Well Inspection Terms Explained: A Plain-English Glossary
If you're buying a home on a private well around Gresham, Sandy, Boring, or Damascus, the inspection report and the quotes that follow can read like a foreign language. This well inspection glossary translates the terms you'll actually see, so you can read a quote line by line, ask sharper questions, and spot a problem before it costs you. Each entry starts with a plain definition you can understand in one read. No jargon left unexplained, no sales pitch.
- Wellhead: the top of the well you can see
- Well Casing: the pipe that lines the hole
- Well Cap: the lid that keeps stuff out
- Pitless Adapter: the underground water connection
- Aquifer: the underground water layer
- Static Water Level: how high the water sits at rest
- Drawdown: how far the water drops when pumping
- Flow Test: measuring how much water the well gives
- Recovery Rate: how fast the well refills
- Submersible Pump: the pump that sits down in the well
- Pressure Tank: the tank that stores water under pressure
- Pressure Switch: the part that turns the pump on and off
- Check Valve: the one-way gate that holds water in the line
- Well Yield: the well's usable output
- Water Quality Testing: lab checks on what's in the water
- Coliform Bacteria: the standard bacteria screen
- Well Log: the well's birth certificate
- Shock Chlorination: a one-time disinfecting treatment
Parts of the Well You Can See (and the Parts You Can't)
Most of a water well is hidden underground, which is exactly why the visible parts get so much attention during a well inspection. Here is what the inspector is looking at, top to bottom.
Wellhead Components in Your Well Inspection Glossary
The wellhead is the visible top of your well, usually a steel pipe sticking a foot or two out of the ground with a cap on it. An inspector checks that it stands high enough above grade, that the ground slopes away from it, and that nothing is cracked or loose. A wellhead sitting in a low spot where rainwater pools is a red flag, because surface water can carry bacteria down into your well water. If a quote mentions "raising the wellhead" or "regrading," that is what they are fixing.
Well Casing
Well casing is the pipe, usually steel or PVC, that lines the drilled hole and keeps the walls from caving in. It also keeps shallow, dirty surface water out of the deeper, cleaner groundwater your pump draws from. A cracked or rusted-through casing is a serious finding because it can let contamination in. Casing repairs vary in scope, so ask the provider exactly what section is damaged and how they plan to fix it.
Well Cap
A well cap is the lid that seals the top of the casing and keeps insects, rodents, and debris out of your well. Modern caps are vermin-proof and vented so the well can breathe without letting anything crawl in. A missing, cracked, or loose cap is one of the cheapest problems to fix and one of the most common findings on older wells. If your report flags the cap, that is usually good news, not bad.
Pitless Adapter
A pitless adapter is the fitting, buried below the frost line, that carries water from the well casing to the pipe running to your house. It lets the water line exit underground so it never freezes, without needing a pit around the well. Leaks at the pitless adapter are a common cause of pressure loss and soggy ground near the wellhead. Repairing one means pulling equipment, so expect it to be a bigger line item than a cap or switch.
Water Supply and Performance Terms
These terms describe how much water your well produces and how reliably it produces it. They matter most when you are comparing properties or deciding whether a well can keep up with your household. Understanding water supply performance is a key part of any well inspection glossary for homeowners.
Aquifer and Well Inspection Glossary Basics
An aquifer is an underground layer of water-bearing rock, sand, or gravel that your well draws from. Think of it as a saturated sponge, not an underground lake. The depth and character of the aquifer under your property drive most of the cost of well drilling, which is why an aquifer and well depth assessment often comes before drilling a new well. Aquifer conditions vary from one property to the next, even between neighbors.
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 things to settle. It is the starting line for measuring performance. Inspectors compare it against past records when those exist, because a falling static level over the years can point to a declining aquifer or a well nearing the end of its useful life.
Drawdown
Drawdown is how far the water level in the well drops while the pump is running. Every well draws down to some degree, but heavy drawdown that never levels off means the pump is pulling water faster than the aquifer can supply it. That is the kind of finding that shapes advice about pump sizing, irrigation habits, or deepening the well.
