Water Well Drilling: How It Works

Drilled, driven or dug

Not every well is drilled. EPA describes three types:

Drilled wells are the standard for new homes, and for good reason. CDC says it's generally easier to keep germs and chemicals out of a drilled well than a dug or driven one. EPA notes driven wells draw from shallow water and can be contaminated easily. A driven point well still makes sense for a cabin or a garden spigot in sandy ground with a high water table, but it's a poor choice for a family's drinking water.

How the job goes

1. Site and permit. The well has to sit away from things that can pollute it. CDC lists 50 feet from septic tanks, drain fields and livestock yards, 100 feet from petroleum tanks and stored fertilizer, and 250 feet from manure stacks. Your state may set different numbers. Many states also want paperwork before drilling; Minnesota, for example, requires a notification and fee to the health department before work starts.
2. Drilling. The rig bores down, bringing up cuttings that tell the driller what rock and soil they're passing through. They keep going until they hit a layer that gives enough water.
3. Casing and grout. Casing keeps the hole open and keeps surface water out. Household casing is typically 4 to 6 inches across. Minnesota requires watertight casing at least 15 feet below the surface, with grout pumped in from the bottom up through a tremie pipe rather than poured from the top.
4. Screen and development. In sand and gravel, a screen at the bottom keeps sediment out, usually 3 to 5 feet long on a home well. The driller then pumps the well to clear fines and see how much water it gives. Our page on well yield and recovery rate covers that test.
5. Pump, pitless adapter and tank. The water line leaves the casing through a pitless adapter below the frost line, and the pump, wiring and pressure tank are installed.
6. Disinfection and testing. Minnesota's handbook says every new well must be disinfected after drilling, before the water is used for drinking or cooking. Contractors there must have the water tested for bacteria, nitrate and arsenic by a certified lab and send the results to the owner. Wherever you live, ask for a test from a state-certified lab before anyone drinks the water.
7. The well record. The driller files a construction record with the depth, water level, geology and pump details. Keep your copy with the deed. You'll want it for every repair from here on.

How deep, and how long it takes

HomeGuide says residential wells average 100 to 300 feet deep. A USGS study found a median depth of 142 feet for domestic wells across the lower 48 states. Your driller can't promise a depth before drilling, but neighbors' well records are the best predictor. See how deep a water well is for how to look those up.

On time: 1 to 3 days of drilling, then pump and electrical work, adds up to roughly a week for most jobs.

Can you drill your own well?

Sometimes, legally. HomeGuide notes that some states allow owners to drill on their own land but still require permits and inspections. Minnesota allows a person to build a well for personal use on land they own or lease, as long as it meets state rules.

Practically, a homeowner can drive a shallow sand point. A drilled, cased and grouted well to a safe depth takes a rig, and a bad grout job can let surface water into the aquifer for decades. We'd hire a licensed driller.

What it costs

HomeGuide's national average for a complete residential well is $10,500. Drilling alone runs $20 to $30 per foot, and $30 to $80 or more per foot with the pump, tank and wiring included. The full breakdown is on our well drilling cost page.

Before the rig shows up

• Mark the septic tank, drain field, buried lines and any fuel tank so the driller can respect the setbacks.
• Make sure a heavy truck can reach the spot without crossing the septic field.
• Ask whether the quote includes the pump, pressure tank, trenching and electrical. HomeGuide warns that those parts aren't always in the per-foot price.
• Put the well as close to the house as the setbacks allow. Longer water and electrical runs cost more.