Getting your home’s water tested can feel a bit like getting lab work done at the doctor: you know it’s important, but the results can look like a foreign language. Numbers, abbreviations, “ND,” “mg/L,” “pCi/L,” and sometimes a note that says “action recommended.” So what do water test results actually mean for your family, your plumbing, and your peace of mind?

This guide walks through the most common things you’ll see on a water report—what they are, why they matter, what typical sources look like, and what homeowners usually do next. Whether you’re on a private well in New Hampshire or connected to a town supply, learning to read your results helps you make smarter choices (and avoid spending money on the wrong fix).

We’ll keep things practical: how to interpret units, what “safe” really means, why you might see seasonal changes, and how to prioritize next steps if multiple contaminants show up at once.

How to read a water test report without getting overwhelmed

Most water reports are built like a spreadsheet: contaminant name, your result, the lab’s detection limit, and a guideline or standard. The tricky part is that different contaminants use different units and different standards. Some have a strict legal limit (especially for public water systems), while others have a health advisory or an aesthetic guideline (taste, odor, staining).

Start by identifying your water source on the report. Private wells typically use health-based guidelines (like EPA health advisories) and state recommendations, while municipal water often references federal Maximum Contaminant Levels (MCLs). If your report doesn’t clearly say “well” or “municipal,” look for clues like “total coliform” screening (common for wells) or “chlorine residual” (common for municipal).

Next, look for flags like “above MCL,” “exceeds action level,” or “recommended follow-up.” Those are your priority items. After that, focus on contaminants that may not exceed a limit but still cause real-world issues—like hardness, iron, manganese, or low pH—because they can damage fixtures and shorten appliance life over time.

Units you’ll see all the time: mg/L, µg/L, ppm, ppb

mg/L (milligrams per liter) is essentially the same as ppm (parts per million) in water. So if you see nitrate at 5 mg/L, that’s basically 5 ppm.

µg/L (micrograms per liter) is essentially the same as ppb (parts per billion). It’s a smaller unit used for contaminants that matter at very low levels—like arsenic, lead, PFAS, and many pesticides.

A quick conversion that helps: 1 mg/L = 1,000 µg/L. If your arsenic is 8 µg/L, that’s 0.008 mg/L. Same number, different scale.

“ND,” detection limits, and why “not detected” isn’t always “zero”

ND means “not detected,” which sounds like “none,” but it really means the lab didn’t detect it above the method’s detection threshold. Every test has a minimum level it can reliably see, often listed as MDL (method detection limit) or RL (reporting limit).

For example, if PFAS is listed as ND with an RL of 2 ng/L, the lab is saying “if PFAS is present, it’s below 2 ng/L.” That’s still useful information, especially when you compare results over time or between labs.

If you’re tracking a known issue—like arsenic in a region where it’s common—ask whether the lab’s reporting limit is low enough to be meaningful for your decision-making. Sometimes paying a little more for a more sensitive method is worth it.

Microbiological results: bacteria, “coliform,” and what to do right away

Microbiological results are the ones you don’t want to ignore, because they can point to immediate health risks. The most common screening tests for wells are total coliform and E. coli. Coliform bacteria aren’t always harmful themselves, but they can indicate that surface water or contamination pathways are reaching your well.

Municipal water is disinfected and monitored on a schedule, but wells are “owner-managed,” meaning you’re the one responsible for testing and maintenance. If you see a positive bacteria result, treat it as a “stop and investigate” moment.

One important nuance: bacteria results can change quickly. A heavy rain, spring snowmelt, a cracked well cap, or even recent plumbing work can shift results. That’s why follow-up sampling is often recommended after any corrective action.

Total coliform vs. E. coli: the difference that matters

Total coliform is a broad group. A positive result suggests your well system may be vulnerable—think improper well cap, shallow casing, poor grading around the well, or a pathway for insects and small animals. It’s a sign to inspect the wellhead and consider a resample.

E. coli is more serious because it indicates fecal contamination. If E. coli is present, many homeowners switch to bottled water for drinking/cooking until the source is identified and addressed, then retest to confirm it’s resolved.

