TDS measurement is one of the fastest ways to estimate how many dissolved minerals, salts, and other ions are in your water. The result shows up as ppm (mg/L), and it’s often the first number people check when water tastes “off,” leaves white scale on faucets, or when a filter seems to stop working. Most home meters don’t “count particles” directly. Instead, a TDS meter measures the conductivity of the water (called electrical conductivity, or EC) and converts it into a TDS estimate. That’s helpful—but it also has limits. This guide starts with clear answers (safe ranges, what readings mean, how to test), then moves into meter choice, calibration, accuracy, and real examples for reverse osmosis and pools.
What TDS Means (and What It Doesn’t)
Before diving into the details, it helps to clear up a common misunderstanding: TDS is informative, but it’s not the whole story. That single number can give you a general snapshot of what’s dissolved in your water, but it can’t tell you everything about quality, safety, or taste. Keeping that in mind will make the definitions and comparisons below much easier to understand.
Definition: Total Dissolved Solids (ppm / mg/L) in plain language
TDS stands for total dissolved solids, or in other words, the total amount of dissolved solids in your water that are small enough to pass through a simple filter screen. These can be inorganic substances (like calcium, magnesium, sodium, and salt) and some organic substances (like tiny amounts of natural organic matter). It can also include unwanted things, such as certain metals or residues from water treatment chemicals like chlorine.
TDS is usually reported as parts per million (ppm). For water, ppm is roughly the same as mg/L (milligrams per liter). So if your tds level is 300 ppm, it means there are about 300 milligrams of dissolved solids in one liter of water.
A key point is that what does TDS measure? It measures the amount of dissolved solids, not which ones. Two water samples can have the same TDS and be very different in safety and taste.
TDS vs “water purity”: beneficial minerals vs unwanted solids
People often treat TDS like a “purity score.” It’s tempting, because it’s a single number. But tds meter readings do not tell you if the dissolved solids are “good” or “bad.”
For example, minerals like calcium and magnesium are normal in many water sources. They can improve taste and help some people meet mineral intake goals. On the other hand, dissolved solids can also include things you might not want, like extra sodium, certain metals, or runoff-related ions. A TDS reading alone can’t separate these.
That’s why 0 ppm does not automatically mean “safer.” It usually means the water is highly demineralized (often from reverse osmosis or distillation). It may be very clean, but it can also taste flat because there are few minerals left to carry flavor.
TDS classifications by water type (fresh, brackish, saline)
This is a quick way to understand what category your tds in water falls into.
| Fresh | Brackish | Saline |
| < 1,000 ppm | 1,000–10,000 ppm | 10,000–35,000 ppm |
If your home has tap water in the 200–600 ppm range, that’s still “fresh” water by this classification, even if it causes scale.
Is low TDS water bad for you?
Low TDS water is not automatically bad. Many people drink low TDS ro water every day with no problems. The bigger question is what your overall diet looks like.
Still, very low TDS water can taste “empty,” and some people prefer a little mineral content to make water taste better — especially for tea and coffee. If you eat a normal diet with mineral-rich foods, water is rarely your main mineral source. But if your water is your main source of certain minerals, removing them may matter more.
If you have a medical reason to limit minerals (or to increase them), it’s smart to talk with a clinician and look at your full intake, not just the meter number.
TDS Measurement Standards, Ranges, and “What’s Safe”
To make sense of the numbers, it helps to know how TDS is viewed by water authorities. In most guidelines, TDS is not a strict safety limit but a reference for taste, appearance, and everyday usability. With that context, the standards and ranges below are easier to interpret and apply to real drinking-water decisions.
Drinking-water benchmarks (EPA/WHO/Canada) and what they imply
Many people search for “safe TDS.” The confusing part is that most major agencies treat TDS mainly as an aesthetic issue, not a direct health limit.
