Frequently Asked Questions

Get answers to common questions about AquaChek products. Or, you may contact us to ask a question.

Order a replacement color chart for your AquaChek Select 7-in-1 Complete Pool Care Kit.


I am getting different readings when testing with my TruTest meter. Does my meter need to be recalibrated or what could cause the difference in my readings?

The TruTest meter comes with a factory set calibration and will last for the life of the meter. When taking measurements with your TruTest meter it is expected that there will be some slight variation between readings. The readings you receive should be equal to the accuracy of reading a visual test strip.

However, if your readings are erratic, below are some troubleshooting guidelines you can use to improve your readings:

  • Make sure you are using TruTest test strips.
  • Gently shake the water off the test strip before placing in the meter. Do not wipe off with fingers.
  • Lay the strip on the test screen, do not slide strip in—place the first pad (nearest the top of the strip) onto the window first, then lower the rest of the strip down onto the window.
  • Use the sun shield (or use your hand to shade the strip during the reading).
  • Use your cleaning tool or a cotton swab and lightly tap the back of the test strip to ensure the test pads are making proper contact with the testing window on your meter.
  • Make sure there are no scratches on the testing window and the glass is clean—any residual from previous tests can cross-contaminate the new pads leading to inconsistent test results.
  • Clean the window using the provided swab or a Q-tip ensuring the pad makes contact with the testing window. See ‘How should I clean my TruTest meter’ in the FAQs for more detail.
  • Store test strips in a cool, dry place and avoid touching the test strip pads prior to testing as this could affect results. It is important to keep the lid of your pool/spa test strips bottle securely tightened when not in use.

You can also watch our instructional video for your TruTest meter.

I am getting an ER2 message on my TruTest Meter, what should I do?

The cause of the ER2 error is likely excessive light entering the system and interfering with the operation. To protect against this, try shielding the strip window with your hand or use a blocking cover to block the light.  To receive a cover that can be connected to the wrist strap of the meter for convenient use, send us an email at aquachek@hach.com with the word "cover" in the subject line.

I’m getting a "LO" on ALK and no value for pH or CL on my TruTest meter. Is this an error? My chemical test kit says Cl is fine and the pH is out of range.

When "LO" appears in the area where total alkalinity results should appear, the battery voltage/power is low. In this case, replacing with fresh batteries will correct the issue.

How should I clean my TruTest meter?

A simple, non-abrasive wiping of the test strip window and all other surfaces with clean, fresh water should clear any residual chemicals remaining from pool testing.

Should I "place" or "slide" the TruTest test strip onto the TruTest Reader strip window?

It is very important that you DO NOT SLIDE the test strip onto the window. This action will result in inaccurate readings. A simple method is to place the first pad (nearest the top of the strip) onto the window first, then lower the rest of the strip down onto the window. This will ensure the strip is correctly placed in the window.

What will happen if my TruTest meter falls into my pool or spa?

The meter was designed to withstand this kind of accidental submersion and will float when it hits the water. Simply remove the meter, take out the batteries from the battery compartment, dry the compartment thoroughly, and replace with dry batteries. The meter should return to full performance.

I need a new battery clip for my TruTest Meter, how do I get one?

Please contact us via email at aquachek@hach.com to request a replacement. Include your name and mailing address with your request for new battery clips.

I have the AquaChek TruTest “blue” meter which is for chlorine, but I use bromine in my spa. Is there a conversion or multiplier to calculate/convert the chlorine "CL" reading to bromine?

When using the TruTest Digital Test Strip reader in bromine pools or spas, the display value for chlorine can be multiplied by 2.2 to convert it to a bromine value.

Can I use the TruTest meter in a pool/spa that has a salt generator?

Both the blue and red TruTest meters can be used in pools/spas equipped with salt systems. Note that they will not work for extremely high-salt specialty applications such as float tanks.

What is the difference between the TruTest Spa (Red) tester and the regular TruTest (Blue) tester?

The blue TruTest meter gives digital results for Free Chlorine, pH and Total Alkalinity while the red TruTest Spa meter gives digital results for Total Bromine, pH and Total Alkalinity. If using bromine as your sanitizer choose the red meter, or if using chlorine as your sanitizer choose the blue meter.

Test Strips

Do test strips really work?

Yes. Test strips were developed for the medical industry in the 1960s to be used as diagnostic tools. They have since replaced liquid reagent tests for urine and blood testing and are used in a number of other industries as well. AquaChek test strips use this same trusted technology to provide accurate results regarding water contaminants.

