Cloudy pool water has a special talent for showing up at the worst possible time: the day you planned to host friends, the first hot weekend of the season, or right after you finally got the water looking great. One minute the pool looks like a sparkling postcard, and the next it’s more like a glass of skim milk. The good news is that cloudiness is almost always fixable—and usually without draining the pool or throwing a random pile of chemicals at it.

What makes pool water turn cloudy is pretty straightforward: tiny particles are suspended in the water, and your filtration/sanitation system isn’t removing or breaking them down fast enough. Those particles can be dead algae, living algae, pollen, dust, sunscreen oils, calcium scale, or even “invisible” chemistry issues that cause dissolved stuff to clump together.

This guide walks through the real causes of cloudy water, how to diagnose which one you’re dealing with, and the fixes that actually work. Along the way, we’ll also cover prevention habits that keep the water clear week after week—because nobody wants to play “pool detective” every Saturday.

Cloudy water isn’t one problem—it’s a handful of common ones

It’s tempting to treat cloudiness like a single issue with a single cure: add clarifier, shock the pool, and hope for the best. Sometimes that works by luck. But cloudiness can come from sanitation problems, filtration problems, circulation problems, chemistry balance problems, or a combination of all four.

The best approach is to identify what kind of cloudiness you have, then apply the matching fix. Think of it like a check-engine light: you can’t solve it by topping up windshield washer fluid. You need to read what the system is telling you.

Here’s the key idea: if you fix the cause, the cloudiness clears quickly. If you only treat the symptom, the cloudiness comes back (or never goes away).

Fast diagnosis: what does the cloudiness look like?

Milky white or gray haze

Milky or gray water often points to filtration issues, high calcium, pH/alkalinity imbalance, or a pile-up of fine particles that the filter isn’t catching. It can also happen after a heavy shock if the filter can’t keep up with the debris load.

If the water is “uniformly” cloudy (the same everywhere) and you don’t see green tones, start by checking your filter condition and your water balance—especially pH, total alkalinity, and calcium hardness.

This type of cloudiness is also common right after a big pool party: sunscreen, sweat, and dirt add a ton of tiny stuff that needs filtration time and enough sanitizer to oxidize it.

Cloudy with a green tint

If there’s any green cast, assume algae is involved—even if the pool isn’t fully green yet. Early algae blooms can look like “dull” water with reduced sparkle, then shift toward cloudy green.

Algae is a sanitation and circulation story. It thrives when free chlorine is too low for the stabilizer level (CYA), when the pump runtime is too short, when there are dead zones (steps, corners), or when the filter is dirty.

The fix here isn’t just “shock once.” It’s getting chlorine to the right level and holding it there long enough to finish the job while brushing and filtering continuously.

Cloudy after rain or wind

Storms dump pollen, dust, and organic debris into the water. Rain can also dilute the pool and mess with chemistry—especially if you were already on the edge with low sanitizer or high pH.

After weather events, cloudiness is usually a combination of fine particles plus a temporary sanitizer deficit. This is one of the easiest scenarios to fix if you respond quickly: skim, brush, clean the filter, and restore proper chlorine levels.

If you live in an area with frequent wind, consider that your pool is basically an outdoor bowl collecting airborne stuff. A little extra filtration time after windy days can prevent the haze from building up.

Cloudy right after adding chemicals

If you add calcium increaser, pH increaser, or alkalinity increaser and the water clouds up immediately, that’s usually a sign of localized precipitation—tiny particles forming because the water chemistry temporarily spiked in one spot.

This is especially common when chemicals are poured in too fast, added without pre-dissolving (where appropriate), or added with poor circulation. The fix is often improved circulation and filtration, plus rebalancing the water so those particles dissolve or get filtered out.

It’s also a reminder that “more” isn’t better. Pool chemistry is about hitting ranges, not chasing extremes.

The chemistry checks that matter most (and why)

Cloudy water is one of those problems where test results actually matter. Guessing leads to overcorrecting, and overcorrecting leads to more cloudiness. If you’re using test strips, consider confirming with a drop-based kit for better accuracy—especially for chlorine and CYA.

Below are the chemistry factors most tied to cloudiness, what they do, and what to aim for in a typical residential pool.