In the U.S., TDS has a common guideline of < 500 ppm as a secondary (non-enforceable) standard. That “secondary” label matters. It means the number is tied to taste, odor, and appearance more than proven health harm at slightly higher levels. Canada and global guidance often discuss similar acceptability ranges.
So what does that mean for you at the kitchen sink? If your tds in drinking water is 450 ppm, that does not automatically mean it’s unsafe. It suggests you might notice more taste, more scaling, or more buildup in appliances. If it’s 900 ppm, the risk of poor taste and scale rises, and you may want water testing beyond TDS to find out why it’s high.
Interpreting the most common ppm ranges (quick decision matrix)
People usually want a simple answer to: What is a good TDS level? The practical answer is “a range,” because taste and water source vary. Here’s a straightforward way to read the number.
| TDS range (ppm) | What you may notice | What to do next |
| < 50–250 | Very low minerals; can taste flat | Fine for most people; consider remineralization for taste/coffee if desired |
| 300–500 | Often pleasant taste; balanced minerals | Good baseline; monitor for seasonal shifts |
| 600–900 | Elevated; scale buildup more likely | Check hardness and alkalinity; consider filtration if taste/scale is a problem |
| > 1,000 | Often strong taste; can stress plumbing and appliances | Consider a full water report and a treatment plan |
A helpful habit is to compare your tds reading to how your water behaves. Does soap lather well? Do you see white spots on glasses? Does your kettle scale quickly? Those clues help you decide what to test next.
Non-drinking benchmarks (pools, hydroponics, aquariums, brewing)
TDS matters outside the kitchen too, but the “good” number changes by use.
| Application | Useful TDS benchmark | Why it matters |
| Pools | Keep TDS ≤ 1,500 ppm above fill water | High TDS can increase corrosion risk and complicate water balance |
| Hydroponics | Depends on crop and nutrients | TDS (or EC) helps track nutrient strength |
| Aquariums | Depends on species | Fish and plants can be sensitive to mineral changes |
| Brewing/coffee | Often needs moderate minerals | Minerals affect flavor extraction and scaling |
If you manage a pool, the key comparison is not just “your TDS.” It’s how far it is above your source water. A pool can gain TDS over time as chemicals dissolve, water evaporates, and solids stay behind.
What is a good TDS level for drinking water?
For many households, 300–500 ppm is a common “sweet spot” for taste. But “good” also means “fits your goal.” If you want less scale and you don’t care about mineral taste, a lower number from water filtration can be a win. If you want better coffee flavor, you might prefer moderate TDS instead of extremely low TDS.
How TDS Meters Work (EC → PPM Conversion)
TDS meters don’t measure solids directly—they infer TDS from how water behaves electrically. Understanding that indirect link explains why these meters are quick and useful, but also why their readings can differ from one device to another. The sections below break down the basic science behind the numbers you see on the screen.
Conductivity basics: why ions increase EC
A tds meter for water works because dissolved ions carry electrical charge. When water has more dissolved ions, it conducts electricity better. That’s conductivity (EC), often shown as µS/cm.
So the simple relationship is:
More dissolved ions → higher EC → higher estimated TDS
This is why TDS meters are so popular. They’re fast, cheap, and good at showing changes—like whether a filter is still removing dissolved minerals.
The conversion factor (kₑ) and why readings vary by meter
Here’s the part most people never hear until they compare two meters and get two different results.
Most meters use a conversion factor (often called kₑ) to estimate TDS from conductivity:
TDS (mg/L) ≈ kₑ × EC (µS/cm @ 25°C)
Common kₑ values range from 0.55 to 0.8. The “right” factor depends on what’s dissolved in your water. Water high in sodium chloride may convert differently than water high in calcium bicarbonate. That means two meters can show different tds meter readings even if both are working normally.