How accurate are test strips?

Test strips offer comparable accuracy to liquid color comparator tests. You may find that results are even more accurate because liquid kits require measuring samples and counting drops of reagent which leaves more room for human error.

What is the shelf life?

Most AquaChek products are good for at least 24 months from the date of manufacture. Each bottle of AquaChek test strips is clearly marked with an expiration date. We cannot guarantee the accuracy of the test strips beyond the expiration date on the bottle and therefore recommend replacing out-of-date strips. Storage in high heat or humid conditions will shorten expected shelf life. Ideal storage conditions are noted on the bottle.

What is the difference between AquaChek and the other pool and spa test strips available on the market?

AquaChek has been the top-selling brand of pool and spa test strips in the world since the early 1980's. Experience as well as continued product improvement keeps AquaChek ahead of the competition.

What is the best way to care for my AquaChek Strip kit?

Store your test kit in a cool, dry place and avoid touching the test strip pads prior to testing as this could affect results. It is important to keep the lid of your pool/spa test strips bottle securely tightened when not in use and not to remove the desiccant (moisture protection pillow) in the test strip bottle.

One of the test pads on the strip doesn't match the color chart. What might be happening?

Chemistry Pad Color What could this indicate?
Free Chlorine Pink This may be due to high acid or high base conditions. Check the pH and Total Alkalinity levels to see if they are very high or very low.
Total Chlorine/ Total Bromine Brown or Orange The bromine level or chlorine level is higher than 20ppm which is very high. Remove any bromine tablets from your pool or spa until the level is back in the “ok” range.
pH Bright Yellow The pH level is very low — it is urgent to bring the pH back up into the “ok” range. A low pH can cause swimmer discomfort in the skin and eyes and can cause corrosion of pool fixtures and equipment, leading to costly repairs. Please refer to a pool professional or AquaChek calculators for assistance in raising or lowering pH levels.
Light Pink A pink color on the pH pad can be caused by a very high sanitizer level. Additionally, at high pH, the pH pad can be a pink/violet color.
Black The pH pad can turn black when being dipped into spas with high concentrations of Bromine sanitizer.
Purple The sanitizer level (chlorine or bromine) is very high and needs to be brought down to the "ok" range, and then retested for pH and Total Alkalinity. An excess of chlorine can bleach hair or bathing suits and can cause eye irritation.
Cyanuric Acid Yellow A yellow color for stabilizer can be caused by a few different conditions. Usually, things like low pH and low alkalinity can cause the stabilizer pad to be yellow. For the best stabilizer results, it should be used in water that has pH between 7.0-8.4 and total alkalinity of 240 ppm or lower.
Total Alkalinity Royal Blue There are two possibilities: (1) If your pH pad turned purple as well, the sanitizer level is probably very high. Lower the sanitizer and then retest. (2) If your pH pad did not turn purple, the total alkalinity level is high (about 300ppm). Lower the total alkalinity and then retest. Remember, if your cyanuric acid level is high, it can contribute up to 1/3 of the total alkalinity reading.

I purchased an AquaChek product but have lost the color block comparison chart or it has faded. How do I get another chart?

Request a replacement chart which will be sent to you in the mail.

How do I read the salt level on the AquaChek Pool & Spa Salt Titrators?

First, fill a small vial with about one inch of pool or spa water, then remove a strip from the bottle (replacing the cap immediately). Insert the lower end of the strip into the water, making sure NOT to immerse the yellow completion band at the top of the strip. The strip should remain in the water until the test is complete (when yellow band turns dark, typically 3-4 minutes). Note where the top of the white peak falls on the number scale; read the top of the peak to the nearest 0.2 division. Next, locate the sodium chloride concentration next to that reading on the table printed on the AquaChek White bottle. Or watch this quick product demo for AquaChek Salt.

What is the difference between the red test strips and the yellow test strips?

"Red" test strips are for testing bromine and "yellow" test strips are for testing chlorine.

Do you have an online (pdf) copy of product manuals?

PDF's of product inserts are available on our website. Please go to our Home Owners page and then click on the product you are interested in. Once the product page loads, click on the "Manual" link to view the PDF.

How far do I need to submerge the test strip in my pool water?

Dip the strip far enough down in the water, and away from jets (moving water), to ensure the pads are fully saturated.