Free chlorine vs. stabilizer (CYA): the most common mismatch

Many pools look cloudy because free chlorine is “technically present,” but it’s not high enough for the amount of stabilizer (cyanuric acid) in the water. CYA protects chlorine from sunlight, but it also reduces how active chlorine is. That means the same 2 ppm free chlorine can be perfectly fine in one pool and totally inadequate in another.

As a rough guideline, many pool care approaches recommend keeping free chlorine at a percentage of CYA (often around 7.5% as a minimum for everyday sanitation). If CYA is 80 ppm and free chlorine is 2 ppm, algae and cloudiness can creep in even though your “chlorine isn’t zero.”

If your pool keeps getting dull or cloudy despite “normal” chlorine readings, test CYA and adjust your targets accordingly. Sometimes the real fix is lowering CYA (through partial water replacement) so chlorine can do its job again.

pH and total alkalinity: clarity killers when they drift

High pH reduces chlorine effectiveness and can encourage calcium scale formation—both of which can make water look hazy. Total alkalinity acts like a buffer that helps pH stay stable, but if alkalinity is too high, pH tends to rise constantly, and you end up in a cycle of chasing it.

Typical targets: pH around 7.4–7.6, total alkalinity often 70–90 ppm for many pools (some systems differ). If your pH is 7.9+ and the pool is cloudy, bring pH down first. You’ll often see clarity improve within a day once chlorine becomes more effective.

One tip: adjust in steps. Big swings can cause precipitation or make the water temporarily worse before it gets better.

Calcium hardness: when “too much of a good thing” turns into haze

Calcium hardness is important, especially for plaster pools, but high calcium combined with high pH can cause calcium carbonate to precipitate—tiny white particles that make the pool look milky. This is common in areas with hard fill water or when calcium increaser is added without checking current levels.

If your calcium is high and your water is cloudy white, focus on keeping pH in range and avoid adding more calcium. In some cases, partial drain/refill is the practical solution, but you can often manage it by lowering pH and keeping the water balanced so calcium stays dissolved.

Water balance is a “whole picture” issue. The same calcium level can behave differently depending on pH, alkalinity, and temperature.

Phosphates and nitrates: not the villain, but they feed the villain

Phosphates don’t directly cause cloudiness. What they do is feed algae. If your sanitizer is strong and well-matched to CYA, phosphates are usually a non-issue. But if chlorine routinely dips low, high phosphates can make algae bloom faster—and that leads to cloudy water.

If you’re battling recurring algae/cloudiness even with decent maintenance, phosphate testing can be useful. Removing phosphates can slow algae’s ability to rebound, but it’s not a substitute for proper chlorine levels and filtration.

In other words: treat phosphates as a “supporting fix,” not the main event.

Filtration and circulation: the hidden half of water clarity

Pool water can be perfectly balanced and still look cloudy if the filter isn’t capturing debris or the water isn’t moving enough to bring particles to the filter. Clarity is as much mechanical as it is chemical.

If your chemistry tests fine but the water stays hazy, it’s time to look at the system: filter condition, pump runtime, return eyeballs, and whether you’re actually pulling water from the whole pool (including the bottom).

Dirty or undersized filters

A filter that’s overdue for cleaning can’t trap fine particles effectively. In some cases, a very dirty filter can even channel water through gaps, reducing filtration. If the pressure gauge is 20–25% above your clean baseline, it’s usually time to clean/backwash.

Undersized filters are another common issue. If the filter is too small for the pool volume and bather load, it may never catch up, especially after storms or heavy use. You’ll see a repeating pattern: the pool looks okay, then turns cloudy, then clears slowly, then repeats.

Different filter types behave differently. Sand filters are great but may struggle with ultra-fine particles unless you use a small amount of filter aid (like DE) if your system allows. Cartridge filters can catch finer debris but need thorough cleaning. DE filters catch the finest particles but require more careful maintenance.

Not running the pump long enough (especially during trouble)

When the pool is cloudy, you want maximum turnover and filtration time. Running the pump “a few hours” might be fine for a perfectly stable pool, but it’s often not enough when you’re trying to clear suspended particles or kill algae.

During a cloudiness event, many pools benefit from running the pump continuously for 24–48 hours while you address chemistry and brush. Once clarity returns, you can reduce runtime to a normal schedule based on your pool size, pump type, and season.

If you have a variable-speed pump, longer runtime at a lower speed can be more efficient and may improve filtration because slower flow can help some filters capture finer particles.