Here’s a quick mini chart to show how much the factor changes the result:
| EC (µS/cm) | k = 0.55 | k = 0.70 | k = 0.80 |
| 500 | 275 ppm | 350 ppm | 400 ppm |
| 1,000 | 550 ppm | 700 ppm | 800 ppm |
If your meter doesn’t tell you the factor it uses, treat the number as a trend tool, not a lab result.
Temperature compensation (ATC) and measurement conditions
Conductivity changes with temperature. Warm water conducts better than cold water, even if the dissolved solids are the same. Because of that, EC is often standardized to 25°C.
Many meters include ATC (automatic temperature compensation). ATC helps, but it does not make every reading perfect—especially if you test water that is very hot or very cold. A common mistake is testing water right after boiling or right after it comes from a very cold line. Let the sample sit for a few minutes and reach room temperature if you want more stable results.
Are TDS meters accurate?
They are accurate enough for what they are designed to do: estimate dissolved ion content based on conductivity. For home use, a good meter can be quite repeatable, meaning it gives the same number when you test the same sample the same way.
But they are not “contaminant detectors.” They don’t tell you if you have lead, pesticide residue, a pharmaceutical, or microbes. Also, they can be off if the conversion factor doesn’t match your water chemistry, if the probe is dirty, or if calibration is neglected.
TDS Measurement: Step-by-Step Testing Protocol (Home to Field)
This section answers the questions people ask most: How do you measure TDS? and how to use tds tester without getting random numbers.
Pre-test checklist: sample cup, rinse steps, avoid contamination
A clean sample makes a big difference. You don’t need lab gear, but you do need consistency.
Use a clean cup (glass or food-safe plastic). If it has soap residue, your tds meter test can drift upward. Rinse the cup with the same water you’re about to test, then discard that rinse water. Do the same for the meter probe: rinse it with the sample water before taking the real reading.
Try not to touch the electrodes with your fingers. Skin oils and residue can affect readings over time. Also, avoid foam and bubbles around the probe tip, because bubbles can make readings jump.
How to take a stable reading (repeatability + logging)
If you want numbers you can trust, you need a simple routine.
How to use a TDS meter step by step
| Step | What to do | Why it matters |
| 1 | Fill a cup with a fresh water sample | Stagnant water can read differently |
| 2 | Rinse the probe with the same sample | Reduces cross-contamination |
| 3 | Place the probe tip into the water (don’t hit the sides) | Prevents false readings |
| 4 | Gently stir once, then hold still | Helps the sensor stabilize |
| 5 | Wait for the number to stop changing | This is your stable tds reading |
| 6 | Write it down with date/time/source | Trends matter more than one reading |
This is also how to read TDS meter reading in a practical way: don’t chase the first number that flashes. Wait for stability, then record it.
A simple logging habit can save you money. For example, if your kitchen water filter usually drops TDS from 400 to 150, and you notice it now only drops to 320, you have a clear sign the filter performance changed.
Here’s a simple log template you can copy into notes or a spreadsheet:
| Date | Location | Source (tap/fridge/RO) | Temp (rough) | TDS (ppm) | Notes |
Quick troubleshooting: high/erratic readings and fixes
Sometimes a meter seems “wrong,” but it’s really the test setup. Use this quick decision path to diagnose common problems.
Decision-tree (symptom → cause → fix)
| Symptom | Likely cause | Fix |
| Reading jumps up and down | Air bubbles or moving probe | Tap probe gently, keep still, stir once then stop |
| Reading is higher than usual everywhere | Dirty probe or mineral crust | Clean probe, remove scale buildup, retest |
| Reading slowly creeps upward | Cup has residue or sample is warming | Use a clean cup, let sample reach room temp |
| Reading seems “stuck” | Low battery or sensor issue | Replace battery, check calibration |
| Tap reads normal but filtered reads higher | Filter media release or wrong sample order | Run water longer, rinse cup, test again |
How do you measure TDS in water at home?
Use a clean cup, rinse the probe, test at a steady temperature, wait for the reading to stabilize, and log the result. The goal is consistency. If you repeat the same method, you can spot real changes in your home water over time.