I am using AquaChek test strips and noticed I get a different reading on the test strip when I wait several minutes to read it rather than waiting 15 seconds like the instructions indicate. Which timing is most accurate?

The test strips use a color chart that has color blocks matched or calibrated to the timing instruction listed on the product. The reactions should be compared after the amount of time listed on the label and not later, even if the colors continue to change.

The test strip chart on the bottle of the salt test strips does not correspond to the chart used in the You Tube video. Do the charts on the bottle only correspond to the test strips from the bottle they came in?

The test strip chart on each bottle of the salt test strips is calibrated for each lot of product. The chart on the container should be used only with the strips that come inside it.

The free chlorine pad on my AquaChek test strip turned pink. What does this mean?

This may be due to high acid or high base conditions. Check the pH and Total Alkalinity levels to see if they are very high or very low.

Is it possible to reuse test strips several times (two or more times)?

It is not possible to use the test strips again after they have been wetted with water. The chemistry is depleted after the first use and the test strip should be discarded.

I just opened a bottle of AquaCheck test strips and wanted to know if the pads on the strip should be white before use?

Test pads on the test strips contain reagents, which may be white or have some color to them. Once the test strip has been dripped into pool water it will react and change color intensity to indicate concentrations for the different parameters.

Where can I buy refill test strips for the AquaChek TruTest or AquaChek Select test kit?

You may want to check with your local pool or spa retailers to see if they carry the refill sku. Many online retailers sell these products as well.

Can I use AquaChek test strips in a pool/spa that has a salt generator?

AquaChek test strips can be used in pools or spas equipped with salt systems. Note that they will not work for extremely high-salt specialty applications such as float tanks.

How do I request an SDS or MSDS?

You can request an SDS or MSDS by filling out our contact form. Remember to include product number(s) and country(s) where product is used so the request can be processed.

Which AquaChek products can be used with salt pools (pools equipped with salt generators)?

Our line of AquaChek pool and spa test strips as well as the AquaChek TruTest meters can be used in pools that have salt generators.

Smart App

Which chlorine type do I select in the system set up page of the app if I have a salt chlorine generator system?

The type of chlorine that is being generated from the electrolytic cell on the generator is hypochlorous acid, or liquid chlorine. Chose this chlorine type in the app. If the prescription calls for more to be added, you would need to turn your generator to increase the chlorine production/concentration. Alternatively, you could add some liquid chlorine to boost/supplement the cell's output.

Pool Chemistry

What is the difference between free and total chlorine?

Free chlorine refers to both hypochlorous acid (HOCl) and the hypochlorite (OCl-) ion, or bleach, and is commonly added to water systems to sanitize, disinfect, and oxidize. When ammonia or organic nitrogen are introduced to the water through contaminants like sweat or organic materials, the chloramines known as monochloramine, dichloramine, and trichloramine will quickly form. Chloramines are also known as combined chlorine.

Total chlorine is the sum of free chlorine and combined chlorine. The level of total chlorine will always be higher than, or equal to, the level of free chlorine. If the total chlorine level exceeds the free chlorine level a super chlorination or "shock" is needed. If the pool water has a strong, offensive odor and is irritating the skin or eyes of the swimmers that may be a sign that you need to “shock” the pool to remove the total chlorine.

In short, free chlorine is chlorine that is available and ready to help keep your pool water clean. Combined chlorine has been “used up” and will no longer help with sanitizing your water. Total chlorine is the sum of both the free chlorine and the combined chlorine.

How do I decrease the Free Chlorine level if it’s too high?

To decrease Free Chlorine you can partially drain and refill your water, but this will affect the rest of your pool parameters as well. Another method is to add sodium thiosulfate to lower the Free chlorine concentration. Lastly, Free chlorine levels will dissipate over time. If the water is covered you can expose it to sunlight which will speed up the degradation of the Free Chlorine.

How often should I test my Pool or Spa?

You should test your pool or spa a minimum of 2-3 times per week. A spa should be tested before each use due to the higher water temperature and smaller water volume. Pool and spa testing is also advised after heavy swimmer use (i.e. a party), after animals have been in the pool, after a heavy rain, after fertilizing, etc. It is also advised to test your pool or spa 24-48 hours after chemicals have been added to ensure accuracy in rebalancing.

What is pH?

pH is the intensity of acid or alkaline materials in the water of your pool or spa.

What can cause pH levels to fluctuate?