Even if you feel fine, don’t assume it’s harmless. Some people are more sensitive than others, and waterborne illness can be especially risky for kids, older adults, and anyone with a compromised immune system.

Common causes of bacteria in well water

Some of the most common causes are surprisingly fixable: a missing or cracked sanitary well cap, a vent screen that’s damaged, or poor drainage that allows puddling around the well casing. Wells should be graded so water flows away, not toward the casing.

Another common cause is plumbing cross-connections or backflow events—like a hose sitting in a bucket of dirty water with no vacuum breaker. If you’ve recently installed irrigation or a new appliance, that’s worth checking.

Sometimes bacteria points to a bigger issue: a compromised well casing, shallow well construction, or nearby contamination sources. If positives repeat, it’s time to look beyond a simple shock chlorination and consider a long-term disinfection approach.

Metals and minerals: the ones that stain, taste weird, or raise health questions

Metals and minerals are a huge category on water reports. Some are mostly aesthetic (like iron staining), while others have health-based limits (like arsenic or lead). Many are naturally occurring in New Hampshire geology, which is why well owners often see them even when there’s no obvious “pollution source.”

What makes metals tricky is that they can vary depending on the water chemistry. Low pH (acidic water) can dissolve metals from pipes. High iron can appear suddenly if well conditions change. And some metals show up as “total” vs. “dissolved,” which can affect treatment choices.

If you’re trying to prioritize, focus first on health-based contaminants (arsenic, lead, uranium, manganese at higher levels), then on corrosivity factors (pH, alkalinity), and then on nuisance issues (iron, hardness) that impact your home.

Arsenic: common in bedrock wells and easy to misinterpret

Arsenic is a naturally occurring element that shows up in many bedrock wells in New England. It’s measured in µg/L (ppb). The EPA MCL for public water systems is 10 µg/L, and many homeowners use that as a benchmark even for private wells.

Arsenic doesn’t have a taste or smell, so the only way to know is testing. Results can also fluctuate depending on well use, seasonal water table changes, and sampling methods. If you’re near the guideline, retesting can help confirm whether you’re consistently above, consistently below, or bouncing around.

Treatment depends on the form of arsenic (As(III) vs As(V)) and the overall water chemistry. That’s why a good test panel often includes supporting parameters like pH, iron, manganese, sulfate, and sometimes speciation if needed.

Lead and copper: often a plumbing story, not a groundwater story

Lead in drinking water is frequently tied to plumbing materials—older solder, brass fixtures, or lead service lines—rather than the aquifer itself. Copper can also leach from pipes, especially when water is acidic or low in alkalinity.

If your report includes “first-draw” and “flushed” samples, that’s a clue the test is trying to separate plumbing contribution from source water. High first-draw and low flushed often points to household plumbing.

For homeowners, the practical next step is usually twofold: address corrosivity (pH/alkalinity) and consider point-of-use filtration for drinking water, especially if you have young children or are pregnant.

Iron and manganese: not always dangerous, but always annoying

Iron can cause reddish-brown staining in sinks and tubs, and it can make water taste metallic. Manganese can cause black staining and may also impact taste. Both can foul appliances, clog aerators, and create slime-like buildup when iron bacteria are involved.

Even when levels are below health guidelines, homeowners often treat iron and manganese because the day-to-day hassle is real: ruined laundry, stained grout, and constant cleaning. If you’re seeing staining but your test shows low numbers, consider whether the sample captured the worst-case conditions (like after the well sits overnight).

Treatment varies by form (dissolved vs particulate) and by water chemistry. Oxidation/filtration, specialized media, or water softening can all play a role, but the right approach depends on your exact results.

Nutrients and agricultural indicators: nitrates, nitrites, and what they imply

Nitrates and nitrites are especially important for homes near septic systems, agricultural areas, or where surface water can influence the well. These are measured in mg/L (ppm). The health concern is strongest for infants, because elevated nitrate can reduce oxygen delivery in the blood (“blue baby syndrome”).

Unlike some naturally occurring metals, nitrates are often a sign of human activity—fertilizer, animal waste, septic leach fields, or stormwater runoff. That doesn’t mean someone is “at fault,” but it does mean you should think about land use and well protection.