Choosing the Right TDS Meter (and Alternatives)
Picking a TDS meter isn’t about finding the “best” device overall—it’s about matching the tool to how precise you need to be and how often you’ll actually use it. Once you’re clear on your use case, the differences between meter types and alternatives become much easier to evaluate.
Handheld TDS pens vs benchtop meters vs pro multiparameter kits
If you only need quick checks, a handheld pen-style tester is often enough. It’s the classic portable TDS meter you can keep in a drawer. If you run a small lab, manage water systems, or need documented results, a benchtop unit may fit better. Some people also prefer multiparameter tools that measure EC, temperature, and sometimes other values.
Here’s a direct comparison to help you choose a digital water tester that matches your use case:
| Type | Best for | Typical range | Typical resolution | ATC | Calibration | Price band |
| Pen-style handheld | Quick home checks, travel | 0–999 / 0–9,990 ppm | 1–10 ppm | Often | Sometimes | Low |
| Portable “pro” meter | Field work, pools, hydroponics | Wider ranges | Better stability | Often | Yes | Medium |
| Benchtop meter | Lab or detailed records | Very wide | High precision | Yes | Yes (multi-point) | High |
What specs matter most: range, resolution, ATC, electrode quality
When people buy a tds meter, they often focus on price first. It’s usually better to start with your goal.
If your water supply is usually under 600 ppm, a 0–999 ppm meter can work. If you expect higher values (some wells, brackish water, pool water over time), choose a wider range so you don’t max out the display.
Resolution is the smallest step the meter shows. A 1 ppm resolution feels nice, but it doesn’t guarantee accuracy. Electrode quality and calibration matter more for reliable tds meter readings.
ATC is worth having because household water temperature changes through the year. Without it, your morning winter reading may look “better” than your summer reading even if the dissolved solids didn’t change much.
Alternatives: test strips, lab tests, and when to use each
Test strips are simple and cheap, but they are usually less precise. They can be useful for a quick check, but don’t expect them to track subtle filter changes.
Lab tests are the opposite: slower and more expensive, but they tell you what’s actually in the water. If your TDS is high and you want to know why, a lab panel can identify specific ions and possible contaminant concerns. That matters because TDS can’t tell you whether the dissolved solids are mostly harmless minerals or something you need to address.
“Buyer intent” mini-guide: what to avoid in cheap meters
A very cheap meter can still be useful, but certain red flags lead to frustration. If the meter has no clear way to calibrate, if readings are unstable in the same sample, or if it never states its conversion factor or range, treat it as a rough indicator only.
Accuracy, Calibration, and Maintenance (Make Readings Trustworthy)
Getting consistent and trustworthy TDS readings isn’t just about pressing a button. How often you calibrate your meter, how your water chemistry interacts with the electrodes, and basic maintenance all play a role. This section breaks down why readings can drift, what affects accuracy, and simple steps to keep your meter giving reliable numbers every time.
Calibration frequency and solutions (typical standards)
Calibration is how you keep your meter honest. Over time, probes drift. That’s normal. A calibration routine helps you trust your trendline.
For light home use, calibrating monthly is a reasonable starting point. For heavy use (pools, hydroponics, frequent testing), calibrate more often. Always use a certified calibration solution and keep the cap closed so the solution doesn’t change from evaporation.
If you skip calibration, you may still get a number—but you won’t know if it’s the real tds level or just drift.
How water chemistry skews readings (hardness, salinity, organics)
Because TDS meters estimate based on conductivity, different mixes of ions can skew the conversion.
Hard water is often high in calcium and magnesium, which drive scale. Salty water is high in sodium and chloride, which drives salinity and can raise corrosion risk in some settings. Both can raise TDS, but they behave differently in water systems and taste.
