Well Irrigation System: Watering a Yard From Your Well

Most sprinkler problems on a private well start before the first trench is dug: someone designs the zones around the lawn instead of around the well. A well irrigation system can only deliver as much water as the aquifer refills and the pump can push, so the gallons per minute your well produces set the size of every zone. Get that number first and the rest of the design falls into place.

The short answer for most homeowners is this. Have the well’s sustained yield measured, design each zone to use no more than about 70 to 80 percent of that flow, and decide whether the existing house pump can handle irrigation or whether a dedicated irrigation pump (or a separate well) makes more sense. Add proper backflow protection so lawn water can never siphon back into the drinking supply, and leave every electrical connection to a licensed electrician.

Done well, watering from a private well can cut or eliminate outdoor water bills. Done poorly, it can burn out a submersible pump, drain a low-yield well during a dry spell and leave the house without water at dinnertime.

How a Well Irrigation System Works

On a city-water sprinkler system, the utility supplies steady pressure and nearly unlimited volume. On a well, three components share the load: the aquifer, which refills the well casing at a certain rate; the pump, which lifts water and pressurizes it; and the pressure tank, which buffers demand so the pump does not start and stop every few seconds.

When a sprinkler zone opens, the tank pressure drops, the pressure switch turns the pump on, and the pump runs continuously as long as the zone draws water. Ideally the pump runs steadily for the whole zone cycle. If the zone demands more than the pump can produce, pressure sags and heads spray weakly. If it demands far less, the pump cycles on and off rapidly, which shortens motor life. A matched system keeps the pump running in one long, steady run per zone.

Many installers search for a “well pump irrigation system” or a “sprinkler well pump” as if the pump alone were the system. In practice the yield of the well matters just as much, which is why the first step is a measurement rather than a shopping trip.

Step One: Check Well Yield Before Adding Zones

Well yield is the sustained flow, in gallons per minute (GPM), the well can supply over an hour or more without the water level falling to the pump intake. Your well log, often on file with the state or county, may list a yield from the day it was drilled. Treat that figure as a starting point, since yields can drop over decades as screens clog or water tables shift.

A licensed well contractor can run a pump or draw-down test to confirm the current yield. As a rough guide:

• Under 5 GPM: marginal for irrigation. Drip lines or a storage tank refilled slowly overnight are usually safer than spray heads.
• 5 to 10 GPM: workable for small zones of drip, bubblers or a few rotors, run one zone at a time.
• 10 to 20 GPM: comfortable for typical residential rotor and spray zones.
• Over 20 GPM: enough for larger lawns, though pump capacity may become the limit.

You can also do a simple bucket test at an outdoor spigot near the pressure tank to see what flow the pump delivers at working pressure. Time how long a 5 gallon bucket takes to fill and divide 300 by the seconds. A 20 second fill means about 15 GPM. That shows pump output at that moment, not long-term well yield, so it complements a pro test rather than replacing it.

Sizing Zones to Pump Capacity

Once you know usable flow, add up the flow rating of each head on a zone. A spray head might use 1 to 2 GPM, a rotor 2 to 5 GPM, and a drip zone a fraction of a gallon per emitter. Keep each zone’s total at roughly 70 to 80 percent of the lesser of well yield and pump output. That margin covers friction loss in long pipe runs and keeps household taps usable if someone showers during a cycle.

Pressure matters too. Most spray heads want 30 PSI or more at the head, and rotors often perform best around 40 to 50 PSI. A standard 40/60 pressure switch setting delivers that range, but long runs uphill or undersized pipe can cut it quickly. Your installer will look at the pump curve, which shows flow at each pressure, to confirm the pump can deliver your target GPM at the needed PSI.

1. Record well yield (from a pro test) and pump output (from a bucket test).
2. Take the smaller number and multiply by 0.75 for your maximum zone flow.
3. Group heads so each zone stays under that maximum.
4. Run zones one at a time, never overlapping, and stagger long cycles so the well can recover.
5. Schedule watering for early morning, when household demand is lowest.

House Pump vs Dedicated Irrigation Pump

Using the house pump is the simplest route. The irrigation main tees off after the pressure tank, the controller opens valves on schedule, and the existing pump does the work. This suits small yards and wells with healthy yield. The trade-off is extra run hours on the pump that also supplies your drinking water, plus a pressure drop indoors while zones run.