Nitrate levels can rise after heavy rain or seasonal runoff. If you test once and get a borderline result, retesting in a different season can help you understand your true risk profile.

Nitrate vs. nitrite: why labs list both

Nitrate (NO3) is the more common form in groundwater. Nitrite (NO2) is usually present at much lower levels because it converts to nitrate in oxygen-rich environments. Labs often test both because nitrite can indicate more recent contamination or different chemical conditions.

The EPA MCL for nitrate (as nitrogen) is 10 mg/L, and for nitrite (as nitrogen) is 1 mg/L in public systems. Your report may list “nitrate as N” or “nitrate as NO3,” which are different expressions—so be sure you’re comparing apples to apples.

If you’re unsure, ask the lab or a water professional to clarify the units and the basis (as N vs as NO3). That single detail can change how you interpret the number.

When nitrates show up: well location and maintenance checks

If nitrates are elevated, start with the basics: is the well properly sealed and above grade? Is the cap sanitary and intact? Is runoff directed away from the casing? Are there any nearby sources like a septic system, livestock area, or fertilizer storage?

It’s also worth reviewing well depth and construction. Shallow wells and dug wells are generally more vulnerable to surface influence than deeper drilled wells. That doesn’t mean a drilled well is immune, but construction matters.

Because nitrates are colorless and odorless, testing is your early warning system. Many homeowners include nitrate testing annually, especially if they have young children in the home.

Chemicals you can’t see: PFAS, VOCs, pesticides, and why screening matters

Modern water testing often includes synthetic chemicals that weren’t on homeowners’ radar years ago. PFAS (“forever chemicals”), VOCs (volatile organic compounds), and pesticide residues can show up even when water looks perfectly clear and tastes fine.

Not every home needs every test every year, but it helps to understand what these categories mean and when they’re most relevant. If you live near certain land uses—industrial sites, airports, fire training areas, landfills, or heavy agricultural operations—screening can be a smart move.

These results can also be emotionally stressful because the names are unfamiliar and the numbers are tiny. The key is to focus on the applicable guideline, confirm the lab method, and then choose treatment based on the specific chemical group.

PFAS: tiny numbers, big attention

PFAS are a family of chemicals used in many products (nonstick coatings, stain repellents, firefighting foams). They’re measured in ng/L (parts per trillion), which makes the numbers look “small” even when they’re meaningful.

Different states use different standards and advisories, and those benchmarks can change as research evolves. If PFAS is detected, your next steps usually include confirming which PFAS were tested, whether the panel included the key compounds, and whether the result is above a state guideline.

Treatment for PFAS often involves activated carbon or reverse osmosis, but the best approach depends on the specific PFAS profile and your household water usage.

VOCs: fuel-related and solvent-related compounds

VOCs include chemicals like бензene (benzene), toluene, and other fuel-related compounds, as well as dry-cleaning solvents and industrial degreasers. They can enter groundwater from spills, leaking tanks, or historical land use.

VOCs may cause taste/odor issues, but not always. If you see VOCs on your report, take them seriously and consider follow-up sampling to confirm the result and rule out sampling contamination (for example, fumes from a nearby garage can sometimes affect sample handling).

Because VOCs can volatilize (evaporate), treatment may involve specialized carbon systems and, in some cases, aeration technologies depending on the compound and concentration.

Physical water quality indicators: hardness, pH, alkalinity, and why they shape everything else

Some of the most important “numbers” on a water report aren’t contaminants at all—they’re indicators that determine how water behaves in your home. Hardness influences scale. pH and alkalinity influence corrosion and metal leaching. TDS (total dissolved solids) gives a broad sense of mineral content.

These parameters help explain why two neighbors can have the same contaminant level but different experiences. One home might have staining and clogged fixtures, while another doesn’t—because pH, oxygen, and hardness change how minerals dissolve and deposit.

Understanding these basics also helps you avoid mismatched treatment. For example, installing a softener without addressing low pH might not solve blue-green staining from copper corrosion.