Flow Test
A flow test measures how many gallons per minute a well can deliver over a sustained period, not just a quick burst. It is the single most useful performance check in a well inspection, and lenders often require one before approving a loan on a well-supplied home. A short test can flatter a weak well, so ask how long the provider runs theirs. Flow testing time is one of the factors covered in our guide to the cost of a well inspection.
Recovery Rate
Recovery rate is how quickly the water level in a well climbs back up after pumping stops. A well with a slow flow but a strong recovery can still serve a household fine with the right storage setup. A well that recovers slowly after a hard draw is the one that runs dry mid-shower. This number tells you how the well behaves in real life, not just on paper.
Well Yield
Well yield is the amount of water a well can reliably produce, usually stated in gallons per minute. Yield is what a buyer's lender, and your future self doing laundry while the sprinklers run, actually cares about. If a seller quotes a yield number from the original drilling decades ago, treat it as history, not a promise. A current flow test is the only honest measure.
Pump and Pressure System Terms
The pump system is where most well problems, and most well pump repair calls, actually happen. These are the parts you will see named on a repair quote.
Submersible Pump
A submersible pump is a sealed electric pump that sits down inside the well, underwater, and pushes water up to your house. It is the most common setup for residential wells in this area. Because it lives at the bottom of the well, diagnosing and replacing one means pulling it up on its pipe and wire, which is why well pump replacement costs more in labor than the swap of an above-ground part. If your water stops entirely, the submersible pump is one of the first suspects.
Pressure Tank
A pressure tank is the storage tank, usually in your garage, basement, or well house, that holds water under air pressure so the pump does not have to start every time you open a tap. Inside is a rubber bladder separating air from water. When the bladder fails, the pump starts and stops in fast bursts, called short cycling, which wears the pump out early. A failing pressure tank is a routine well and pump repair; ignoring it can turn into a full pump replacement.
Pressure Switch
A pressure switch is the small control that senses water pressure and tells the pump when to turn on and off. It is a common failure point and one of the least expensive parts in the whole system. If your water cuts out and then comes back, or the pump will not start at all, a technician often checks the pressure switch before anything else. Hearing "it might just be the switch" from a provider is usually the best-case diagnosis.
Check Valve
A check valve is a one-way gate in the water line that keeps water from draining back down into the well when the pump shuts off. When one fails, the system loses pressure between uses and the pump has to work harder, cycling more than it should. A bad check valve on its own is a modest repair, but the extra pump wear it causes is the real cost of leaving it alone.
Water Quality, Testing, and Glossary Resources
Water Quality Testing
Water quality testing means sending a sample of your well water to a lab to check for bacteria, nitrates, and other contaminants. Well water is not treated by a city utility, so testing is the only way to know what is in it. Real estate transactions in well country usually require at least a bacteria and nitrate test. Well water testing is a separate service from the mechanical inspection, so confirm whether a quote includes it or lists it as an add-on.
Coliform Bacteria
Coliform bacteria are a family of common bacteria that labs use as the standard indicator of well contamination. Most coliforms are harmless by themselves, but their presence means surface water or waste is finding a path into your well. A positive coliform result is not a reason to panic; it is a reason to find the entry point, often a bad cap or shallow casing issue, and then disinfect.
Well Log
A well log is the record filed when a well was drilled, showing its depth, casing details, the soil and rock layers found, and the yield measured at the time. Think of it as the well's birth certificate. Oregon keeps these records on file, and a good provider will pull the log before quoting work, because it tells them what they are dealing with before anything comes out of the ground. If no log exists for an older well, expect more uncertainty in any estimate.
Shock Chlorination
Shock chlorination is a one-time disinfection where a strong chlorine solution is put into the well and plumbing, left to sit, and then flushed out. It is the standard follow-up after a positive bacteria test, a repair that opened the system, or new well installation. It kills the bacteria present that day; it does not fix the pathway that let them in. If a provider recommends shock chlorination without addressing a bad cap or casing problem, ask what stops the bacteria from coming back.
Using These Terms
That is the vocabulary this well inspection glossary set out to hand you: enough to read a report without guessing and to ask a provider what a finding actually means for your water and your wallet. When a quote lists "pitless adapter leak" or "short cycling at the pressure tank," you now know whether you are looking at a small part or a pulled pump. Good providers welcome those questions, and clear answers are how you tell them apart.
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.
