There are plenty of misconceptions about water chemistry and testing floating around. Aside from the one about a dye that will detect people peeing in the pool, which can be helpful if swimmers believe it, they all impede our ability to manage water quality. So let’s do some myth busting.
Myth 1: Experienced pool/spa operators can tell if there are issues with water quality by simply looking at the water
Coloured water, owing to dissolved metal or an algae bloom, and cloudy water do indeed signal trouble, but our goal is to nip problems in the bud before the water gets to this extreme. So is it true, “If it’s clear, have no fear?” Absolutely not; without routine water testing, inadequately sanitized water cannot be detected in time to protect swimmers from harmful microbes and unbalanced water cannot be detected in time to protect vessel surfaces and equipment from damage.
Myth 2: From a water maintenance perspective, a spa is basically a little pool
Understanding the uniqueness of a spa (i.e. its higher temperatures, smaller volume, jetted water and likelihood of high bather loads) is important to establishing usage rules and a proper cleaning, testing and treatment regime. These insights will also explain why the disinfection and water-testing regulations for public spas are even more stringent than those for public pools.
Water temperature is a factor
Pool water temperature is generally 26 to 29 C (78 to 84 F), while spa water runs between 36 to 40 C (96 to 104 F). Heated water, coupled with jet action, promotes a buildup of contaminants in the spa. Consider that, without enforcement, most people do not shower first, so whatever is on their skin ends up in the water—from natural body oil, lotions and perfume to grime, sloughed-off skin cells and what is politely known as ‘cheek wash.’ Further, it is estimated an adult will carry about one billion bacteria into the water, some potentially detrimental to health.
The most common spa-related ailments such as skin rashes and infections of the ear, urinary tract and cornea, are typically caused by the Pseudomonas aeruginosa bacteria. Legionella pneumophila is another bacteria found in spa water, which can be fatal to some individuals when inhaled with the aerosol from a spa. For most pathogenic bacteria, the optimal temperature for growth is between 37 to 40 C (99 to 104 F) (i.e. spa range). Certain bacteria populations can double in as little as 20 minutes if unchecked by a disinfectant. Harmful viruses, protozoans, yeasts and fungi shed into the spa and onto surrounding surfaces can also infect other users. Being immersed in hot water promotes sweating, and sweat contains some of the same metabolic wastes found in urine. In fact, I’ve read the average person will involuntarily release 50 mL (1.7 oz) of urine in addition to 200 mL (6.7 oz) of sweat during a 20-minute soak. The relatively small water volume of a spa means the chance of coming into contact with these contaminants, before they can be chemically destroyed or filtered out, is commensurately greater than in a pool.
Quicker chemical reactions
Hot water also speeds up chemical reactions. For every 10- C (18- F) increase in temperature, chemical reactions increase twofold. Between the heavy load of organic waste and the more dynamic chemistry, it is possible for two people in a 1,500-L (400-gal) spa to deplete a sanitizer level of two parts per million (ppm) bromine or one ppm free chlorine in just 15 minutes. (When you consider the people-to-water-volume ratio, those two folks in the spa is the rough equivalent to 1,250 people in a 1-million-litre (250,000-gal) public pool or 100 people in a 75,000-L (20,000-gal) residential pool!)
Beyond these health issues, spa operators must also be concerned about rapid changes in water chemistry, which affect both the efficacy of chlorine and water balance. For instance, aeration drives pH up. Potassium monopersulfate (MPS), the key ingredient in popular non-chlorine oxidizing shocks, will lower both pH and total alkalinity (TA).
Spa surfaces, plumbing and most especially the heater are at increased risk for scaling if the water becomes unbalanced. Calcium’s (Ca) solubility is inversely proportional to temperature—as water temperature increases, less calcium is able to stay dissolved, resulting in crusty deposits that will eventually lead to increased operating costs and expensive repairs.
Hot jetted water evaporates faster than cool, calm pool water, too, meaning total dissolved solids (TDS) will also build up faster in a spa and contribute to corrosion and cloudy water. Sanitizing with dichlor (C3HCl2N3O3), while convenient, pushes cyanuric acid (CNOH)3(stabilizer) levels beyond the recommended range of 25 to 50 ppm in very short order, making it hard for chlorine to do its job. It almost goes without saying, treatment chemicals must be administered very precisely in such small bodies of water—we call it ‘teaspoon chemistry.’
What does it all mean?