Also, some dissolved substances do not conduct well, so they don’t show up strongly in EC. That’s another reason TDS is a useful indicator, but not a full answer to “ what’s in your water. ”
Maintenance: cleaning electrodes + storage best practices
If your meter starts acting strange, cleaning is often the fix.
Rinse the probe after every use. If you see visible mineral buildup, soak the probe tip in a cleaning solution recommended for electrodes, then rinse and retest. Avoid scraping the sensor with something sharp, which can damage it.
Store the meter capped to keep the electrodes clean and protected. And don’t forget the simplest fix of all: a fresh battery. Low battery can cause erratic reading behavior.
Meter anatomy (quick mental model)
Even basic meters share the same parts: a display, buttons, a probe tip with electrodes, and often a temperature sensor for ATC. When you treat the probe like a sensitive measurement surface—not a stir stick—your results get more stable.
EC-to-TDS calculator (with selectable k-factor)
You can estimate TDS from conductivity if you know the conversion factor your meter uses.
Formula: TDS (ppm) ≈ k × EC (µS/cm at 25°C)
Example: if your measured EC is 900 µS/cm and your meter uses k = 0.7: TDS ≈ 0.7 × 900 = 630 ppm
If you repeat the same calculation with k = 0.55, you get 495 ppm. With k = 0.8, you get 720 ppm. That spread is why two meters can disagree while both are “reasonable.”
Real-World Case Studies: RO, Pools, and the “0 ppm” Myth
Seeing TDS numbers in action makes the concept clearer. Whether you’re checking a reverse osmosis system, managing pool water, or thinking “0 ppm is best,” real-world examples show why context matters. This section walks through practical cases and highlights what TDS can—and can’t—tell you about your water.
RO performance check using TDS (rejection rate calculation)
One of the best real uses of tds measurement is checking a reverse osmosis system.
You measure the feed water (often your tap) and the RO output. Then you calculate rejection rate:
Rejection (%) = (Feed TDS − Product TDS) / Feed TDS × 100
Example: feed is 260 ppm and RO water is 20 ppm.
Rejection = (260 − 20) / 260 × 100 = 92%
That’s a strong result for many home systems. If your rejection drops over time, it may point to membrane aging, poor prefiltration, or pressure issues. In this case, the meter is doing its job well: showing performance change, even though it can’t identify which ions remain.
Pools: high TDS impact on balance, corrosion, scaling
Pool water is a great example of how TDS is about systems, not just drinking.
As pool chemicals dissolve and water evaporates, water’s TDS rises. Higher TDS can shift water balance and can increase the chance of corrosion in some conditions. Pool operators often use a practical rule: keep TDS no more than 1,500 ppm above the fill water. If your fill water is 400 ppm, you start getting concerned as the pool approaches about 1,900 ppm.
This does not mean “drain the pool the moment you hit the number.” It means you should look at the full balance picture and plan water replacement if problems appear.
0 ppm controversy: why “lowest TDS” isn’t the whole story
It’s easy to think the best water is always the lowest number. But here’s the catch: TDS can drop because you removed helpful minerals, not only harmful ones.
Also, TDS cannot confirm the absence of specific contaminants. You could have low TDS and still have an issue that doesn’t show up strongly on a conductivity-based test, or an issue that needs a specific measurement (like microbes).
A smart takeaway is this: use TDS to track your water filtration system, but pair it with targeted tests when safety is the goal.
If you have an older home or older plumbing, consider testing for metals like lead even if your TDS is low. If your source is a private well, consider nitrate testing. If you suspect illness risk, remember microbes require different tests than a TDS pen can offer.
Does boiling water reduce TDS?
Boiling usually does not reduce TDS. In many cases it can increase the reading, because some water evaporates while dissolved solids stay behind, so the remaining volume of water is smaller and more concentrated. Boiling can kill many microbes, but it doesn’t remove dissolved minerals and salts.
