump. If water is not flowing through the pump, attempt this process again.
  7. Shut the pump off and reconnect the inlet line. Once the poured water has flowed through the pump, shut the pump off and reconnect the hose to the inlet line.
  8. Turn the pump on and inspect. The water from your fresh water tank should now be flowing through the pump. Inspect for leaks, low water pressure, or any other problems related to the pump.

How to maintain an RV water pump

For your pump to operate optimally for a long period of time, you should perform a few simple maintenance tasks regularly. These include:

  • Annual RV inspection. A yearly inspection of your RV can grant you peace of mind that your pump and other RV components are working optimally. These inspections should include water lines within the system, which can cause a pump’s life to be shortened when a leak is sprung.
  • Cleaning the filter. This filter does not refer to your water filter, but rather the filter between your fresh water tank and pump. This strainer keeps unwanted debris from entering your pump and damaging it. Regularly clean off the filter to keep it operating efficiently.
  • Sanitizing your water lines. Sanitization of your RV’s water lines is particularly important when the RV has sat unused for an extended period. When left unattended, algae can grow in your lines and enter your pump, causing costly damage. The water lines are often sanitized during an annual inspection.
  • Testing your pump before you leave. No matter where you are traveling, you should always test your RV water pump before you leave. A failed pump is much easier to address at home than when water is needed from the RV.

Inside of an RV

When should I turn my RV water pump off?

An RV water pump should be turned off at certain times to prevent damage to the pump or the RV’s plumbing, or as a precautionary . These scenarios include:

  • At night. If a water leak occurs during the night, you do not want to be sleeping so that the problem cannot be addressed. Some pumps are also loud and can disturb sleep if they power on in the middle of the night.
  • While on the road. Rough roads can cause a faucet to turn, leading to wasted water before you get to your destination.
  • While connected to city water. Because city water is already pressurized, it does not need to flow through the pump. If the pump remains on while your RV is connected to city water, you will waste water from your fresh water tank.
  • When leaving your RV for an extended period. While there will most likely be no issues with your RV water system while you are gone, you can have peace of mind that your pump will not activate when a leak forms if you shut your pump off.

Common RV water pump problems

You may run into multiple problems with your RV pump during its lifecycle. For each issue an RV water pump may present, there is a sequence of checks you can make to find a solution.

The pump is not starting

If your RV water pump is not starting, it could be caused by one of a few issues. First, check that the RV’s battery is not low. If the battery is fully charged and the pump still does not start, there is likely a problem with the pump switch, the wiring, or the pump itself. Check for any loose wiring or broken fuses. If the wiring is loose, ensure that you disconnect all power sent to the pump before attempting to fix it. Replace any broken fuses if needed. If none of these fixes allow the pump to start, consult a professional to inspect your pump.

The pump runs while you are not using water

If your RV water pump continues to cycle when you are not using water, there is likely a leak somewhere in the system. When a leak opens in an RV’s plumbing, the water pressure drops, and the pump will attempt to keep it constant. Once the leak is repaired, the pump should continue to operate only when needed.

Learn more: How to find and fix RV water pressure problems

The pump is running, but no water is coming out

If your RV water pump is pumping, but your fixtures remain dry, ensure that:

  • There is water in the fresh water tank.
  • There are no loose connections on the pump’s inlet or outlet.
  • There is water flowing to the pump. Disconnect the line between your tank and the pump. If water exits the line as you disconnect it, water is reaching the pump. If not, check the water line for damage. If not damaged, fill the line with water and reconnect it to the pump.

If none of these fixes resolve your problem, there is either a problem with the lines between your pump and the fixtures, or the pump itself is dead. Consult a professional for assistance.

The pump is too loud

A loud RV water pump may be caused by the inherent design of the pump or improper installation. RV pumps are noisy by nature, but the noise levels can be reduced by preventing the pump from rattling against metal in its installed location. To reduce the noisiness of the pump, secure it to a rubber or felt pad and ensure it is not loosely installed.

Learn more about RV water systems: 5 of the best RV water filters

The pump pulsates on startup or just before shutdown

Pump pulsation is also referred to as rapid cycling and is usually the cause of the shut-off pressure setting on the pressure switch being too low. Most pumps have an adjustment screw on the pressure switch that can be turned by either an Allen wrench or a Phillips head screwdriver. Turn the adjustment screw slightly clockwise to increase the shut-off pressure until the cycling stops. Make sure you turn the adjustment screw slowly during this process.


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