Well Drilling Terms Explained: A Plain-English Glossary
If you are researching a water well for your Gresham property, you have probably hit words like "static water level" and "casing" without a clear explanation. This well drilling glossary translates the jargon into plain English so you can read a quote line by line, ask sharper questions, and spot when something does not add up. Each entry starts with a one-sentence definition you can use on its own. Bookmark it and pull it up the next time a driller starts talking fast.
- Aquifer: the underground layer that holds your water
- Groundwater: the water itself, down in the ground
- Water table: where the water starts below the surface
- Static water level: how high water sits in a resting well
- Drawdown: how far the level drops when the pump runs
- Well yield: how much water the well can give
- Casing: the pipe that lines the borehole
- Well cap: the lid that keeps contamination out
- Well screen: the filter section that lets water in
- Pitless adapter: the below-ground connection to your house
- Submersible pump: the pump that sits down in the well
- Pressure tank: the tank that stores water under pressure
- Pressure switch: the part that tells the pump when to run
- Borehole: the hole the drill rig makes
- Grouting: sealing the space around the casing
- Well development: cleaning out a new well before use
- Well log: the driller's written record of your well
- Cost per foot: how most drilling quotes are priced
Water Underground: Where Your Well Water Comes From
Most confusion starts below the surface, so this part of the well drilling glossary covers the ground itself.
Aquifer and Well Drilling Basics
An aquifer is an underground layer of rock, sand, or gravel that holds water and lets it flow into a well. Your well is only as good as the aquifer it taps, which is why drillers talk about it so much. In the hills east of Gresham, aquifer depth and quality change from one property to the next, so a neighbor's well tells you something but not everything. If a provider offers an aquifer and well depth assessment before drilling, that is a sign they are planning the well rather than guessing.
Groundwater
Groundwater means water that has soaked into the ground and collected in the spaces within soil and rock. Every private well pulls groundwater; there is no hidden underground river feeding it. Groundwater levels can shift with the seasons, which is why a well that runs strong in winter can slow down in a dry summer. Understanding this helps you ask the right questions about how a proposed well will hold up year round.
Water Table
The water table is the depth below the surface where the ground becomes saturated with water. Above it, the soil is damp at most; below it, the spaces are full. The water table rises and falls with rainfall and season, and it varies from property to property. A driller who talks about your water table is telling you how deep they expect to go before hitting usable water, which directly affects the price of the job.
Static Water Level
The static water level is how high the water sits in your well when the pump has been off long enough for it to settle. Think of it as the well's resting level. It matters because your pump has to sit below it, and a falling static level over the years can mean the well or the aquifer is changing. A well inspection usually includes checking this number, and comparing it to the original well log tells you a lot.
Drawdown
Drawdown is how far the water level in a well drops while the pump is running. Every well draws down some; the question is how far and how fast it recovers. A well with heavy drawdown may need a deeper pump setting, a smaller pump, or in some cases a deeper well. If a provider measures drawdown during a well inspection, they are checking whether the pump and the well are matched to each other.
Well Yield
Well yield is the amount of water a well can produce over time, usually described in gallons per minute. Yield decides whether a well can handle a household, irrigation, or a commercial operation. A low-yield well is not always a dealbreaker, but it changes how the pump system gets designed. Lenders and buyers often ask for a yield test during a sale, so this term shows up in real estate paperwork too.
Parts of the Well and Pump System
Casing
Casing is the steel or plastic pipe that lines the drilled hole and keeps it from collapsing. It also blocks shallow surface water and dirt from getting into your drinking water. When a well drilling quote lists casing by the foot, that is normal; deeper wells need more of it, and that is one of the biggest reasons cost varies. Our guide to well drilling costs walks through how casing and depth drive the total.
Well Cap
A well cap is the sealed cover on top of the casing where it sticks up out of the ground. Its whole job is keeping insects, rodents, and surface water out of your well. A cracked or loose cap is one of the cheapest problems to fix and one of the most common sources of contamination. If well water testing turns up bacteria, the cap is often the first thing a good technician checks.
