A licensed well driller will not quote you a single depth over the phone, and that is not evasiveness. Well depth is decided almost entirely by local geology, not by a rule of thumb, and two houses on the same street can end up with wells that differ by hundreds of feet. The real question is not how deep a well should be in general. It is what determines depth on your specific property, what your state actually requires near the surface regardless of total depth, and how to find out both before a drill rig shows up.
Table Of Contents
−- The Three Well Types and Their Real Depth Ranges
- What Actually Decides How Deep Your Well Needs to Go
- Why State Codes Set a Casing and Grouting Minimum, Not a Total Depth
- What Drilling to That Depth Actually Costs
- How to Find Your Actual Number Before the Rig Shows Up
- Depth Does Not Predict What Is in Your Water
The Three Well Types and Their Real Depth Ranges
The EPA groups private wells into three broad construction types, and depth is built into the category itself. Dug or bored wells run roughly 10 to 30 feet, driven wells run roughly 30 to 50 feet, and drilled wells can reach a few hundred feet or, in some geology, several thousand. Almost every new residential well today is drilled, since the older dug and bored methods sit too close to the surface to meet most state contamination setbacks. That single fact already answers the vague version of the question. A modern well is not shallow by design. How deep the drilled hole actually needs to go is a separate matter entirely, and it comes down to what is under your specific lot.
What Actually Decides How Deep Your Well Needs to Go
A driller has to reach an aquifer that will actually hold up, not just the first trace of moisture in the soil. That means drilling below the lowest seasonal water table, then adding a buffer below that for drawdown, the drop in water level that happens every time the pump runs. Skip the buffer and a well that tested fine in a wet spring can run the pump dry by late summer. Confined aquifers, sealed under a layer of clay or rock, behave differently from unconfined ones sitting close to the surface, and a driller sizing your well has to know which one they are hitting before they can give you a real number.
Bedrock geology makes this worse in a specific, well documented way. USGS testing in southeastern New Hampshire found arsenic concentrations varying by more than 7 micrograms per liter between wells sitting close together, because each well draws from a different fracture in the same rock formation rather than one uniform underground reservoir. The same logic explains why your neighbor’s well can test clean for uranium while yours does not, and why two wells drilled to a similar depth a few hundred feet apart can come back with completely different hardness, salinity, or mineral content. Depth and water chemistry are decided by two different things.
Why State Codes Set a Casing and Grouting Minimum, Not a Total Depth
No state regulator tells a driller how deep to go, because they cannot know your aquifer in advance. What they do regulate, closely, is the first stretch of the borehole near the surface. New York requires casing to extend at least 19 feet below grade. North Carolina requires at least 20 feet of casing into competent bedrock, or a seal into a confining clay layer for wells drilled through loose soil. Indiana sets its minimum at 25 feet with at least a 5 inch inside diameter. In every case, the annular space between the casing and the borehole wall gets filled with neat cement or bentonite grout from the bottom up, sealing off the shallow zone where bacteria, fertilizer runoff, and septic effluent actually travel. A well can be 400 feet deep and still fail this part of the code if the top 20 feet were not sealed correctly.
Setback distances follow the same logic and vary by state in a narrow band. North Carolina and Indiana both require at least 50 feet between a well and a septic tank, with North Carolina requiring 100 feet to the drain field and New York requiring 100 feet to an absorption field and 150 feet to a seepage pit. Landfills push the setback out to 500 feet in most codes. These are the same contamination pathways that make shallow wells riskier in the first place, and they explain why the casing and grouting rule matters more to your actual safety than the total depth number ever will.
What Drilling to That Depth Actually Costs
Cost scales with depth in a fairly predictable way once a driller is on site, though the range is wide. Drilling alone runs about 20 to 30 dollars per foot, and a fully installed well, casing, screen, and pump included, runs 30 to 80 dollars or more per foot depending on the region and what the rig hits along the way. A 100 foot well typically lands between 3,000 and 8,000 dollars complete. A 200 foot well, close to the national average, runs 6,000 to 16,000 dollars. Go to 300 feet and the range moves to 9,000 to 24,000 dollars, and a 500 foot well can run 15,000 to 40,000 dollars. Hard rock, remote access, or a driller who has to case through unstable ground can push the per foot cost past 100 dollars regardless of the final depth.
How to Find Your Actual Number Before the Rig Shows Up
Asking one neighbor is not a plan, since their well may sit on a different fracture or a different aquifer layer entirely. A better starting point is the National Ground Water Association’s Water Well Map, launched in October 2025 and free to the public through WellOwner.org. It tracks more than 14 million wells nationwide, including depth, construction date, and water quality trend data pulled from actual state well completion records, so you can see what drillers in your specific area have actually hit rather than guessing. A licensed local driller can pull the same completion records for your parcel directly from the state health department in most states, and should be doing that before quoting you a number at all.
Depth Does Not Predict What Is in Your Water
This is the part a depth number cannot tell you. Shallow dug and bored wells, the 10 to 50 foot range, sit closest to the surface contamination pathway, so they carry the highest bacterial and nitrate risk of the three well types. But a deep drilled well is not automatically clean either, since it can still tap a bedrock fracture carrying arsenic, uranium, or high salinity depending on what formation it happens to cross. That is exactly why the CDC recommends testing every private well, shallow or deep, at least once a year for total coliform bacteria, nitrates, TDS, and pH, the same four item baseline the Safe Drinking Water Act never requires because private wells fall outside its reach entirely.
If a test comes back positive for bacteria, nitrate, arsenic, or several dissolved contaminants at once, the fix should match what the test actually found, not how many feet the well goes down. A well confirmed for multiple contaminants at once, rather than one isolated issue, is exactly the situation a whole house reverse osmosis system is built to handle.
Do not go into a drilling quote asking for a specific number of feet. Hire a state licensed driller, let the local water table and the aquifer geology decide the real depth, and hold them to your state’s casing and grouting minimum near the surface no matter how deep the well ultimately runs. Then test the finished well before assuming depth alone bought you safety, because depth decides supply. It does not decide water quality.
Jay
Jay is a health and wellness enthusiast with expertise in water quality and nutrition. As a knowledgeable advocate for holistic well-being, Jay successfully manages Type 2 Diabetes through informed lifestyle choices. Committed to sharing reliable and authoritative insights, Jay combines firsthand experience with a passion for enhancing health."