Hardness: the scale-maker that sneaks up on appliances

Hardness is mainly calcium and magnesium. It’s usually reported in mg/L as CaCO3 (or sometimes grains per gallon). Hard water isn’t typically a health concern, but it’s a major comfort and maintenance issue: soap scum, dull hair, spotty dishes, and scale buildup in water heaters.

Scale reduces efficiency. A water heater working against scale uses more energy and may fail sooner. Coffee makers, dishwashers, and tankless heaters are especially sensitive.

If your hardness is moderate to high, a water softener is a common solution. But it’s best chosen in context—especially if you also have iron or manganese, because combined issues may require a specific setup.

pH and alkalinity: the corrosion controls

pH tells you how acidic or basic your water is. Low pH water can be corrosive, which means it can dissolve metals from plumbing and fixtures. That’s one reason lead and copper can show up even when the source water is “clean.”

Alkalinity is the water’s buffering capacity—its ability to resist pH changes. Low alkalinity can make pH unstable and can worsen corrosion issues. Some reports list “corrosivity index” or related calculations to help interpret risk.

If your pH is low, treatment often involves neutralization (adding minerals back in) rather than filtering something out. It’s a different mindset: you’re adjusting water chemistry to protect your home.

TDS and conductivity: broad indicators, not diagnoses

TDS is total dissolved solids—basically the sum of minerals and salts dissolved in water. Conductivity is related and often used as a quick proxy. Higher TDS can mean more minerals (which might be totally normal), or it can indicate salt intrusion, road salt impacts, or other sources depending on your area.

On its own, TDS doesn’t tell you what’s in the water. It’s more like a “zoomed out” view. If TDS is high, you might look closer at sodium, chloride, sulfate, and specific metals to understand why.

Homeowners often notice high TDS as a taste issue—water can taste “salty” or “mineral-y.” But again, the fix depends on what’s driving the number.

Radon in water: when your test result relates to air quality too

Radon is best known as an indoor air issue, but it can also be present in well water—especially in areas with certain bedrock. When you use water for showering, laundry, and dishes, radon can be released into the air. That means a water test result can connect directly to your home’s overall radon exposure.

Radon in water is measured in pCi/L. There isn’t a single universally applied federal MCL for private wells, so homeowners often rely on state guidance and risk-based recommendations. If your water radon is high, it’s also smart to test indoor air radon, because the combined picture is what matters.

Radon in water can’t be filtered the same way you’d filter sediment. It’s a gas, so the most effective methods typically involve removing it before it enters household plumbing or venting it safely.

What a radon-in-water number suggests about your next steps

If radon in water is detected at a meaningful level, homeowners often ask two questions: (1) Is my indoor air radon also elevated? and (2) Is the water contribution significant enough to warrant treatment at the point of entry?

In many cases, addressing indoor air radon is the first priority because it’s often the larger exposure pathway. But if water radon is high, treating the water can reduce the radon released during normal water use.

Because radon levels can vary, confirmatory testing and a plan that considers both air and water is usually the most sensible approach.

How water radon is typically treated in a home

The two common strategies are aeration (stripping radon out of water and venting it) and granular activated carbon (capturing radon, with considerations for media handling). Aeration is often preferred for higher levels because it removes radon rather than storing it in a filter tank.

If you’re researching equipment, you may come across options designed specifically for New Hampshire homes, such as a radon mitigation water aerator NH solution that focuses on effective removal and safe venting.

Whatever method you choose, make sure it’s sized to your flow rate and household demand. Undersized systems can struggle during peak use (like multiple showers), which is exactly when you want reliable performance.

Municipal vs. well water: why the same “contaminant” can mean different things

People sometimes assume municipal water is “always perfect” and well water is “always risky.” The reality is more nuanced. Municipal water is treated, disinfected, and monitored under regulatory schedules. Well water is untreated at the source but can be excellent quality—if it’s protected, tested, and treated appropriately when needed.

Your test results should be interpreted in context. For example, chlorine residual is normal for municipal water but unusual for a private well. Conversely, naturally occurring arsenic is a classic well-water issue but not common in treated municipal supplies (though it can still occur in source water before treatment).

Another difference: municipal water often includes disinfection byproducts (like THMs/HAA5) that aren’t typically present in well water unless the well is chlorinated continuously. So your “ideal” treatment goals can differ depending on where your water comes from.

