Well Depth Explained: How Deep Should Your Well Be?

What Determines Well Depth?

Primary Factors

• Geology: Where water-bearing rock formations exist
• Water table depth: How far down groundwater is found
• Aquifer quality: Need to reach productive zone
• Regional conditions: Local aquifer characteristics

Driller's Decision Process

1. Review geological data and nearby well logs
2. Drill until hitting water-bearing formation
3. Test water quantity and quality
4. Continue deeper if needed for better water
5. Add buffer depth for drought protection

Static Water Level vs Well Depth

• Well depth: Total depth of the borehole
• Static water level: Where water naturally sits when not pumping
• Pumping level: Where water drops to during pumping

Example: A 300-foot well might have static water at 100 feet, leaving 200 feet of water column.

Shallow vs Deep Wells

Shallow Wells (Under 100 feet)

• Pros: Less expensive to drill, cheaper pumping costs
• Cons: More vulnerable to contamination, may go dry in drought
• Common in: Areas with high water tables

Medium Wells (100-300 feet)

• Pros: Good protection from contamination, usually adequate water
• Cons: Moderate drilling and pumping costs
• Common in: Many suburban and rural areas

Deep Wells (300+ feet)

• Pros: Best protection, most reliable during drought
• Cons: Higher drilling cost, more expensive to pump, harder to service
• Common in: Arid regions, mountainous areas

Average Well Depths

San Diego County

National Averages

• Eastern US: 100-300 feet typical
• Midwest: 50-200 feet
• Western US: 100-500+ feet
• Arid Southwest: Often 300-800+ feet

Is Deeper Better?

Advantages of Deeper Wells

• Better protected from surface contamination
• More stable water level during drought
• Often better water quality
• Less affected by seasonal variation
• Less affected by neighbor's pumping

Disadvantages of Deeper Wells

• Higher drilling cost ($15-$50+ per foot)
• More expensive pump needed
• Higher electricity costs to lift water
• More difficult/expensive to service
• Deeper doesn't guarantee more water

The Bottom Line

Deeper is not always better—it depends on geology. The goal is to reach a productive aquifer with reliable, quality water. Sometimes that's at 150 feet; sometimes it requires 400+ feet.

How Depth Affects Cost

Drilling Costs

• Typical cost: $15-$50 per foot (varies by geology)
• 100-foot well: $1,500-$5,000 (drilling only)
• 300-foot well: $4,500-$15,000 (drilling only)
• 500-foot well: $7,500-$25,000 (drilling only)

Pump Costs by Depth

Operating Costs

Deeper wells cost more to operate because the pump works harder to lift water. A 500-foot well might cost 2-3× more in electricity than a 150-foot well.

We service all major pump brands including Franklin Electric, Grundfos, Goulds (Xylem), and Sta-Rite (Pentair). Our trucks carry common parts and components for same-day repairs.

Frequently Asked Questions

How deep should a well be?

There's no universal answer—it depends on local geology. The driller goes deep enough to reach a productive aquifer with reliable water. In San Diego County, 100-500 feet is typical.

Is a deeper well better?

Deeper wells are often more reliable and protected from contamination, but they cost more to drill and operate. Deeper doesn't guarantee more water—it depends on hitting productive zones.

How do I find out how deep my well is?

Check your well completion report (filed with county). Or measure with a weighted string. A well professional can also determine depth during service.

What happens if you drill a well too deep?

You spend more money, and the pump costs more to run. In some areas, very deep water may have quality issues (high minerals, salinity). The driller balances depth, water quality, and cost.

Can a well be too shallow?

Yes—shallow wells are vulnerable to surface contamination, may go dry during drought, and may not meet regulatory requirements. Minimum depths are often required by permit.