Dead spots: the corners and steps that never get love

Cloudiness can persist because algae and debris sit in low-circulation zones: behind ladders, under steps, in corners, along the deep end floor, or in attached spas. If you’re only relying on returns and a robot, you may still have pockets of stagnant water.

Brushing is underrated. Brushing breaks up biofilm and algae so chlorine can reach it, and it lifts fine debris into suspension so the filter can capture it. During cloudy episodes, brush daily—especially steps, walls, and around fittings.

Also check your return eyeballs. Pointing them slightly downward and in a circular pattern can improve overall circulation and help push debris toward the main drain or skimmer.

The most common real-world causes of cloudy pool water

Let’s get practical. These are the scenarios that show up again and again for homeowners and property managers, and they’re usually the reason the water looks dull or hazy.

Cause: You shocked, but you didn’t finish the job

One-time shocking can kill a portion of contaminants, but if algae is present or the pool is loaded with organics, chlorine gets consumed quickly. The water may look a bit better, then stall at “cloudy blue,” or even slide back toward green.

The fix is maintaining an effective chlorine level long enough to fully oxidize contaminants and kill algae. That often means testing and re-dosing over a day or two, not just a single dump of shock.

Also: shock type matters. Cal-hypo adds calcium; dichlor adds CYA; liquid chlorine adds neither. Choosing the wrong one repeatedly can create a new problem while trying to solve the old one.

Cause: The filter is working… but it’s overwhelmed

After algae dies, it turns into tiny particles that cloud the water. At that stage, the pool may be sanitized, but it’s not clear yet. This is where patience and filtration win.

Clean the filter, run the pump longer, brush, and vacuum. If you vacuum to “waste” (where possible), you can remove a lot of dead algae and fine debris without sending it through the filter again.

If you’re using a robot, empty its basket frequently. A full basket reduces suction and leaves debris behind, which keeps the haze going.

Cause: High pH plus high calcium (or high alkalinity) causing precipitation

This is the classic “milky water” situation. You might notice a rough feel on surfaces, scaling on the waterline, or cloudy plumes when chemicals are added. The water can look like it has a white fog in it.

Lower pH gradually to the target range and avoid adding calcium-based products. If alkalinity is also high, lowering alkalinity (carefully) can reduce the constant upward drift of pH.

In stubborn cases, a professional water test and a plan for managing saturation (sometimes using the LSI/CSI balance approach) can save you weeks of frustration.

Cause: Too much stabilizer (CYA), not enough effective chlorine

High CYA is sneaky because the pool can still “hold chlorine” on a test, but it’s not active enough to prevent algae. The result is persistent dullness, recurring cloudiness, and frequent “mystery” blooms.

If your CYA is very high, the realistic fix is partial drain/refill to bring it down. After that, keep chlorine matched to CYA and avoid stabilized chlorine products as your everyday sanitizer unless you’re intentionally managing CYA.

This single issue is one of the biggest reasons people feel like they’re constantly fighting their pool.

Cause: Organic load from swimmers (and the stuff they bring in)

Lotions, sunscreen, makeup, sweat, hair products, and detergents from swimsuits all end up in the water. These can create combined chlorine (chloramines), reduce sanitizer effectiveness, and contribute to cloudy water—especially in smaller pools or during heat waves when the pool gets heavy use.

If cloudiness shows up after a busy weekend, boost filtration time, clean the filter, and consider an oxidizing shock (or a properly managed chlorine bump) to burn off organics. Encourage quick rinses before swimming if you can—small habit, big payoff.

Enzyme products can help break down oils, but they’re not magic. Think of them as a helper, not a replacement for sanitizer and filtration.

Fixes that actually work (in the right order)

Here’s the part most people want: the step-by-step plan. The key is doing things in an order that makes each step more effective. If you skip around, you can waste money and time.

Step 1: Get accurate test results first

Before you add anything, test: free chlorine (FC), combined chlorine (CC), pH, total alkalinity (TA), cyanuric acid (CYA), and calcium hardness (CH). If you have a salt pool, test salt level too. If you suspect metals, test for iron/copper.

Write the numbers down. It’s hard to troubleshoot when you’re relying on memory or “it looked okay.” Cloudiness is often a pattern, and your notes help you see it.