What to look for if you’re on town water

If you’re on municipal water, your town’s Consumer Confidence Report (CCR) is a great baseline. But it reflects water quality in the distribution system overall, not necessarily what’s happening at your kitchen tap—especially if your home has older plumbing.

Many municipal-water homeowners test for lead/copper at the tap, plus basic parameters like hardness and chlorine. If taste and odor are your main complaints, chlorine and chloramine are common culprits, along with seasonal changes in treatment.

If you’re exploring filtration for a town supply, a targeted approach can be more effective than a one-size-fits-all system. For example, a municipal water filter Bedford NH style solution is typically designed around common municipal issues like chlorine taste, sediment, and overall water aesthetics—without overcomplicating the setup.

What to look for if you’re on a private well

Well owners usually benefit from a routine testing schedule: bacteria annually, nitrates periodically (often annually if risk factors exist), and a broader chemistry/metals panel every few years or when something changes (taste, staining, plumbing work, nearby construction).

If your report shows multiple concerns, don’t panic. It’s common to see a mix of “health” and “home comfort” issues. The smartest path is to tackle the health-based items first, then address corrosivity and nuisance items that affect your home’s infrastructure.

Also remember that wells are systems, not just holes in the ground. The well cap, casing, pressure tank, plumbing materials, and even your water heater all influence what you see at the tap.

Matching results to solutions: how homeowners prioritize without overspending

When you see a long list of results, it’s tempting to buy the biggest system you can find and hope it covers everything. But the best water treatment plans are usually built in layers: address the highest-risk contaminants with the most reliable method, then fine-tune for taste, staining, and scale.

Another helpful mindset: some problems are best solved at the point of entry (treating all water coming into the home), while others are best solved at the point of use (like a dedicated drinking water faucet). You don’t always need whole-house reverse osmosis to get great drinking water.

If you’re unsure where to start, getting a complete, well-designed test panel is often the most cost-effective first step. It prevents “trial-and-error” purchases that don’t match your chemistry.

Which issues are “whole-house” problems vs. “drinking water” problems

Whole-house priorities often include bacteria (if using continuous disinfection), hardness (to protect appliances), iron/manganese (to stop staining), and corrosivity (to protect plumbing). These affect showers, laundry, and fixtures—so treating at the point of entry makes sense.

Drinking-water priorities often include arsenic, lead, PFAS, and nitrate—contaminants where you care most about what you ingest. Many homeowners choose point-of-use systems for these, especially if the rest of the water is fine for bathing and cleaning.

Sometimes you need both. For example, if water is corrosive and also has lead at the tap, you may want corrosion control for the whole house and a drinking-water filter for an extra margin of safety.

Why “supporting parameters” help avoid the wrong treatment

Some treatment methods work beautifully in one chemistry and struggle in another. High iron can foul certain media. Low pH can reduce performance or damage components. Hardness can cause scaling in equipment that isn’t designed for it.

This is why good testing includes not just the “headline contaminant,” but also the supporting cast: pH, hardness, alkalinity, iron, manganese, sulfate, chloride, and sometimes silica or dissolved oxygen depending on the issue.

If you’ve ever heard someone say, “We installed a filter and it didn’t work,” there’s a good chance the underlying water chemistry wasn’t accounted for.

When to retest, and how to make retesting actually useful

Water testing isn’t always a one-and-done event. Retesting helps you confirm that a result is real (not a sampling anomaly), track seasonal patterns, and verify that treatment is doing what it should. The best retesting schedule depends on your water source, your risk factors, and whether you’ve installed any new treatment equipment.

Retesting is especially valuable after major events: flooding, well repairs, pump replacement, plumbing renovations, or a change in water taste/odor. Even a new baby in the home can be a reason to update your testing priorities.

The key is consistency. Use the same sampling location and similar conditions when possible (first-draw vs flushed, after the well sits overnight, etc.), so you can compare results meaningfully.

Sampling tips that can prevent confusing results

Follow the lab’s instructions exactly—especially for bacteria and VOCs. For bacteria, avoid touching the inside of caps, remove aerators if instructed, and don’t disinfect the faucet right before sampling unless the lab says to.