TDS vs Related Water Quality Metrics (Know What to Test Next)
TDS gives a quick snapshot, but it’s just one piece of the puzzle. Comparing it with related metrics like EC, hardness, alkalinity, pH, or specific contaminants helps you understand what’s really happening in your water and decide what to test next.
TDS vs EC: when to use which number
EC is the direct measurement. TDS is the estimated, converted number.
| Metric | What it is | What it’s best for | Main limitation |
| EC (µS/cm) | Direct measure of conductivity | Comparing ion strength across samples | Less intuitive for most people |
| TDS (ppm) | EC converted using a factor | Quick “how mineralized is it?” checks | Depends on conversion factor; doesn’t identify substances |
If you work in hydroponics, you may prefer EC because it maps more directly to nutrient strength. If you’re doing basic home checks, TDS is easier to interpret.
TDS vs hardness (Ca/Mg) vs alkalinity vs pH
This question comes up all the time: Does high TDS mean hard water? Not always.
Hardness is mainly about calcium and magnesium. TDS includes everything dissolved, including sodium, chlorides, sulfates, and more. So you can have:
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High TDS and not-so-hard water (for example, if sodium salts are high)
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Hard water with moderate TDS (if calcium/magnesium are present but overall dissolved solids are not extreme)
Hardness links strongly to scale and soap behavior. Alkalinity relates to buffering (how water resists pH change) and can affect corrosion and scaling. pH is how acidic or basic the water is. These three—hardness, alkalinity, pH—often explain real-world problems better than TDS alone.
A practical set for homeowners is TDS + hardness + pH. If you’re managing a pool or boiler system, alkalinity becomes even more important.
TDS vs contaminants and microbes: what TDS can’t detect
TDS is not a safety guarantee. It cannot confirm the absence of:
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Pathogens (bacteria, viruses, parasites)
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Many chemicals at low levels
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Some metals at levels that matter for health
If you’re worried about microbes, rely on proper disinfection, source protection, and guidance from public health agencies. If you’re worried about metals, use a targeted metals test. If you’re worried about agricultural runoff, test nitrates.
Next-step testing map (by scenario)
Use your TDS as a clue, then choose the next test based on what you see and taste.
| Scenario | What it might mean | Next best test |
| High TDS + metallic taste | Possible metals or pipe issues | Metals panel (lead/copper), corrosion indicators |
| High TDS + scale buildup | Often hardness-related | Hardness + alkalinity |
| Low TDS + “flat” taste | Very low minerals | Mineral profile (optional), taste-based adjustment |
| Sudden change in TDS | Source change or treatment change | Retest, then check local water report or well conditions |
Action Plan: What to Do With Your TDS Reading
A TDS reading is a starting point, not the full story. How you respond depends on whether your water is low, moderate, or high in dissolved solids. This section shows practical steps for interpreting your numbers and deciding on taste adjustments, filter maintenance, or treatment options.
If TDS is low (≤250 ppm): taste, minerals, and use-case decisions
If your low tds level is under about 250 ppm, you’re in the “very low to low mineral” zone. Many people like it, especially if they dislike mineral taste. Others feel it tastes flat.
If taste is your only concern, you can leave it alone. If you want better flavor for tea or coffee, remineralization can help. Some people also notice that very low TDS water feels different on the tongue, which is normal.
If your goal is health, focus on your total diet. Water is only one piece of mineral intake.
If TDS is moderate (300–500 ppm): maintenance and monitoring
This range is often comfortable for taste and normal for many local water sources. If you’re here and your water tastes fine, you may not need major changes.
The smart move is to create a baseline. Measure once a week for a month, then once a month. Many water supplier systems shift seasonally as they blend sources. If you track that pattern, you’ll be less surprised when your kettle scales faster in summer or when your tds meter readings change after a storm.
This is also where a TDS meter can help you time filter maintenance. If your filtered water slowly climbs back toward your tap’s TDS, it’s a sign the filter is no longer reducing dissolved solids as well as before.