If your testing method is questionable, take a water sample to a reputable pool store for confirmation—but still keep your own baseline testing at home for day-to-day adjustments.

Step 2: Fix pH first (because it affects everything else)

If pH is high, bring it down to around 7.4–7.6. This increases chlorine effectiveness and helps keep calcium dissolved. If pH is very low, bring it up carefully—low pH can damage surfaces and equipment, and it can also make water look “off.”

Make adjustments in stages, allowing circulation time between doses. Add chemicals with the pump running and brush the area to avoid localized concentration.

If your TA is extremely high, you may need a longer-term plan to bring it down so pH doesn’t keep climbing and dragging clarity down with it.

Step 3: Raise and maintain chlorine to the right level for your CYA

If algae is suspected (green tint, slippery walls, recurring cloudiness), treat it aggressively and consistently. That means bringing FC up to a level appropriate for your CYA and keeping it there through repeated testing and dosing until the pool is truly done consuming chlorine.

Don’t forget to brush—chlorine can’t kill what it can’t reach. Brushing breaks up algae’s protective layer and exposes it to sanitizer.

If CC is elevated or the pool smells “chlorine-y,” that’s often a sign of chloramines and organics. Proper chlorination and oxidation clears that up.

Step 4: Let the filter do its job (and help it)

Once contaminants are dead, clarity becomes a filtration game. Run the pump longer, clean/backwash as needed, and vacuum debris. If your pool has a multiport valve, vacuuming to waste can remove a lot of fine material quickly.

For sand filters struggling with fine particles, a small amount of filter aid (if compatible with your setup) can improve clarity. For cartridge filters, a deep clean (not just a quick rinse) can make a huge difference.

Also check for simple mechanical issues: clogged skimmer baskets, a full pump basket, air leaks, or a stuck weir door. Any of these can reduce flow and slow clearing.

Step 5: Use clarifier or flocculant only when it matches the problem

Clarifiers work by binding tiny particles into larger clumps that the filter can catch. They’re useful when the pool is sanitized but still hazy due to fine debris. They’re not a cure for active algae or wildly imbalanced chemistry.

Flocculants (“floc”) drop particles to the bottom so you can vacuum to waste. Floc can be effective, but it’s easy to misuse and can gum up filters if you vacuum to the filter instead of waste. Use it when you can follow the directions precisely and you have the ability to vacuum to waste.

If you’re not sure, skip the additives and focus on chlorine, pH, brushing, and filtration first. Most pools clear without special products once the fundamentals are right.

When cloudy water is a sign of a bigger equipment issue

Sometimes, cloudy water keeps coming back because the system can’t support clear water reliably. This is where a lot of homeowners end up calling in help—not because they can’t do basic maintenance, but because something in the setup is working against them.

If you’ve balanced chemistry, cleaned the filter, increased runtime, and the haze still doesn’t improve after a couple of days, it’s worth looking deeper.

Filter media problems (sand channeling, old cartridges, DE grids)

Sand can channel when it clumps or when backwashing isn’t done properly, allowing water to bypass filtration. Cartridges can wear out or become permanently clogged with oils and scale. DE grids can tear or lose integrity, letting DE and debris return to the pool.

Signs include: debris returning through returns, filter pressure behaving oddly, or water that never quite gets “sparkly” even when chemistry is perfect. A filter inspection and proper service can be a game-changer.

If you suspect your filter simply isn’t capturing fine particles, it’s not always a chemistry problem—it can be a hardware problem.

Circulation design and hydraulic limitations

Return placement, skimmer performance, and pump sizing all influence how well the pool “collects” debris. If your pool has persistent dead zones, you may need to adjust return eyeballs, add a directional fitting, or change how long and when the pump runs.

Variable-speed pumps are great, but programming matters. Running too low for too long can reduce skimming action; running too high can reduce filtration efficiency in some cases. The sweet spot depends on your pool.

If you’re troubleshooting endlessly, talking to experienced pool contractors can help you see whether the issue is maintenance-related or system-related—because the fix is very different.

Hidden debris sources: leaves in the system, clogged lines, or neglected covers

Sometimes the pool looks cloudy because it’s constantly being re-contaminated. A clogged skimmer line, a neglected cover full of sludge, or debris sitting in an overflow channel can keep feeding fine particles back into the water.