Many things can cause pH levels to change including rainfall, dust, organic materials, covering your pool, or using various pool additives.

What is total alkalinity?

Total alkalinity measures the amount of alkaline substances (primarily bicarbonates and carbonates) in your water. Alkaline substances buffer your water against sudden changes in pH so that your water chemistry is more easily controlled.

What is cyanuric acid (stabilizer)?

Cyanuric acid (sometimes called stabilizer or conditioner) makes chlorine more stable in the sun's UV rays, acting like a sunblock for your sanitizer by keeping it from degrading as quickly as it would otherwise. If the cyanuric acid is too low the chlorine levels can drop from an ideal range to zero in less than two hours. If cyanuric acid levels are too high, the chlorine will become less efficient. It is important to maintain cyanuric acid in the recommended range.

What is total hardness?

Total hardness refers to the amount of calcium or magnesium in your pool or spa water. When total hardness is too high scale can form causing pool filters or plumbing to clog and the water to appear cloudy. If water is too soft, or low in total hardness, it will become aggressive and slowly dissolve plaster walls and corrode metal fixtures. Swimming pools and spas should have a total hardness of 250-500ppm.

What is algae and why is it in my pool?

Algae are microscopic plants which can grow in your pool or spa. They obtain their nutrients from leaves, plants and other organic matter (including swimmers). Algae can be caused by one or more of the following: no available free chlorine, poor or inadequate filtration, poor circulation (leaving "dead zones" of stagnant water), elevated phosphates in the water, incorrect pH levels, too much cyanuric acid/stabilizer, or failing to test pool water regularly and adjust parameters.

How can I treat algae in my pool?

The treatment of algae depends on the type present in the water (black, green or yellow). Most algae blooms can be addressed with algaecide and/or shock treatment. However, this does not effectively treat all algae. We suggest consulting with your pool or spa professional for treatment recommendations.

What are phosphates?

Phosphates are a main food source for algae and other plant life, and are present in most plant and lawn fertilizers. Phosphates can be introduced to your pool or spa from various sources including fertilizer overspray or leaching, plant remnants (such as leaves or grass clippings), animals in the water, precipitation, or the source water that is used to fill your swimming pool or spa.

My water has a foul, strong odor and when my kids swim they complain of itchy skin and burning eyes. What could be wrong with the water?

There may be a high level of combined chlorine and/or a very low level of free chlorine. The first step is to get the pH level back in the ideal range of 7.2-7.8 ppm for a pool. Secondly, add additional chlorine or non-cholorine shock to eliminate combined chlorine. Swimmers can use the pool again once the free chlorine levels drop below 5 ppm.

What is scale formation?

Scale formations are crusty, white deposits on pool surfaces that signal a high level of pH, calcium hardness, total alkalinity, or low levels of hardness. The deposits can make the pool surfaces rough and also decrease the water flow through the filter and plumbing systems. The first step is to decrease pH and total alkalinity then adjust the calcium hardness.

Why is my pool or spa water cloudy?

There are several reasons why pool or spa water can be cloudy: no free chlorine available, incorrect pH or total alkalinity, inadequate filtration, or an algae infestation.

How do I clean my filtration system to see if it is causing cloudy water?

It is recommended to backwash the system first to see if this adjusts the pressure back to normal operational level, then clean the filter according to manufacturer directions. If you have additional questions regarding filter maintenance please consult your local pool or spa professional.

Why add chlorine to a salt water pool?

A salt-water chlorinator is designed to maintain residual chlorine by dosing small amounts of chlorine into the water when the filtrating system is on. The chlorinator may struggle to keep up and maintain those residual levels during times of heavy use, the cell needs cleaning, heated pool water, or inadequate amounts of cyanuric acid/stabilizer acid levels. The extra dose of chlorine can help the chlorinator during those conditions.

I have a salt water pool, how do I determine if I have the right amount of salt in my pool?

AquaChek White salt titrators will help determine the actual level. Compare the test results to the manufacturer's suggested level in your salt chlorine generator owner's manual.

Can I use chlorine in my biguanide pool?

No, never use chlorine in a biguanide pool.

If the Total Hardness level is high, what can be done to reduce the hardness level?

Depending on how high the hardness level is, you could do a partial drain or complete drain and then refill with a source water that has a lower hardness level.

What does the acronym TDS stand for?

TDS is Total Dissolved Solids, defined as all inorganic and organic materials dissolved in water. If it is too high, cloudy water can present itself.

