What Size Wire Do You Need for a Well Pump? A Complete Guide
We’re diving into well pumps, specifically focusing on wire sizes and how to properly wire a well pump system.
If you’re a homeowner dealing with a well system or just curious about how these setups work, this one’s for you.
Two Main Types of Well Pumps
There are two primary types of well pumps you’ll come across in homes:
- Deep Well Pump
- This pump is submerged down into the well.
- Typically used for drilled wells.
- Often requires a four-wire setup (including a ground).
- Jet Pump
- Installed above ground, usually inside the house.
- Uses a suction line that pulls water from the well (dug or drilled).
- Equipped with a foot valve to keep water from draining back.
How a Deep Well Pump System Works
Behind me, we’ve got a typical deep well pump system set up:
- Disconnect Switch: Connected to a 240V feed from your main panel.
- Pressure Tank & Pressure Switch: These components regulate the pressure in your water system.
- Starter Box: Controls the pump operation.
These systems usually run on 240 volts, single-phase. Depending on the distance from the panel, they require either 12-gauge or 10-gauge wire. Here’s how it all connects:
- From the Panel: Power runs into the disconnect (often using 10 AWG wire).
- From the Disconnect: Wire continues through the pressure switch.
- Pressure Switch: Detects when pressure drops and closes the circuit.
- Starter Box: Activates the pump when needed.
Inside the Starter Box
Now for the part you’re probably here for — the starter box.
Inside, you’ll find:
- A relay
- A capacitor
- A wiring diagram
- Terminals for red, yellow, and black wires (for a 3-wire pump)
This wiring setup is standard for 3/4 HP deep well pumps and allows for efficient starting and operation of pumps placed deeper down the well.
Choosing the Right Wire Size
The deeper your well, the more amperage your pump draws — and the larger the wire size you’ll need to prevent voltage drop. Here’s a quick reference:
| Pump Depth | Typical Wire Gauge |
|---|---|
| Up to 100 ft | 14 or 12 AWG |
| 100–200 ft | 12 AWG |
| 200–400 ft | 10 AWG or larger |
Even for pumps that are only 1/2 HP or 3/4 HP, deeper wells require lower resistance wire (larger gauge) to handle the load efficiently.
Jet Pump Wiring Basics
Jet pumps, which sit inside the house, are more straightforward:
- Usually 1/2 HP or 3/4 HP
- Wired with 12/2 or 10/2 cable
- Can be configured for 120V or 240V
Note: If wired for 120V, the pump draws more amperage, which is why larger wire (like 10 AWG) may be used. At 240V, the amperage drops, making 12 AWG the more common choice.
Example: Real Numbers
A 1/2 HP deep well pump at 100 feet drawing 4 amps at 240 volts isn’t pulling a ton of power. In this case, 12 AWG wire is more than enough — sometimes even 14 AWG depending on the installation and code requirements.
Final Thoughts
To sum it all up:
- Know what type of pump you’re working with (jet vs. deep well).
- Determine the pump’s horsepower and depth.
- Use larger gauge wire (10 AWG or lower number) for deeper wells to prevent voltage drop.
- Stick to 12 AWG as the most common size for shorter runs and residential systems.
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