If TDS is high (≥600 ppm): treatment options with pros/cons
If you’re seeing high tds (especially 600–900+ ppm), the next step is to ask: what problem are you solving?
If the problem is taste and scale, you usually want to reduce dissolved minerals. If the problem is a specific contaminant, you need targeted treatment based on a real test result.
Here are common options and what they are best at:
| Treatment | Best at removing | What to know | Typical TDS reduction |
| Reverse osmosis | Many dissolved ions | Needs pressure and maintenance; produces some waste water | 90–99% |
| Distillation | Dissolved solids and many impurities | Slow; uses energy; may need post-treatment for taste | Very high |
| Ion exchange (softener) | Mainly hardness (Ca/Mg) | Replaces hardness with sodium/potassium; TDS may not drop much | Often modest |
| Blending | Reducing high TDS by mixing | Requires a lower-TDS source | Depends |
A common surprise: a water softener can make water feel better (less scale from calcium and magnesium) while not lowering TDS much, because it swaps ions rather than removing them. So if your main goal is lower amount of dissolved solids, a softener alone may not deliver the number drop you expect.
If your high tds level is coming from salty conditions or brackish well water, reverse osmosis or distillation is often the more direct approach.
Final checklist + key takeaway synthesis
You don’t need to turn water testing into a hobby to get value from it. Keep it simple:
Measure correctly so your reading is stable. Interpret it using realistic benchmarks, not fear. Confirm concerns with targeted tests. Then choose treatment based on your goal—taste, scale control, appliance protection, or safety.
If you take only one idea from this guide, let it be this: TDS is a fast signal, not a full diagnosis. It tells you how much is dissolved in water, not what it is. Use it to spot changes, compare sources, and check filtration. For everything else, test with the right tool.
FAQs
1. What does TDS actually measure?
TDS stands for Total Dissolved Solids, and it’s basically a way to estimate how much stuff is dissolved in your water. A TDS meter doesn’t test each substance one by one. Instead, it measures electrical conductivity, then converts that into a TDS value. So when you see a TDS number, you’re looking at the overall level of dissolved minerals and salts—things like calcium, magnesium, sodium, chlorides, and more. What it doesn’t tell you is what exactly those substances are or whether they’re good or bad. Think of TDS as a summary number, not a detailed ingredient list.
2. How to read a TDS meter reading?
Using a TDS meter is pretty straightforward. Turn it on, place the probe in the water, and give it a few seconds. The key is to wait until the number stops jumping around. Once it stabilizes, that’s your reading, usually shown in ppm (parts per million). For better accuracy—especially if you’re comparing water sources—it’s smart to take two or three readings and see if they’re consistent. If the numbers are close, you can be more confident in the result.
3. Does high TDS mean hard water?
Not necessarily. This is a really common misunderstanding. Hard water is mainly about calcium and magnesium. High TDS, on the other hand, just means there are a lot of dissolved solids overall. Those solids could be hardness minerals, but they could also be sodium, sulfates, chlorides, or other ions. So you can have water with high TDS that isn’t technically hard, and you can also have hard water with only moderate TDS. The two are related, but they’re not the same thing.
4. What is a good TDS level for drinking water?
There’s no single “perfect” number, but many people find that water in the 300–500 ppm range tastes pleasant—clean, but not flat. From a general guideline perspective, below 500 ppm is often used as an aesthetic benchmark, meaning taste and appearance are usually acceptable. That said, “good” really depends on your personal taste and your goals. Some people prefer very low TDS water (like RO water), while others like a bit of mineral content for flavor.
5. Does boiling water lower TDS?
No—boiling actually does the opposite. When you boil water, some of the water evaporates, but the dissolved solids stay behind. That means the remaining water can end up with higher TDS, not lower. So while boiling can help with microbes, it’s not a method for reducing TDS. If anything, it can slightly concentrate whatever minerals and salts were already there.
References