Do you have an online calculator where I can put my test results in and tell me what needs to be added to the pool?

Yes, you can access our online calculators. If you have a smartphone, you can also download the AquaChek Smart app which simplifies management of test results and provides prescription advice.

Are chlorine and bleach the same thing?

Bleach contains chlorine in the form of hypochlorous acid, "free chlorine." Typically, it is at a level of 4 to 6% hypochlorous acid.

Why do I get different readings when I test the water in different spots? Is one spot better than another for testing the pool water?

It is recommended by most pool professionals to test the water at several locations of your pool, at least at both ends. Differences can be cause by inadequate filtration or circulation, and differences in water depth.

What is the best sequence for balancing pool water (PH or alkilinity first etc.)

Before you attempt to balance pool or spa water, you need to establish a minimum level of calcium hardness. The next pool water condition to be adjusted should be total alkalinity. Then adjust the pH level. Finally, adjust the sanitizer level (such as free chlorine or bromine)

How do you establish or increase the cyanuric acid level (stabilizer)?

For establishing or increasing cyanuric acid (stabilizer) levels, please refer to the CYANURIC ACID chart in the AquaChek Yellow product insert.

I am testing my pool at both ends as recommended but I'm getting different chlorine readings. What should I do?

If the results are different from testing at both ends, it is an indication of improper or insufficient circulation of the water. The pump, circulation, etc., should be checked and/or increased.

Service Pros

What information supports the accuracy of test strips?

AquaChek test strips are manufactured and released against standard reference procedures from the 17th Edition of Standard Methods for the Examination of Water and Waste Water.

Why aren’t there more values on the color charts for AquaChek products?

AquaChek products are designed to be user-friendly. To make them easy to use and understand, we ensure that color values can be clearly differentiated so accurate decisions can be made regarding water treatments.

What is the difference between AquaChek and the other pool and spa test strips available on the market?

AquaChek is the top-selling brand of pool and spa test strips in the world. AquaChek test strips undergo stringent release qualification. Constant monitoring of the manufacturing process ensures that the finest test strips are available for your use. Our company has earned the internationally recognized ISO 9001 certification for following strict quality standards.

My liquid DPD test kit shows I have 3 ppm free chlorine while my AquaChek test strips say I have 0 ppm free chlorine. Which test is correct?

If there is a high level of combined chlorine in your pool or spa, it is likely the DPD test is showing a false positive for free chlorine and your AquaChek Pool & Spa Test Strips are giving an accurate reading. For more detailed information, please visit the following Free Chlorine Testing Technical Bulletin.

Are liquid DPD kits more accurate?

Liquid DPD tests for chlorine can be affected by interferences, such as an over-abundance of monochloramines or potassium monopersulfate (used for shock-treating pools). These can give a false positive reading for free chlorine with the DPD liquid tests. Recognized technical studies are available to support these claims. In addition, the liquid DPD test requires careful technique and several steps to get the best results.

What is test strip shelf life?

We ship most of our products with a 24-month shelf life, at a minimum. A few of our specialty products, such as test strips for iron and copper have no less than an 18-month shelf life. Each bottle is noted with an expiration date. Even though the effectiveness of all liquid test reagents and test strips degrade over time, some of our competitors do not date their product. Dating the product is just one way AquaChek ensures product performance and quality.

How accurate are the test strips?

Test strips are at a minimum comparable in accuracy to liquid color comparator tests. AquaChek strips are more convenient and we believe they actually deliver greater accuracy. The strips reduce the chances for human error associated with liquid kits, which require measuring samples and counting drops of reagent.

I have added a significant amount of Chlorine and the AquaChek test strips still read 0 ppm for Free Chlorine-why?

If testing for free chlorine using a DPD liquid test kit, be aware that high levels of combined chlorine, or chloramines, can cause false positives when using DPD #1 test for free chlorine. In order to confirm this is taking place, take a small sample (3-4 cups of water) out of the pool. Add a small amount of chlorine (e.g. a teaspoon of bleach or several dichlor granules) directly to the sample to be sure that chlorine residual can be established. You should be able to measure the free chlorine right in the sample almost immediately after the chlorine has been added. This is representative of the rest of the pool. If chlorine residual can be established in a small sample, then you will know that the actual pool can be treated in the same way. Additionally, the DPD or OTO test will measure the same as the strips at this point confirming that the combined chlorine was causing a false reading for the liquid/tablet test.