Awe, the mystery of the RV water pump.  Few people actually understand how the water system works in their RV.  If you have a 5th wheel, motor home, camper, or tent trailer, they are all basically the same so you've come to the right place to learn about them.

Chances are that if you found your way here, you are having problems with your RV water pump. Fear not.  The system is relatively simple and easy to repair.

The RV water system consists of a fresh water holding system, plastic or copper water pipes, a 12 volt RV water pump, a gray water tank, and a valve for dumping.

We're only going to cover the RV water pump in this article. RV water pumps are relatively simple devices.  The most common manufacturer these pumps is ShurFlo.  These pumps are nearly always powered by 12 volt DC electricity.  Even if you are plugged into a 120 volt AC power at a RV campground, they still use 12 volt power.  This is accomplished by the 120 volt AC power being directed into a power converter than changes the 120 VAC into 12 VDC electricity.

The RV water pump is an on demand system.  This means that the pump only kicks on when it's needed.  They work by presurizing your water pipes to a preset PSI (pounds per square inch).  This is usually about 30 PSI but most pumps are adjustable.  When the power is switched on to the pump, it starts pumping.  If any faucets are open, the pump continues to run providing the necessary flow of water.  When you shut the faucet off, the pump continues to run until the preset water pressure is built up in the plumbing lines.  When this pressure is reached, the pump automatically turns off.  These pressure in the line is maintained until you open a faucet again.  When you open the faucet, the pump senses a drop in pressure and begins pumping again.

Some older RV water pumps work differently.  You have to manually turn the pump on when you want water.  You open the faucet, turn the pump on and water flows out of the faucet.  When you want to turn the water off, you turn the switch off to the pump and then close the faucet.  It's important to do things in this order.  These older pumps don't shut off when the water reaches a preset pressure in the line.  Leaving the pump running will either overheat the pump or burst a plumbing line.

Like any system in an RV, there are things that can sometimes go wrong. Below are the procedures for troubleshooting your RV water pump.

1. Is there water in the holding tank. Believe it or not this is often overlooked. It's possible for the water gauges to accumulate residue on them and read full when they are in fact empty.
2. Make sure there is power to the pump. Is your RV battery fully charged? If not, you can plug into 120 volt power to make sure you have power to the pump. There is usually a fuse in the positive wire somewhere near the pump. Check the fuse to see if it is blown. If it's blown, replace it and your problem is usually solved. Check to see if the connections to the pump are good. Since RV's usually travel the road, it's possible for these connectors to come loose. If the fuse is good, use a 12 volt test light or better yet a multi-meter to check for power at the pump. If you don't have power, check the connections at the battery and the power converter. If they are bad, repair them and your problem should go away. If they are good, you want to inspect the wiring for breaks or shorts. If there are bad spots in the wiring, you will need to repair or replace the wiring. Another thing that can fail is the switch to the pump. The easiest way to test this is to bypass the switch and connect the RV water pump directly to the positive and negative wires. If you do this and the pump functions normally, the switch needs to be replaced.
3. If the pump comes on but doesn't pump water, it's possible that the diaphragm in the pump has debris in it or it is punctured. There are three screws that attach the pump head to the pump casing. Remove these screws and inspect the rubber diaphragm. If it is damaged, replace it with the repair kit that you can get from the manufacturer. You can usually buy these at your local RV parts dealer. If the diaphragm looks okay, clean it thoroughly with a gentle detergent and flush the pump head to remove any debris that may have entered it. If it still doesn't work after doing these procedures go the next step.
4. Check to see that supply line from the fresh water holding tank to the RV water pump isn't blocked for punctured. Sometimes there is a shut off valve on this line. Make sure that it's open. If the line is blocked with debris or ice, you'll need to clear it somehow. I have found that I can often disconnect the line at the pump and blow compressed air through the pipe. Be sure and turn the pressure down low on the compressor. You don't want to blow the line and cause a leak. If there is a leak in this supply line, it will need to be repaired or replaced. You may also want to check the connection at the inlet side of the pump to make sure it isn't sucking air.
5. If the pump doesn't shut off. You likely have a leak somewhere in the system. It's either at the outlet connection on the pump, in the plumbing, or at the faucet. Find the leak, repair it, and you'll be back in business.

That's all I can think of off the bat that can go wrong with the system. If none of these things fix your RV water pump sent me and email and I'll try to help you out.

You and you alone are responsible if something should go wrong while repairing your RV water pump system.  If you are not skilled and competent with electrical wiring or plumbing, you should have an authorized dealer do the repairs.  There is always a risk of fire when working with electrical wiring.  If you should make a mistake on the plumbing, it's possible for your RV to floods and cause damage.

If you mess up, don't count on me to foot the bill for the repairs.  The information contained in this page is only the opinion of the author.  This is what I would do if my RV was having problems with the RV water pump system.

Make any repairs at your own risk.