These unique characteristics mean spas require closer supervision of bather hygiene; a higher minimum level of sanitizer; more frequent testing, especially by commercial operators; more exact chemical treatment; frequent physical cleaning of the interior, deck and filtration system; plus periodic draining and refilling with fresh water.
If you are a spa dealer, customers will need some education from you to understand why they always should test sanitizer and pH levels before entering the spa.
Myth 3: Testing supplies are a commodity; therefore, a wise buyer shops on price
This myth is only embraced by newbies and people who service pools simply as a way station to another line of work. If you have been in business long enough you will come to know the hard way which testing equipment provides results you can confidently base your treatment decisions on. When determining which products have the right features for you and/or your customers, factors such as ease of use, completeness, accuracy and consistency and product availability should be considered.
Ease of use
Manufacturers carefully design test equipment to maximize service life and user productivity, such as withstanding repeated use in wet environments. Indicators of this are tear-resistant, waterproof instructions; vinyl, not paper, bottle labels; and desiccant inside test strip containers.
Other features to look for include products that are free of brittle plastic and small components that can be lost easily; no paper waste to dispose of after testing; and colour standards that are protected from bleaching or scratching. Further, fill marks on sample containers should be moulded, not painted on; and larger equipment cases should have handles.
Finally, kit components should also have a logical arrangement and be easy to take out and put back inside—it is a bonus if there is room in the case to store additional reagents or another small piece of equipment. It is also a big help if reagent caps are colour-coded to the instructions.
A good water analysis setup should offer:
- Comprehensive test instructions in simple language.
- A test for free chlorine covering the recommended range in a specific jurisdiction, and a way to determine combined chlorine (either by subtraction from a total chlorine reading or by a direct reading).
- A test for cyanuric acid, the stabilizer used in chlorinated outdoor pools/spas exposed to sunlight.
- A bromine test to service pools/spas treated with this sanitizer. (Note: the bromine value can be approximated by multiplying the chlorine reading by 2.25.)
- All the tests required to determine whether water is balanced, namely pH, total alkalinity and calcium hardness. (Note: a test for total hardness is not as appropriate, but it is the parameter most test strips offer.)
- Acid and base demand tests (liquid reagent kits) for making adjustments to pH.
- A device for calculating the Langelier Saturation Index (LSI) based on water balance readings.
- A summary of recommended ranges for each measurement (or a testing guide that goes beyond the bare minimum of recommended ranges to include helpful information like treatment tables).
- Technical support from the manufacturer.
Result accuracy and consistency
In order to calculate effective treatment chemical dosages, true readings for each test parameter are imperative. If you ever question the accuracy of your readings, use a standard solution, where the concentration of the analyte is already known, in place of your water sample. When proper water testing techniques are employed, the results should match the values printed on the labels of the standard solutions (plus/minus 10 per cent on the alkalinity [AT], hardness and cyanuric acid tests, and plus/minus 0.1 pH units on the pH test).
Make sure replacement reagents and parts are readily available, too.
Similar to any business expense, it pays to comparison shop using price as just one of several determining factors. The product with the best value for your needs may not be the cheapest. However, when compared to keeping swimmers healthy, protecting the client’s investment in the pools/spas under your care, and upholding your business reputation, reliable testing supplies are worth every penny.
Myth 4: Unlike liquid tests, test strips are so easy to use there is no such thing as proper technique
Granted, test strips are as simple a testing device as you are going to get, but they are not foolproof. Therefore, the following precautions must be taken:
- Limit the test strips’ exposure to air;
- Keep them dry before use;
- Do not contaminate the pads by touching them or setting them down on a dirty surface;
- Immerse as instructed. Dipping, swirling and swishing are different motions designed to expose the reagent pads to the water in a precise way for a specific time;
- Read instructions carefully, as some will say after wetting the pads to shake off the excess water, while others may warn against this;
- Let the correct amount of time elapse for starting and completing the readings;
- Read test values in the order given (those at the end of the sequence require the longest reaction time);
- Prevent reagents from running between pads by holding the test strip horizontal to the ground when comparing colours;
- Make colour matches in natural light, without sunglasses; and
- Do not use test strips past their expiration date.
Myth 5: Water samples can be taken from any convenient location in the pool
For your test results to be actionable, it is important to take a sample of water that is representative of the entire pool. Samples should not be taken from the water’s surface where it is interacting with the atmosphere, and possibly carrying debris and oils. Further, refrain from taking water samples from the immediate vicinity of a return line or chemical feeder, or in a dead zone (e.g. next to stairs) as these areas are also subject to special conditions.