A dedicated irrigation well pump separates the two jobs. Some homeowners add a second pump on the same well (where yield and casing size allow), while others drill a separate shallow irrigation well. For shallow water, an irrigation jet pump mounted above ground is a common choice because it is easier to service and can lift water from roughly 25 feet or less. Deeper water generally calls for a submersible pump.

A separate well also keeps untreated irrigation water away from any treatment equipment inside the house, so a softener or filter is not wasted on the lawn. Many controllers can trigger a pump start relay, which switches the pump on only when a zone opens, a setup that must be installed by a licensed electrician.

Backflow Prevention: Protecting Your Drinking Water

Sprinkler lines sit in soil that can contain fertilizer, pesticides and animal waste. If pressure in the house drops suddenly, water in the irrigation pipes can be pulled backward into the well or plumbing. A backflow prevention assembly stops that reverse flow, and most jurisdictions require one on any irrigation connection to a potable supply.

The right device (pressure vacuum breaker, double check valve or reduced pressure zone assembly) depends on local code, whether chemicals are injected into the system and how the lines are laid out. Selecting, installing and annually testing that device is a job for a licensed plumber or certified backflow tester, not a weekend DIY task. Many areas require a test report filed after installation. A sanitary well cap that keeps insects and surface water out of the casing belongs on every well regardless of irrigation.

Drilling a Separate Irrigation Well

If your house well is low yield, irrigation well drilling may be the better long-term fix. Shallow well drilling for irrigation reaches the upper water table and avoids taxing the deeper aquifer that supplies the house. Local rules govern setbacks from septic systems, property lines and buildings, and most counties require a drilling permit and a licensed driller.

Irrigation well cost varies widely with depth, geology and region. Shallow driven or jetted wells in sandy soils can cost a few thousand dollars, while drilled wells through rock that need casing and a submersible pump commonly run from several thousand to well over ten thousand dollars. Ask for quotes that separate drilling, casing, pump, electrical and permit costs so you can compare bids fairly. Call 811 before any digging for lines or trenches.

Electrical Safety for Irrigation Pumps

Pump circuits are line voltage, often 240 volts, and run outdoors near water. Any new circuit, pump wiring, pump start relay or controller connection to line voltage belongs to a licensed electrician. Outdoor receptacles for controllers must be GFCI protected and in weatherproof covers.

For routine homeowner tasks, such as cleaning a controller enclosure or checking a wire nut on a low-voltage valve wire, turn off the breaker and confirm power is off with a non-contact voltage tester before touching anything. Valve wiring from the controller to the solenoids is low voltage (typically 24 volts AC), but the controller transformer and the pump circuit are not. Never test live circuits or measure voltage on powered equipment yourself. Resistance checks on valve solenoids should only be done with the controller unplugged.

Troubleshooting Common Problems

• Weak spray on one zone: too many heads for the available flow. Split the zone or swap to lower-flow nozzles.
• Pump short-cycling: zone demand is too low, or the pressure tank is waterlogged. Have a pro check the tank air charge.
• Sputtering or air in lines late in a cycle: the well is drawing down. Shorten run times and add soak breaks so the well recovers.
• Sand in heads: add a filter ahead of the valves and ask a well pro about the pump intake depth.
• House loses pressure during watering: move irrigation to off-peak hours or consider a dedicated pump.

General Cost Ranges

Adding sprinkler zones to an existing well with an adequate pump often costs about the same as a city-water installation, plus the backflow assembly. Upgrading to a larger pump or adding a dedicated irrigation pump typically adds a few hundred to a couple of thousand dollars for equipment, plus electrical and labor. A new irrigation well is the largest expense. Yield tests by a well contractor usually cost a few hundred dollars and are worth it before you buy anything.

When to Call a Licensed Professional

Bring in a licensed well contractor for yield testing, pump selection and any work inside the casing. A licensed plumber or certified tester should install and test backflow devices, and a licensed electrician should handle pump circuits, relays and outdoor receptacles. Permits are commonly required for new wells, backflow assemblies and electrical work, so ask each contractor which ones they will pull. A homeowner can still plan zones, choose heads and set schedules once those pros have confirmed the numbers your well irrigation system has to live with.