800-Foot Well Drilling Cost

The 800-foot residential well: why it exists

Eight hundred feet is rarely a "natural" residential drilling depth. The geological aquifers that produce residential water are usually closer to the surface; an 800-foot well exists either because the local water table has dropped catastrophically over decades, or because the shallower aquifers were over-pumped and the homeowner is now reaching deeper, slower-recharging aquifers below.

The central Arizona Active Management Areas (ADWR-regulated zones in Pinal, Cochise, Pima, Maricopa) are the textbook case. The Salt River Valley alluvial aquifer that supplied agricultural and residential demand from 1900 through the 1970s had a static water level of 100 to 200 feet below ground. Sixty years of agricultural and municipal pumping (often at rates 5 to 10 times the natural recharge) drove the water level down to 400 to 700 feet in many sub-basins. New residential wells in these areas now routinely reach 700 to 900 feet to find productive water, and the cost reflects the depth. Per ADWR Active Management Area documentation, exempt-well thresholds (35 gpm) and permit requirements are particularly demanding in these sub-basins.

Similar dynamics exist in parts of Nevada, the Texas Panhandle and the Ogallala-overlying Plains. The unifying theme is decadal water-table decline. A 1980 well at 400 feet may still produce water in 2026 but at reduced volume; new wells in the same area are 700+ feet because that is where productive water now sits.

Cost breakdown for a representative bid

Take an 800-foot well in Pinal County, Arizona, drilled through 80 feet of caliche-cemented alluvium, 320 feet of basin-fill sediments, and 400 feet of older Tertiary fanglomerate to reach a confined aquifer. Eight-inch steel casing is set 800 feet (the full bore is cased because alluvial sediments and basin-fill collapse without support). A perforated stainless-steel well screen is placed across the 100-foot productive zone at the bottom. A 5 HP submersible pump is set at 780 feet on stainless drop pipe. A 119-gallon pressure tank is in a heated well-house.

Line items at 2026 rates. Mobilisation $2,000 (specialised deep-well rig). Drilling 80 feet through caliche-cemented alluvium at $42 per foot ($3,360). Drilling 320 feet through basin-fill at $38 per foot ($12,160). Drilling 400 feet through fanglomerate at $52 per foot ($20,800). Eight-inch steel casing 800 feet at $22 per foot installed ($17,600). Stainless well screen 100 feet at $80 per foot ($8,000). Gravel pack around screen, $1,200. Grouting 80 feet, $1,200. Well cap with sanitary seal, $400. Development 16 hours, $2,000. Submersible pump 5 HP with control box, $5,500. Stainless drop pipe 780 feet at $11 per foot ($8,580). Submersible cable 780 feet (6 AWG for 5 HP), $3,100. Pressure tank 119 gallon, $1,600. Well-house with heat and electrical, $4,500. Trench from well-house to residence 400 feet, $1,800. ADWR permit and water test $700. Subtotal: $94,500. With 10 percent contingency, $103,950. That is a typical upper bid for deep central-AZ residential drilling in 2026.

Drilling alone ($36,320) is 38 percent of subtotal. Casing-and-screen ($26,800) is 28 percent (because the full 800 feet must be cased in unconsolidated alluvium, very different from hard-rock geology where casing is minimal). Pump-and-electrical-and-tank package ($18,780) is 20 percent. Well-house and trench ($6,300) is 7 percent. Everything else (mobilisation, development, permit, contingency) is 7 percent. The casing share is unusual because the full-bore casing dramatically changes the cost profile compared to bedrock wells of similar depth.

Why full-bore casing changes the economics

An 800-foot bedrock well in granite would have very different economics than the Arizona alluvial example above. In hard-rock geology, only the upper 40 to 100 feet would be cased (through the weathered zone) and the remaining 700+ feet would be open bore. The casing line item drops from $26,800 to perhaps $2,000, but the drilling line item climbs because hard-rock per-foot rates are higher. The net is that a granite 800-foot well in New Hampshire would cost somewhat less than the Arizona alluvial example overall, even though the per-foot drilling rate is higher.

This is why the geology question dominates everything at deep depths. The same headline "800-foot well" can cost $30,000 in fortunate geology or $80,000 in less fortunate geology, with the difference driven by how much of the bore needs structural support (casing) and how much can stand open in solid rock.

The state well-log databases are again the best way to predict which scenario applies to a given lot. ADWR, NV State Engineer, NM OSE, TX TWDB, OK OWRB and CO DWR all publish searchable databases of historical well completions. The completion record for nearby wells typically includes the casing depth, screen depth, completion technique and (sometimes) the yield. A 30-minute search through the database is the best $0 investment in scoping a deep-well project.