Well Screen
A well screen is a slotted or perforated section at the bottom of the casing that lets water in while holding sand and gravel back. Wells drilled into sand or gravel usually need one; wells in solid rock often do not. A clogged screen can slowly choke off a well's yield over the years. When someone mentions "rehabilitating" a well, cleaning the screen is often part of that work.
Pitless Adapter
A pitless adapter is the fitting that connects your well to the underground water line running to the house, below the frost line. "Pitless" just means no pit; older wells sometimes had a dug pit around the wellhead, which invited flooding and contamination. It matters during well pump replacement because the pump gets pulled up through this connection. If an older well still uses a well pit, expect a provider to recommend upgrading.
Submersible Pump
A submersible pump is a sealed electric pump that hangs down inside the well, underwater, and pushes water up to your house. Most modern residential wells use one, and it is the part that fails most often after years of service. When people search for well pump repair or well pump replacement, this is usually the piece they mean. A pump that runs but delivers no water may have a failed motor, a broken pipe, or a well that has dropped below the pump, so diagnosis matters before parts get replaced.
Pressure Tank
A pressure tank is the tank, usually in your garage, basement, or well house, that stores water under pressure so the pump does not start every time you open a tap. A failing tank makes the pump switch on and off rapidly, which is called short cycling and which wears the pump out early. Many "bad pump" calls turn out to be a bad tank, which is a cheaper fix. Any honest pump and well repair visit should check the tank before condemning the pump.
Pressure Switch
A pressure switch is the small control that turns the pump on when water pressure drops and off when it recovers. It is a common failure point, and the symptoms, no water or weak pressure, look identical to a dead pump. Because it is one of the least expensive parts in the system, a good technician rules it out first. If your water cuts out entirely, ask whether the switch was tested before agreeing to a full well pump replacement.
The Drilling Process, Paperwork, and Price
Borehole and Well Drilling Operations
A borehole is the hole the drilling rig cuts into the ground before any casing or pump goes in. Its depth and diameter shape the whole project; both are set by the geology and the water use you are planning, whether that is a single home or a commercial well. Since well drilling is priced largely by depth, the borehole is where the money goes. Two wells a mile apart can end up at different depths, which is why quotes usually carry a per-foot rate rather than one flat number.
Grouting
Grouting means filling the gap between the casing and the borehole wall with a sealing material, usually a cement or clay mix. It stops surface water from trickling down the outside of the casing into your drinking water. Grouting is required practice, not an upsell, so seeing it on a quote is a good sign. A well that was never properly grouted can test fine for years and then fail after a wet winter.
Well Development
Well development is the cleanup work done on a new well to flush out drilling debris and open up water flow before the pump is installed. A well that skips development can produce cloudy water and lower yield than it should. It is normal for this to appear as its own line on a quote. If a new well delivers murky water in its first days, ask whether development was completed.
Well Log
A well log is the written record a driller files describing the well: its depth, casing, the layers of soil and rock encountered, and the water found. In Oregon, drillers file these with the state, and you can often look up an existing well's log. For a buyer, the log is the well's birth certificate; a well inspection paired with the original log shows how the well has aged. Ask for a copy whenever a new well is drilled on your property.
Cost per Foot
Cost per foot is the standard way drilling gets priced: a set rate for every foot of depth, plus casing and other materials. It exists because nobody can promise the exact depth where your property hits reliable water. This is why two honest quotes can differ, and why a suspiciously low flat price deserves questions about what happens if the well runs deep. Get the per-foot rate, the casing rate, and the estimated depth range in writing, then compare quotes on those numbers rather than the bottom line alone.
Using These Terms
That is the vocabulary behind most quotes, inspection reports, and phone calls in this trade. What this well drilling glossary gives you is the ability to read an estimate line by line, ask why a number is there, and understand the answer you get back. When a provider explains your well in these terms and you can follow along, you are in a much stronger spot to make the right call for your property.
If you need well drilling, Clackamas Well Drilling can help.
Prefer to talk it through? Call (503) 782-5215 — a quick call is usually the fastest way to get a straight answer for your situation.
