How to Test Your Pool Water

Quick Answer

Test your pool water 2-3 times per week during swim season using either a liquid drop test kit (Taylor K-2006 — the gold standard) or reliable test strips. Test for free chlorine and pH every time. Test alkalinity, CYA, and calcium hardness weekly or monthly. Dip or collect your sample from elbow depth, away from return jets, and at least 30 minutes after adding any chemicals. A good test kit costs $30-$80 and is the single most important tool you’ll own as a pool owner.

What You Need To Know

Step 1: Choose Your Testing Method

There are three ways to test pool water. Here’s the honest breakdown:

Method	Accuracy	Cost	Best For
Liquid drop test kit (DPD/FAS)	Excellent	$50–$80	Any pool owner who wants reliable results
Test strips	Good (varies by brand)	$10–$25 per bottle	Quick daily checks or as a backup method
Pool store testing	Variable	Free	Monthly cross-check only

Pro Tip: The Taylor K-2006 (or its clone, the TF-100 from TFTestKits.com) is recommended by nearly every pool professional and enthusiast community. It uses the FAS-DPD method for chlorine, which gives you an exact number rather than a color match. It’s worth the $50-80 investment — bad test results lead to bad chemical additions, wasted money, and water problems that didn’t need to happen.

Step 2: Collect a Good Sample

Where and how you get your water sample matters more than you’d think.

How to do it right:

Turn the sample cup or vial upside down and push it into the water
Go elbow deep — about 12-18 inches below the surface
Point the opening away from return jets and away from the skimmer
Flip the cup right-side up underwater, then pull it out

Why this matters:

Surface water gets hit by UV and loses chlorine faster — not representative of your whole pool
Near return jets gets recently filtered/treated water — reads artificially clean
Near the skimmer gets untreated incoming water — reads artificially dirty
Mid-pool, elbow deep gives you the most representative sample

Step 3: Run Your Tests

Using a liquid drop kit (Taylor K-2006 or TF-100):

Free Chlorine (FC): Fill the large comparator tube to the 25 mL mark. Add the FAS-DPD reagent (R-0870) — 5 drops. Water turns pink. Now add R-0871 one drop at a time, swirling after each drop. Count the drops until the pink disappears. Each drop = 0.5 ppm of free chlorine
pH: Fill the small comparator tube to the mark. Add 5 drops of R-0014. Compare the color to the chart. Yellow = low, orange = 7.2-7.6, red = high
Total Alkalinity: Fill the tube to the mark. Add 2 drops of R-0007 (green to blue color), then add R-0008 drop by drop. Count drops until the color changes from green to red. Multiply drops × 10 = alkalinity in ppm
CYA (Cyanuric Acid): Mix equal parts pool water and R-0013 reagent. Look through the tube at the black dot. Note where the dot disappears — that level on the tube = your CYA in ppm
Calcium Hardness: Fill to mark. Add reagents per instructions. Count drops until the color change. Calculate per the chart

Using test strips:

Dip the strip into elbow-depth water for 2 seconds, don’t swirl it
Remove and hold it level (don’t shake off excess water)
Wait the time specified on the bottle — usually 15-30 seconds for most pads, up to 60 seconds for CYA
Compare colors to the chart on the bottle while the strip is still wet
Read in good natural light, not under yellow indoor lighting

Step 4: Know What to Test and When

Test	Target Range	Frequency	Why It Matters
Free Chlorine	2-4 ppm (varies with CYA)	2-3x per week	Sanitizer — kills bacteria and algae
pH	7.4–7.6	2-3x per week	Comfort + chlorine effectiveness
Total Alkalinity	80–120 ppm	Weekly	Stabilizes pH
Cyanuric Acid (CYA)	30–50 ppm (chlorine) / 60-80 ppm (salt)	Monthly	Protects chlorine from UV
Calcium Hardness	200–400 ppm	Monthly	Protects pool surfaces
Combined Chlorine (CC)	0 ppm (under 0.5)	Weekly	Indicates chloramines (the “chlorine smell”)

Pro Tip: Your minimum chlorine level depends on your CYA level, not a fixed number. The rule of thumb: FC should be at least 7.5% of your CYA. So if CYA is 40 ppm, keep FC at 3 ppm minimum. If CYA is 80 ppm, you need FC at 6 ppm minimum. This is why keeping CYA in check matters so much — high CYA demands high chlorine.

Deep Dive

Liquid Drop Kit vs. Test Strips — The Real Difference

Test strips measure by color comparison, which introduces human error and is affected by lighting, strip age, and moisture exposure. They’ll get you in the ballpark — close enough for a quick “is everything roughly OK?” check.

The FAS-DPD method used in the Taylor K-2006 (and TF-100) is different. Instead of matching colors, you count drops. The pink either disappears or it doesn’t — there’s no ambiguity. This gives you precision to 0.5 ppm for chlorine and 10 ppm for alkalinity. When you’re trying to decide whether to add 4 oz of acid or 12 oz, that precision matters.

