As an RV owner, you are likely familiar with your water system pump noise. Seems like every time someone in the RV uses the water, you know about because of the familiar noise from your water pump.
But, sometimes, that pump noise sounds different. It’s not a normal pumping noise but rather a humming noise. Why?
The most common reason your water pump makes a humming noise is insufficient pressure in the water line. A few things that can cause this lack of pressure are an open valve, a pipe leak, or even low battery voltage. This post will review these common causes, including:
- How your RV water pump uses pressure
- The four common issues that can cause humming
- The best way to fix these issues
Table of Contents
- Water pump
Your RV needs water pressure, so all you have to do is turn a knob so the water freely pours out. When you have a city water connection, your RV water system uses the already-supplied water pressure for things such as your faucet and toilet.
But when you are not connected to city water and rely on your fresh water tank, you need the water pump to create pressure to operate your faucet or shower. Certain principles and functions need to occur for your pump to work properly.
When your RV water pump is humming, it is most commonly caused by incorrect water pressure, and your pump stays on until it senses the correct pressure. Let’s start to review what can cause this pressure issue and see how to fix it.
An RV water pump is a basic pump that will take water from your fresh water tank, which is usually below or on the floor of your RV. A hose goes from the fresh water tank to the pump.
Your water pump also has a pump pressure switch on the pump housing. Near the pump head, this sensor tells your pump to turn off or stay on until the desired pressure. Things such as air or debris can throw off the pressure in the water system, triggering your pump to stay on and hum. Let’s look at some common issues regarding what makes your pump humming.
Issue #1: Pump Priming
Since the water tank is usually below the tank’s water line, the pump must “prime.” This means air is in the water line, which must first fill with water before it operates properly. Remember, this is a water pump, not an air pump, so it needs water in the line to start the “suction” process from the tank to the pump. Any air in the suction line will cause the pressure to be off.
Another cause of the priming issue could be insufficient water in the freshwater tank. The pump takes in air and water once the water level gets too low. Since air can compress, the water pump will keep running or humming as it tries to pressurize water and air.
Solution: Check the fresh water tank level
The solution to this humming is ensuring you have enough water in the fresh tank. Sometimes, your water sensors may be off, so ensure you have at least a quarter of the tank full to allow your pump to operate. It may take 20 to 30 seconds to stop humming, but once the hose line is primed, the pump should function normally.
Issue #2: Air in water system
Any air in your water system will cause the water pump to hum until the water pressure is met. Here are a few spots that commonly cause air in your water line.
Your RV has valves everywhere. Your freshwater tank, hot water heater, low point valves, and even a faucet valve. When the valve is meant to be closed during normal operation, for example, your low point valve, any leak in the valve will cause air to get into your system. To fix this, check your low point valves outside your RV and ensure they are secure and not leaking (water dripping).
Another place air can enter is your winterizing valve. This can either be a leaking valve or the valve turned in the winterizing position when you don’t mean it to be. When you are winterizing, you use a bypass valve that will take water from a separate winterizing hose (for antifreeze) versus the fresh water tank. If this valve setting is in the wrong position or not closed all the way, water could enter your system and cause the water pump to hum.
Another point where air can enter is the water heater. Since an RV water heater is periodically drained or not in use, air is easily entered into the water supply through the water heater. To fix it, first, check that there is no remaining air in your tank. To do this, turn on the hot to your faucets, letting the water flow and ensuring all air escapes. This is for all your faucets, including the tub and even an outdoor shower if you have one. Air can be anywhere in your line, so you must release it from all faucet locations.
Next, check your anode rod or drain plug for leaks. It doesn’t need to be a large leak, but any drips at your anode rod can introduce air into the system. If you see a leak, use Teflon tape around the rod threads for the plug. Teflon tape helps seal the threads and can reduce the chance of air entering.
Issue #3: Debris
Believe it or not, there is debris in your water line. This can either be from your water supply or, more commonly, the construction of your RV. I recall one RV I had where the pump kept humming and eventually stopped working. After replacing it with a new pump (luckily still under warranty), I discovered that the inside was full of plastic shavings. These shavings were from the drills they used in construction, and the plastic pieces just remained in the pipe. As I used water in the RV, this plastic entered the pump housing and eventually caused enough damage for the pump to stop working. From then on, I made sure I had a good water filter and that it was clean.
The fix is to make sure you have a clean water filter. These are next to the water pump. Check it to see all is clear and that water is flowing through. If there is any visible debris, replace the water filter.
Another common cause of your RV water pump humming is low battery voltage.
Issue #4: Low battery voltage
Your RV water pump runs on 12 volts from your RV battery. Even when plugged into shore power, the power still comes from your battery for the pump motor. As you use your RV battery, and without recharging, the voltage starts to drop. As your voltage drops, so does your ability for the pump motor to operate. Once the voltage gets around 10.5 volts, the pump motor will not have enough power to get the pressure where it needs to be to turn off. As a result, it will keep humming until it gets the needed power to get to the correct water pressure.
The fix is to check your battery voltage and ensure you have at least 12 volts. If not, charge your battery through shore power, a generator, or solar panels.
Having your RV water pump humming but not pumping is usually a simple issue that can be investigated and fixed by many RV owners. Knowing that a pressure issue causes this humming, you can investigate and fix the common problems. Ensuring that your pump system is primed from the fresh tank is a first start. Then, ensure all air is released from your pipes by turning on all the faucets. You can also check for debris that may have entered your system. Finally, check for low battery voltage that will not give your pump motor enough power to get to the correct pressure.
Tony is an avid camper and RV traveler. He fell in love with camping on his first RV trip with his wife over 25 years ago. Tony loves sharing lessons learned and tips about RV maintenance and safe traveling.