Pump and electrical at 800 feet

Three to five horsepower is the working pump-size range at 800 feet, depending on yield, household size and tank configuration. A 3 HP pump can lift water from 800 feet at low flow rates (3 to 5 gpm); 5 HP supports a normal 4 to 6 person household at 12 to 18 gpm peak demand. Most installers in deep-well markets spec 5 HP for new installs and accept the slightly higher electricity cost in exchange for the longer pump life from reduced cycling.

The electrical service for a 5 HP submersible at 800 feet is a real consideration. The pump motor draws 23 to 28 amps at 230V running, and 100+ amps for the first 0.5 to 1 second at start-up. The submersible cable must be sized to keep voltage drop within NEC limits at start-up; 6 AWG is the standard for 5 HP at this depth. Cable runs $4 to $5 per foot installed. The 780-foot run is $3,000 to $4,000. The home's electrical panel typically needs a dedicated 50A breaker for the well, often requiring a service upgrade if the existing panel is 100A residential.

Drop pipe at 800 feet is exclusively stainless or schedule-160 galvanized; PVC and schedule-80 galvanized are below their safety margins. Stainless drop pipe at 780 feet weighs roughly 1,200 to 1,500 pounds dry, plus another 600 pounds of water in the column when the pump is running. The pitless adapter and surface support hardware must be sized for this load with comfortable safety margins. Drillers in deep-well markets typically use a load-rated cable suspension instead of (or in addition to) drop-pipe support to reduce the stress on the pipe couplings.

Pump replacement economics

At 800 feet, pump replacement is a multi-day operation requiring a specialised pump truck with a 60 to 100-foot mast, two or three workers, and rented equipment if the local driller's standard truck cannot reach the depth. Labour alone runs $2,500 to $4,500 for the pull and re-set. Replacement pump (typically 5 HP) plus controls runs $2,500 to $4,500. New drop pipe (replaced whenever the pump is replaced because the existing pipe's threaded couplings have been under load for 10 to 15 years) runs $3,500 to $7,000. Cable replacement is similarly $2,500 to $4,000. Total pump-out, pump-in cost: $11,000 to $20,000.

This is a meaningful operating-cost line item over the well's life. A 30-year service life with two pump replacements is $22,000 to $40,000 in scheduled maintenance. The math favours larger pressure tanks at install time (less cycling, longer pump life), conservative pump sizing (longer service interval), and stainless drop pipe (longer service life on the pipe component). The cost savings on a single deferred pump replacement easily justifies the install-time premium for premium components.

When 800-foot wells are not the right answer

For homeowners who have not yet drilled, the 800-foot bid is the right time to seriously model alternatives:

Municipal water connection, where available. Often $3,000 to $15,000 for the connection plus $40 to $100 per month operating cost. Over 30 years, $20,000 to $50,000 total. Compares favourably to an $80,000 well plus $30,000 in pump replacements. The blocking question is availability: in most regions where 800-foot wells are needed, municipal water is not present.

Storage cistern with water hauling. A 10,000-gallon underground cistern installed costs $12,000 to $25,000. Hauled water at $150 to $250 per 1,000 gallons delivered, with 14-day refill for a 4-person household, costs $4,000 to $6,500 per year. Over 30 years, $130,000 to $220,000 total. Higher than well, but no capital risk on a dry hole and predictable cash flow.

Shared well with a neighbour. If a neighbouring property has a productive well within 1,000 feet, a shared-well agreement plus a service line ($5,000 to $15,000 for the trench, line and metering) can avoid drilling entirely. The legal complications (water-rights, maintenance liability, easement) are non-trivial and require a real-estate attorney to structure.

Solar-pumped cistern from a low-yield existing well. If an existing well produces 0.5 to 1 gpm, a solar pump at $2,500 to $6,000 can pump continuously into a cistern, providing 700 to 1,400 gallons per day with no electrical service required. The total system (solar pump, controller, batteries, cistern) runs $15,000 to $30,000 and is essentially zero operating cost. Works in remote off-grid scenarios where electrical service to a deep pump is itself a major cost.

Cross-references and adjacent depths

For the per-foot rate, well drilling cost per foot 2026. Shallower bracket, 600-foot well drilling cost. For the Arizona-specific context that dominates this depth bracket, Arizona well drilling cost. For California's deep-Central-Valley analogue, California well drilling cost. For the casing-cost calculation that dominates Arizona-style alluvial deep wells, well casing cost. For the pump and drop-pipe details, pump installation costs.