A drilled hole becomes a safe water well through its completion: the casing, the seal around it, the screen at the bottom where needed, and the fittings at the top. These parts are mostly invisible once the job is done, so it pays to understand them before you sign a contract and to check the visible parts when the work is finished.
What are the parts of a completed well?
| Component | What it does | What to get in writing |
|---|---|---|
| Casing | Keeps the hole open; with grout, keeps out dirt, surface water and lower-quality groundwater | Material, diameter, wall thickness, length |
| Grout (annular seal) | Seals the gap between the drilled hole and the casing | Material and how it is placed |
| Screen | Lets water in while limiting sediment, where the formation needs it | Whether a screen is needed, type and length |
| Pitless adapter | Lets the water line exit underground below the frost line with a sanitary seal | Type and depth |
| Well cap | Keeps out debris, insects and small animals; vents air | Type of cap or seal |
The U.S. Environmental Protection Agency describes casing as a tube that keeps the well open and, with grout, keeps out dirt, excess water and lower-quality groundwater; common materials are carbon steel, plastic and stainless steel, and some states and localities set minimum casing lengths. It describes the cap as sitting on top of the casing with a vent for pressure, the screen as limiting sediment entry, and the pitless adapter as keeping the water pipe below the frost line with a sanitary, frost-proof seal. EPA: Learn About Private Water Wells [EPA-LEARN source note]
What does the grout seal do?
In loose material, a drilled well needs casing and a screen, and the space around the casing must be sealed with grout to prevent contamination. NGWA (Wellowner.org): Types of Wells The National Ground Water Association's contract guidelines list the casing diameter and thickness, the grouting, the type of cap or seal and the type of screen among the items to specify. NGWA: Guidelines for Written Contracts [NGWA-TYPES source note] [NGWA-CONTRACT source note]
How deep does well casing go?
Casing depth depends on the geology and on local code. Guidance for inspectors says casing depth should meet state and local codes and, where none apply, extend at least 50 feet below the surface. Water Systems Council: wellcare Guide to Evaluating Water Wells (for home inspectors) The well log should record the actual casing depth; see how to read a water well log. [WSC-INSPECTOR source note]
How do you check a finished wellhead?
You can check these items yourself when the job is complete:
- Height: casing at least 12 inches above the ground; in flood-prone areas, one to two feet above the highest recorded flood level. Water Systems Council: wellcare Guide to Evaluating Water Wells (for home inspectors)
- Cap: vermin-proof, watertight and securely attached.
- Grading: soil sloped away so water drains from the wellhead. NGWA's owner checklist says to keep the well top at least a foot above ground and slope the soil for drainage. NGWA (Wellowner.org): Homeowner's Maintenance Checklist
- Paperwork: the well log, the yield test result, the disinfection record and the first water test.
Common casing and wellhead problems
| Problem | Why it matters | What to do |
|---|---|---|
| Casing cut off below grade or buried | Surface water can enter the well | Have a contractor extend the casing above grade |
| Cracked, loose or missing cap | Insects, rodents and debris can get in | Replace with a secure, vermin-proof cap |
| Ground sloping toward the casing | Runoff pools at the wellhead | Regrade so water drains away |
| Settled or cracked surface seal | A path for contamination along the casing | Have a licensed contractor inspect and repair |
| Corroded steel casing | Leaks can admit shallow water | Contractor inspection; possible liner or replacement |
EPA recommends periodically inspecting for cracked, corroded or damaged casing, a broken or missing cap, and settling or cracking of surface seals. EPA: Protect Your Home's Water Any of these is a good reason to test the water too; see private well water testing. [EPA-PROTECT source note]
Questions for your driller about completion
- What casing material, diameter and wall thickness will you use, and how deep?
- What grout material, and how will it be placed?
- Will the well need a screen?
- What pitless adapter and cap will you install?
- How will you develop and disinfect the well, and will I get the well report?
Compare the answers between bidders with the quote checklist.
After completion
Before the well is used for drinking, it should be disinfected and the water tested by a certified lab. Over the life of the well, periodically inspect the casing for cracks or corrosion, the cap for damage, and the surface seal for settling. EPA: Protect Your Home's Water The well maintenance checklist puts those checks on a schedule. [EPA-PROTECT source note]
Common questions
How far should well casing stick out of the ground?
Guidance for home inspectors says at least 12 inches above the land surface, and one to two feet above the highest recorded flood level in flood-prone areas. NGWA's owner checklist also says to keep the well top at least a foot above ground. Local code may set its own figure.
How deep does well casing go?
It depends on geology and local code. Casing typically extends through loose material and into stable formation, and some states set minimum lengths. Where no code applies, one industry guide suggests at least 50 feet below the surface.
Steel or plastic well casing?
Both are common, along with stainless steel. The right choice depends on local code, depth, geology and water chemistry. Ask the driller to state the material, diameter and wall thickness in the contract.
What is a pitless adapter?
A fitting on the casing below the frost line that lets the water line leave the well underground, protected from freezing, while keeping the well sealed against contamination.
Why does the well cap need a vent?
The vent lets air move in and out as the water level changes during pumping. The cap should still keep out insects, small animals and debris, so it should be screened and securely attached.
What is a well cap and why does it matter?
The well cap sits on top of the casing and keeps out debris, insects and small animals while venting air. A cracked or loose cap is a common way contamination enters a well, so it should be watertight, vermin-proof and securely attached.
Sources & claim context
Citations mark where guidance is grounded. They are general resources dated on retrieval, not guarantees for any property, project, price, licensure, permit or yield. No expert, attorney or reviewer signoff is claimed by this site.
EPA: Private Wells · EPA · accessed 2026-10-10
https://www.epa.gov/privatewells
Does not specify local testing/permit rules or guarantee safety
EPA: Protect Your Home's Water · EPA · accessed 2026-10-10
https://www.epa.gov/privatewells/protect-your-homes-water
No setback distances or local rules; owners responsible for private wells
EPA: Learn About Private Water Wells · EPA · accessed 2026-10-10
https://www.epa.gov/privatewells/learn-about-private-water-wells
Typical depths are general descriptions, not local requirements
NGWA (Wellowner.org): Homeowner's Maintenance Checklist · NGWA · accessed 2026-10-10
https://wellowner.org/resources/water-well-maintenance/homeowners-well-maintenance-checklist/
Industry guidance; local code governs construction
NGWA (Wellowner.org): Types of Wells · NGWA · accessed 2026-10-10
https://wellowner.org/resources/basics/types-of-wells/
General descriptions; local code may prohibit some types
NGWA (Wellowner.org): Guidelines for Written Contracts · NGWA · accessed 2026-10-10
https://wellowner.org/basics/planning-for-a-water-well/guidelines-for-written-contracts/
Does not prescribe who pays for a dry hole
Water Systems Council: wellcare Guide to Evaluating Water Wells (for home inspectors) · Water Systems Council (wellcare) · accessed 2026-10-10
Guideline distances are not legal requirements; check state rules on who may inspect
Claims are grounded in the dated source notes above; project-specific price, yield, licensure and permit answers require site-specific and local verification.