For metals like lead and copper, the timing matters. “First draw” usually means the water sat in the pipes for at least 6 hours. If you accidentally run water first, you’ll change the story the sample tells.

Label samples carefully and deliver them within the required time window. Some tests degrade quickly if they sit too long or get warm.

Verifying treatment performance (and catching maintenance issues early)

If you install treatment, plan a follow-up test to confirm it’s working—especially for health-based contaminants like arsenic, nitrate, PFAS, or radon. Don’t rely solely on “it tastes better” as proof.

Over time, filters saturate, media exhausts, and settings drift. A simple annual check can catch problems before they become expensive—like a softener that’s not regenerating properly or carbon that’s past its effective life.

Keeping a small “water folder” with your lab reports, equipment specs, and maintenance dates makes homeownership easier than you’d expect. It’s also a nice asset if you sell your home.

Choosing the right testing help in New Hampshire: what “comprehensive” should include

Not all water tests are created equal. Some are quick screens, others are full panels. Some are designed for real estate transactions, others for ongoing household health. If you’re trying to make confident decisions, “comprehensive” should mean the test covers both the likely contaminants in your area and the supporting parameters needed to pick the right treatment.

In New Hampshire, many homeowners prioritize bacteria, nitrates, arsenic, uranium (in some areas), lead/copper at the tap, iron/manganese, hardness, pH/alkalinity, and—depending on location—PFAS and radon in water. Your exact list should match your home’s risk factors and history.

If you want a starting point for building that kind of complete picture, exploring comprehensive water testing services NH can help you understand what a well-rounded testing and interpretation process looks like—especially when you’re trying to connect lab numbers to real, practical next steps.

Questions to ask before you pay for a test

Ask what the panel includes, what the reporting limits are (especially for PFAS and arsenic), and whether the lab is certified for the methods being used. Also ask whether the results will be explained in plain language with actionable recommendations.

If you’re testing because of a specific concern—like a neighbor’s nitrate issue, a local PFAS news story, or persistent staining—mention that upfront. A good testing plan is tailored, not generic.

Finally, ask how sampling should be done and whether you’ll need multiple sample bottles or different sampling locations. The best results come from good sampling, not just good lab equipment.

How to use your results to plan upgrades over time

Not every home needs to fix everything at once. If your results show a mix of issues, you can often phase improvements: handle health-based drinking water concerns first, then protect plumbing and appliances, then polish taste and odor.

This phased approach is especially helpful if you’re budgeting for a larger home upgrade (like a new water heater or bathroom remodel). Water chemistry affects those investments, so aligning upgrades with water improvements can save money long-term.

And if your results are mostly good? That’s also valuable. Knowing your water is in good shape lets you focus on simple maintenance and periodic retesting instead of guessing.

A quick cheat sheet for common report items (and what they usually mean at home)

Sometimes it helps to see the “translation” at a glance. Here are common items homeowners ask about, along with the most typical real-world meaning. (Always compare your numbers to the guideline used on your specific report.)

Total coliform positive: system vulnerability; inspect wellhead and consider resampling and/or disinfection steps.

E. coli positive: urgent; treat as a potential health risk, investigate source, correct, and retest.

Arsenic detected: common in bedrock wells; consider treatment for drinking water and confirm with follow-up testing if near guideline.

Lead at tap: often plumbing-related; consider corrosion control and point-of-use filtration.

Nitrate elevated: possible septic/agricultural influence; check well protection and consider treatment for drinking water.

Hardness high: scale risk; softening can protect appliances and improve cleaning comfort.

pH low: corrosive tendency; neutralization can protect plumbing and reduce metal leaching.

Iron/manganese high: staining and maintenance headaches; treatment depends on form and chemistry.

PFAS detected: consider guideline comparison and targeted treatment; confirm panel scope and reporting limits.

Radon in water high: consider both water treatment and indoor air radon testing for a complete risk picture.

Your water report is a tool, not a verdict. Once you understand what the numbers are telling you, the path forward becomes much clearer—and usually more affordable than “guess and replace.”