Do you leave the water pump on in an RV?

In this article, we will answer the following question: Do you leave the water pump on in an RV? We will explain how an RV water pump works and how to troubleshoot the most common of this device’s failures. 

Do you leave the water pump on in an RV?

You should not leave the water pump on in an RV if you are connected to the city water supplies. The reasoning is simple: the water you use in the RV will be provided externally, thus you do not need the pump to be on. 

If you are in a camp that has a connection to the city water, you can use this source directly. Attach the lateral hose to the municipal water system. This connection does not require the water pump to be used.

If you want to use water from the clean water tank, only then you must turn on the 12V water pump. The switch for the water pump is located on the control panel. On some A-Class models, there is a second water pump switch located in the bathroom.

Caution: There are some campgrounds where the water pressure is so

high that can rupture the water pipes of the motorhome, causing leaks. The pipes can withstand only 45 psi. It is MANDATORY that you use the water pressure regulator provided with the water hose.

Thus, if the water pump switch is left on the ON position, this WILL break the tubing because it will be too much pressure. 

How does an RV water pump work?

The primary function of an RV’s water pump is to pressurize water from the engine and the pump stored directly in the engine. The water pump is an integral part of an RV’s cooling system, which also includes the radiator and assorted hoses. 

The water pump consists of a small inner propeller surrounded by a metal casing that bolts directly to the engine block. The rotational movement of the propeller creates the pumping action of the water pump.

Attached directly to the front of an RV’s water pump is a small pulley mechanism on which the water pump belt rides. This pulley is directly attached to the propeller of the indoor water pump; the drive belt fits snugly on the pulley and provides the turning action that powers the water pump impeller. An RV’s water pump would be non-operational without its pulley and belt drive mechanisms.

Water pumps come in a variety of sizes. Larger vehicles with engines and/or larger vehicles designed for heavy use usually come installed with larger water pumps. 

An RV is a large, heavy vehicle that is typically used for long-distance driving combined with large-scale towing applications. This calls for the use of a larger, more powerful water pump to handle the increased operating temperatures and stresses of a recreational vehicle.

The water pump hose is large, rubberized water pump hose supports the function and use of a motorhome water pump. This hose, which is heat resistant and responsible for funnelling pressurized water from the water pump directly into the engine radiator, is a vital link in an RV’s overall cooling system. A leaky or malfunctioning water pump hose can cause overheating, radiator failure, and engine damage.

RV water pump common problems and solutions

We often get asked how to fix certain RV water pump issues. Below are the most common problems and a guide on how to fix them.

  • Pump head leak

Immediately begin turning off the pump and closing all the water valves leading to it. Check the bolts around the pump head and tighten if necessary. It is possible that the diaphragm of the switch at the front of the head has been punctured by debris coming through the water inlet valve. 

Check this by unbolting the diaphragm casing from the pump switch. The drive assembly gears should be visible on the water pump with the casing removed. If there is water or condensation on the gears, then the switch diaphragm has been punctured. It is a thin plastic plate inside the latch housing. 

This must be replaced, and the entire unit will have to be serviced by professionals to eliminate the danger of long-term water damage.

  • The pump works but does not cause water flow

First check the purge valves attached to the RV’s water tank, hot water heater, and faucets. Involve all of them to make sure there is no air in the lines, preventing the water pump from moving. Similarly, make sure the water tank has water in it. 

Close the water inlet valve connected to the pump and unscrew the disk-shaped filter on the connecting line. Open the filter and clean it of all debris that may be impeding the flow of water. Reassemble the filter, connect it to the pump, open the water inlet valve, and start the pump again. 

If no water is flowing, then there is a loose connection in the water supply lines that are preventing the water pump from moving, or the pump housing is cracked and unable to create a vacuum.

  • Pump cycles continuously

The pump is cycling as you think you are not generating enough water flow. If the water shutoff valve has closed, open it. If there is a water purifier or filter connected to the inlet line of the pump, it will slow down the water intake, causing this problem. The water filters must be connected to the outlet port of the pump, not the inlet port. 

Lastly, check the pressure switch. It should be attractive when the water pump has done its job, preventing cycling. Since there is no obstruction preventing sufficient water flow, the pressure switch activation threshold is too high and must be adjusted.

Troubleshooting an automatic RV water pump

An RV’s water pump failure is generally caused by a bearing failure in the pump shaft accompanied by a water leak. Water leakage is generally witnessed coming out of the drain hole at the bottom of the pump. 

There may also be a leak around the gasket behind the pump. Sometimes the water pumps have to be seen to leak at a certain point on the bearing surface. A water pump definitely does not leak when the engine is off, so it must be pressure tested when the engine is running.

In almost all cases, a bearing failure will cause the pump shaft to become loose and can be tested by grabbing the fan and wobbling. If the pump shaft moves when wobbled, it is obvious that the shaft is worn. 

The water pump will also give an audible signal that is easy to detect. Care must be taken to replace the water pump as soon as possible, as it can become blocked, causing the accessory strap to be removed. If the tape comes off, in many cases, you too will lose power steering. Every now and then the pump will break down and possibly go through the radiator and ruin the radiator as well.

Use a radiator pressure gauge for this test. Remove the radiator cap when the engine is cold. Fill the radiator as needed to bring it to a normal level. Pump the pressure tester up to 15 pounds and look closely at the water pump for leaks. 

If leaks are present, the pump needs to be replaced. While the pressure tester is being pumped up, check for leaks at the radiator, hoses, top of the engine for intake manifold leaks, side of the engine for freeze plug leaks, and at the heater core.

One more area that needs to be tested and considered is the water pump pulley. While this may or may not cause a leak, it can cause the water pump to stop working. Check the pulley for out of round or warping. This could cause an equilibrium condition that is quickly worn by the water pump bearing. 

Start the vehicle once the pump is replaced and watch the water pump pulley to see if it bounces. Replace the pulley if it shows all year round. You can also see the fan for form and function and replace it as needed.

FAQ on Do you leave the water pump on in an RV?

Can I fill a water tank from the bottom?

Yes, you can fill a water tank from the bottom, and it will cut down the time that the tank is filled and the energy consumption. 

How do you fill a hot water heater?

To fill a hot water heater you have to first fill the freshwater tank. Use a water pump for this and be careful not to overfill your tank!

How long does it take to fill the RV water tank?

It takes about 20 minutes to fill an RV water tank. It all will depend on the size of the water tank and how fast the water flows.


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