Check the basics: skimmer baskets, pump basket, cleaner bags, and any in-floor system screens. If you have a cover, clean it and the surrounding deck so you’re not washing grime into the pool every time it rains.

Cloudiness that “never ends” often has a continuous source. Finding and stopping that source is the real win.

Cloudy water in new pools (and why it’s common)

New pools—especially freshly filled ones—often go through a cloudy phase. That doesn’t mean something is wrong, but it does mean you need to be proactive early on so the water doesn’t spiral into algae or scale.

Fresh fill water can have metals, high calcium, or high alkalinity depending on the local water supply. New plaster can also affect pH and alkalinity as it cures, and dust from construction can linger in the water.

Startup chemistry and curing effects

In plaster pools, pH can rise frequently during the early curing period, and that can contribute to haziness if it’s not managed. Brushing is also critical during startup to remove plaster dust and help the surface cure evenly.

Even for vinyl or fiberglass pools, startup is when people are most likely to overshoot chemicals. It’s easy to get excited and “correct everything at once,” which can create precipitation or sanitizer instability.

If your pool is newly built and you’re dealing with cloudy water, it’s worth following a structured startup plan provided by your builder or service team rather than improvising.

Construction debris and fine particulates

Even after a thorough cleanup, new pools can have fine dust in the system—especially if landscaping and hardscaping are still being finished nearby. Wind and rain can wash more dust in.

The fix is mostly mechanical: longer filtration, more frequent filter cleaning, and consistent brushing. Clarifier can help if the pool is sanitized and balanced, but it’s usually not necessary if you give the filter time and keep the water in range.

If you’re planning a build or you’re in that early ownership window, working with a team experienced in pool installation in Greenville, DE (or your local equivalent) can make the startup period feel a lot less mysterious.

Cloudy water in salt pools: what’s different?

Saltwater pools can absolutely get cloudy, and the causes are mostly the same: low effective chlorine, high pH, filtration limits, and organics. The difference is that salt systems (SWGs) tend to push pH upward over time, and they produce chlorine slowly rather than all at once.

That means you can end up with a pool that’s “usually fine” but turns cloudy during heat waves, after storms, or when bather load spikes—because the generator can’t keep up quickly enough.

Check SWG output and runtime

If your water is cloudy and you have a salt system, verify that the cell is clean, the salt level is correct, and the output percentage is appropriate for the season. Also verify that the pump is running long enough for the cell to generate the chlorine you need.

Many owners solve cloudy episodes by temporarily supplementing with liquid chlorine while keeping the SWG running. That gives you an immediate sanitizer boost without waiting days for production to catch up.

Also keep an eye on CYA: salt pools often run a bit higher CYA to protect chlorine, but if it climbs too high, you can end up under-chlorinating without realizing it.

Stay ahead of pH drift

Because SWGs tend to raise pH, cloudy water can show up when pH creeps up and chlorine becomes less effective (and calcium is more likely to precipitate). Testing pH more frequently—especially in peak season—prevents that slow slide into haze.

If you’re constantly adding acid, your TA may be too high for a salt pool. Adjusting TA to a more appropriate range can reduce pH rise and stabilize clarity.

A small change in routine—like checking pH twice a week—can prevent weeks of cloudiness battles.

Cloudy water and metals: when it’s not algae or filter fines

Metals like iron and copper can cause discoloration and haze, especially after shocking. Sometimes the water looks cloudy with a faint tint (yellow/brown/green) that doesn’t behave like algae. Metals can enter from well water, corroding heaters, or certain algaecides.

If you suspect metals, don’t keep shocking blindly. High chlorine can oxidize metals and make the water look worse temporarily.

How to spot metal-related cloudiness

Clues include: stains on steps or liners, tinted water that doesn’t respond to algae treatment, or cloudiness that appears quickly after adding chlorine. A metal test (pool store or home kit) can confirm.

If metals are present, a sequestrant can keep them dissolved and reduce staining. Long term, you may need to address the source (like heater corrosion or metal-rich fill water).

Metal issues are manageable, but they require a different playbook than algae or filtration.

Be careful with copper-based algaecides

Copper can help control algae, but it can also stain surfaces and contribute to water tinting when chemistry swings. If you’ve been using copper products regularly and you’re seeing strange haze or staining, it may be time to change strategies.

Most pools can stay algae-free with properly managed chlorine and circulation without relying heavily on copper additives.