The practical compromise: Use a liquid drop kit for your thorough weekly test (FC, pH, TA, CC). Use test strips for quick mid-week FC/pH checks. Use the pool store for a monthly cross-reference (and say “no thanks” to whatever they try to sell you based on the results).

How to Take a Water Sample to the Pool Store

If you bring a sample to the pool store, follow these rules:

Use a clean plastic container — rinsed with pool water, not tap water
Collect the sample as described above (elbow deep, away from returns)
Bring it within 30 minutes. Chlorine off-gasses quickly — an hour-old sample will read lower than your actual pool
Do not leave it in a hot car
Know that pool store testing machines (like the Lamotte Spin system) are generally accurate, but the recommendations they give are often designed to sell products. Trust the numbers, be skeptical of the advice

When to Test More Frequently

Bump up to daily testing when:

You’ve just filled or partially drained the pool
After a heavy rain (rain dilutes chemicals and drops pH/alkalinity)
After a pool party (heavy bather load uses up chlorine fast)
After adding a large chemical dose (verify it hit the target)
If the water looks or smells “off” in any way
During spring opening — test daily for the first week until levels stabilize
After an algae treatment — monitor FC closely during the kill and clean process

Understanding Combined Chlorine

Your test kit measures Free Chlorine (FC) — the chlorine available to sanitize — and Total Chlorine (TC). The difference between them is Combined Chlorine (CC):

CC = TC − FC

Combined chlorine is “used up” chlorine — chloramines — that’s bonded with nitrogen compounds (sweat, urine, body oils). This is what creates that harsh “chlorine smell” at public pools. A clean pool with proper chlorine should have almost no smell.

CC = 0: Ideal. Your chlorine is doing its job efficiently
CC under 0.5 ppm: Acceptable
CC above 0.5 ppm: Time to shock the pool (superchlorinate to break apart the chloramines)

Reagent Care and Shelf Life

Your test results are only as good as your reagents:

Store all reagents out of direct sunlight and in a cool place (not in the pool shed that hits 130°F in summer)
Most liquid reagents last 1-2 years from manufacture. The DPD powder reagent (R-0870/R-0871) is the most sensitive — replace annually
Test strips have a shelf life printed on the bottle. Once opened, use within 90 days. Keep the cap tightly closed — moisture ruins them
Replace your Taylor kit reagents once a year at the start of pool season. You can buy just the reagent refills ($30-40) instead of a whole new kit
If your FAS-DPD test water doesn’t turn pink at all, your R-0870 is likely expired

💲 Cost Comparison: Taylor K-2006 complete kit: ~$80, annual reagent refills: ~$35. Test strips (100-count bottle): ~$15, using 3/week = $25/year. Pool store testing: free but costs gas and time. The best approach costs about $80 the first year and $35-50/year after that — less than one month of pool service.

Digital and Smart Testing Options

Several electronic testers and smart devices are available:

Electronic pH meters: Accurate but need calibration. The cheap $15 ones drift quickly. Decent ones (Apera, Hanna) start around $50-80
LaMotte ColorQ / Spin Lab: Tablet-based systems. Accurate and removes color-matching guesswork. $150-300
Smart probes (pHin, Sutro, WaterGuru): Continuous monitoring devices that sit in the pool. $150-250 + annual sensor costs. They’ll alert you via app when levels drift. Nice for busy owners, but they still need calibration and don’t replace occasional manual testing

For most pool owners, a $60-80 Taylor kit and a bottle of test strips is all you need. Fancy electronics are nice-to-haves, not must-haves.

FAQ

How often should I really test my pool?

During swim season: pH and free chlorine 2-3 times per week. Alkalinity weekly. CYA and calcium monthly. During winter (if you don’t close your pool): once a week for FC and pH is usually enough. If you have a salt system or chemical feeder, you can sometimes stretch to 2x/week since they provide continuous chlorine, but you still need to verify pH.

My test strip colors are between two shades. Which do I read?

This is exactly why test strips are less precise. If the color is between two shades, split the difference. For pH, that might mean you’re somewhere between 7.4 and 7.8 — a big range that could mean “perfect” or “needs acid.” This uncertainty is why a liquid drop kit is worth the money for your main weekly test.

Can I test pool water with a fish tank kit?

In a pinch, an aquarium pH test works fine — the chemistry is identical. But aquarium test kits don’t typically test for free chlorine, CYA, or calcium hardness, so they’re not a substitute for a proper pool test kit. Don’t try to use aquarium ammonia or nitrate tests for pool water — they’re testing for completely different things.

What does it mean when my test water turns really dark pink?

In the FAS-DPD chlorine test, very dark pink/magenta means your chlorine is high — possibly shock levels. Keep counting drops. It can take 20+ drops after a shock treatment. Each drop is still 0.5 ppm. If you lost count, dump and re-test.

Why do the pool store results differ from my home test?

Several reasons: time delay between collection and testing (chlorine drops), temperature difference, different testing methodology, or your reagents may be expired. Test at home immediately after collection for the most accurate results. Use the pool store as a rough second opinion, not gospel.