Submersible Well Pump Wiring Diagrams

Old well pump

Whether you're installing a new well pump or you're replacing an old one, submersible well pump wiring diagrams can help you better understand how the well pump operates.

Types of Submersible Well Pump Wiring Diagrams

If you're installing a new well pump yourself, or you've hired a local well contractor to do the job, you should always receive the documentation that comes along with the water pump that's installed in your drilled well. Even though a submersible well pump gets dropped a hundred or more feet below the surface of the ground into the water at the bottom of your well, much of the wiring and controls for that well pump exist inside your house.

How a Submersible Pump Works

After a well system is properly connected, the operation is as follows.

  • The well pump turns on long enough to pump water into your expansion tank to increase the water pressure to a certain preset level.
  • As you use water in your house, the pressure in the expansion tank decreases.
  • When the water pressure decreases beyond a certain level, the pressure switch sends the "on" power signal to the well pump.
  • The well pump turns on and once again pumps more water into the tank until the pressure climbs back to the upper pressure limit.

This is generally how any well system works in a house that gets incoming water from a private well.

It's important to understand how your well is wired, so that you can quickly troubleshoot issues when things go wrong. There are generally two basic types of submersible well pump wiring diagrams, the 2-wire and the 3-wire diagram.

A 2-Wire System

The type of wiring system used for submersible pumps is typically based on the size of the pump itself. Smaller pumps usually have a simple 2-wire diagram because they only require a simple power connection to start. This makes wiring fairly easy, because the power from your home circuit box goes directly to the water pressure switch, and from there to the well pump. Wiring is fairly straightforward, because terminal connections are clearly marked inside the pressure switch. So long as you correctly wire the positive and negative terminals to the correct wires from both the incoming power and the well pump wiring, everything will work perfectly. Don't forget to hook up ground wires as well!

A 3-Wire System

Many people think that the 3-wire system refers to a "three-phase" power system, but this isn't the case at all. The three wires refer to the three colored wires that come from larger submersible pumps. These are typically yellow, black and red wires coming from the well pump to the control box. The control box is the central wiring point for this system, and it's where the three colored wires come in, as well as where the incoming power from the pressure switch are also connected. The 3-wire system is necessary for larger pumps because these pumps require a special "start-up" process.

  • The red cable only gets energized temporarily until the pump comes up to speed
  • Then the control box switches operating power over to the black wire
  • The yellow wire is the "common", not to be confused with the green "ground" wire that must be connected to your main power ground connection.

The 3-wire system isn't much more complicated than the 2-wire system, but it does require that the correct wires get connected to the correct terminals inside the control box.

Where to Find Submersible Well Pump Wiring Diagrams

You can find many diagrams for the two types of systems described above. As a homeowner, even if you never plan to install or change a well pump on your own, it's important to know how the system is wired so that you can change out components like the pressure switch if necessary.

  • At GreenRoadFarm, you'll find a full installation and troubleshooting guide that covers everything from installing the new pump to wiring the control box and pressure switch to the circuit breaker. About three quarters of the way through the page, you'll see diagrams on how to wire both a two-wire system and a 3-wire system that includes a control box.
  • At DIY Chatroom, you'll find an interesting wiring diagram of the well pump control box including the start and run capacitors that are triggered by the red and yellow wires from your pump. This diagram is an excellent way to understand exactly what the control box does.
  • At AllExperts, you'll find a small wiring diagram showing a configuration where a generator is connected to a well pump so that there's still water flow to the house even when the electricity goes out.
  • Popular Mechanics is a great place to go if you just need a "big picture" diagram of how the well pumping system is typically configured and where are the components are throughout the system.

Safety Concerns

Keep in mind that any electrical system can have voltage or current levels that are life-threatening. If you're uncertain or nervous about dealing with electricity, call in a professional. If you know what you're doing, always take the first step of "locking out" the entire system by shutting down electricity at the circuit breaker box. Use an appropriately sized electric meter to ensure that the system has no electricity before making any wiring changes. By using well pump wiring diagrams to understand how your well system works, you'll have a much better idea what part of the system probably failed when things do go wrong.

Submersible Well Pump Wiring Diagrams