If you’re unsure what’s in your products, check labels—cloudiness troubleshooting gets much easier when you know what you’ve been adding.

A practical “clear water” routine that prevents cloudiness

Once your pool is clear again, keeping it that way is mostly about consistency. The goal is to prevent small issues from stacking up until your pool looks dull.

Here’s a routine that works for a lot of pool owners, with room to adjust based on your climate and bather load.

Weekly habits that pay off

Test FC and pH at least 2–3 times per week in summer (more if the pool is heavily used). Test TA, CYA, and CH weekly or biweekly depending on how stable your water is. The more stable your pool, the less you have to chase it.

Brush walls and steps weekly, even if the pool looks clean. This prevents biofilm and keeps fine debris from sticking. Skim as needed and empty baskets before they’re packed.

Check filter pressure and clean/backwash when it rises 20–25% above clean pressure. Don’t wait until flow is obviously weak.

After-party and after-storm protocol

After a big swim day, run the pump longer that night, brush quickly, and make sure chlorine doesn’t dip too low. If you know you’re hosting, raise chlorine slightly beforehand (within safe ranges) so you have a buffer.

After storms, remove debris ASAP, test and adjust chlorine and pH, and give the filter extra runtime. It’s much easier to prevent a cloudy bloom than to clear one.

These two moments—parties and storms—are when most “random” cloudiness starts.

Seasonal resets that keep you out of trouble

At the start of the season, do a full panel test including CYA and CH. If CYA has crept up over the years, plan a partial water replacement before the hottest weather arrives.

Mid-season, consider a deeper filter service: soak cartridges, inspect DE grids, or evaluate sand condition. A filter that’s been “kind of okay” for years can suddenly become the reason your pool won’t clear.

If you ever feel like you’re doing everything right but the pool still won’t cooperate, a check-in with a trusted swimming pool company in Bear, DE (or a qualified local pro) can help you spot problems you can’t see—like failing media, suction leaks, or circulation design issues.

Common mistakes that keep pools cloudy (even with “good” effort)

A lot of cloudy pools aren’t neglected—they’re just caught in a loop of well-intended mistakes. If you recognize any of these, don’t worry. Fixing the pattern is usually easier than fixing the water was.

Adding multiple chemicals back-to-back without retesting

It’s easy to panic and add pH down, then alkalinity up, then shock, then clarifier—often within an hour. That can create chemical conflicts and make water cloudier through precipitation or temporary imbalance.

Instead, make one adjustment, circulate, retest, then decide the next move. Pool water responds with a delay, and giving it time prevents overcorrection.

If you’re ever unsure, prioritize pH and chlorine first. Those two solve the majority of clarity issues.

Relying on “perfect” numbers from strips alone

Test strips are convenient, but they can be inconsistent—especially for CYA and sometimes chlorine at higher levels. If you’re troubleshooting cloudiness, accuracy matters.

A drop-based kit (or a digital photometer) gives you better data, which leads to fewer chemicals and faster results. Many people are shocked (no pun intended) by how different their real CYA is from what strips suggested.

Better testing is often the cheapest upgrade you can make to your pool routine.

Ignoring the filter because “chemicals should fix it”

Chemicals sanitize and balance, but they don’t remove physical particles. That’s the filter’s job. If your pool is cloudy from dead algae or fine debris, you can have perfect chemistry and still have bad clarity until filtration catches up.

When in doubt: clean the filter, brush, and run the pump longer. Those steps are boring, but they’re what turn cloudy water into clear water.

And if the filter can’t keep up even when clean, that’s a sign it may be undersized or worn out.

A quick troubleshooting map you can use anytime

If you want a simple way to decide what to do next, use this mental flow:

If the pool is cloudy and greenish: treat as algae (raise/maintain chlorine for CYA, brush, run filter nonstop, clean filter often).

If the pool is cloudy and milky white: check pH/TA/CH and filter condition; lower pH if high; clean filter; consider fine-particle filtration help only after balance is corrected.

If the pool is cloudy after a storm or party: remove debris, bump chlorine, extend filtration, and clean the filter.

If the pool is cloudy after adding chemicals: improve circulation, retest, correct pH, and avoid stacking incompatible adjustments.

Cloudiness feels complicated, but it usually becomes obvious once you match what you see to what your test results say.