When a pool has both shallow and deep ends, the sample should be taken midway between them using a clean plastic bottle. The bottle should be inserted into the water bottom-side up so the trapped air keeps out the water momentarily, then once at elbow depth, turn it right-side up and let it fill. If you just added a treatment chemical, allow at least two filtration cycles to pass to allow the chemical to circulate throughout the pool/spa before retesting the water.
Myth 6: Testing indoor/outdoor pools/spas is all the same
Ambient light is an important consideration in testing. Most manufacturers recommend performing colour-matching tests in natural light (but not looking into the sun). This is because artificial lighting will skew your colour perception—same with wearing sunglasses.
If finding natural light is inconvenient when testing indoors, buy an inexpensive illuminator like photographers use to simulate daylight and perform colour comparisons in front of it. If you are using a colourimeter, keep in mind, stray light may interfere with tests, so be sure to cap the sample chamber if so directed.
Myth 7: Orthotolidine (OT) solutions are more reliable than N, N-diethyl-p-phenylenediamine (DPD) reagents for testing chlorine
This myth likely started because OT solutions have a longer shelf life than liquid DPD reagents. If the pool/spa is sanitized with bromine, an OT test is fine to use; however, OT is not the best choice if the water is sanitized with any form of chlorine. This is because chlorine users must keep track of how much chemical is in its strongest germ-killing form and how much of it is past its prime. The most effective form of chlorine is referred to as free chlorine. When free chlorine has done its job eliminating ammonia and nitrogen compounds introduced to the water by bathers, chloramines (combined chlorine) are formed. Besides being a weaker, slower-acting disinfectant than free chlorine, chloramines give off a strong, unpleasant odour, which can irritate bathers, even at low levels. Together, free chlorine and combined chlorine make up the total chlorine residual.
DPD tests can distinguish between free and combined forms of chlorine. OT tests can only read total chlorine. Due to this limitation, regulatory codes governing public and semi-public facilities invariably specify operators must be able to determine the free chlorine residual, thus most codes cite DPD specifically for chlorine testing. You should make sure pool/spa owners are aware of this, as well, so they can make an informed decision about their testing supplies.
By the way, a quick way to tell if a test kit employs the DPD method is to look at the colour standards in the test block. If they are shades of pink, it is a DPD test; shades of yellow indicate an OT test.
Myth 8: A strong chlorine odour around an indoor pool, and bathers complaining of red eyes and itchy skin, indicate too much sanitizer has been applied
Similar to the answer above, combined chlorine is the real culprit here as well. To reduce these chloramines, the water actually needs to have more chlorine added—up to the so-called breakpoint level.
Generally, the formula followed for breakpoint chlorination is to raise the free chlorine level all at once to 10 times the measured combined chlorine level. If breakpoint is not achieved, the problem will become worse. Superchlorinating this way will also oxidize any organic matter, resulting in crystal-clear water. The procedure is best performed in the evening to minimize chlorine destruction by sunlight.
Myth 9: When balancing water, a total hardness reading is more desirable than a calcium hardness reading
Total hardness consists of both calcium (Ca) and magnesium (Mg) salts; however, only the calcium component is relevant in the LSI water balance calculation for pools/spas. This calculation considers the interrelationships of four chemical factors—calcium hardness; pH; total alkalinity, as corrected for the contribution of any cyanuric acid stabilizer in use; and, to a much lesser extent, the TDS level; plus one physical factor, water temperature.
Calcium hardness must be actively managed—along with pH and total alkalinity—to keep water in proper chemical balance. The only way to lower calcium hardness is by partially draining the pool/spa and replenishing with water containing lower levels of calcium hardness. Current industry standards require calcium hardness levels to be maintained in pools at the ideal range of 200 to 400 ppm, and 150 to 250 ppm in spas. Pools regularly sanitized with calcium hypochlorite (Ca[ClO]2) (cal hypo) will see the calcium hardness reading steadily increase. To avoid going out of the recommended range, at some point it will be necessary to switch to another form of chlorine for a period of time.
Myth 10: The effectiveness of a reagent primarily depends on how old it is; or manufacturers recommend replacing reagents annually because they want to make more money, not because it is the prudent thing to do; or keeping your test kit in a refrigerator between use will prolong reagent shelf life.
Misinformation about the useful life of reagents is widespread. I’ve lumped several myths together here that can all be cleared up with the simple understanding that reagents are by nature perishable, just like milk, produce or medicines. This is true whether they are liquids, powders, crystals, tablets or test strips, although shelf life does vary by type. For instance, if kept dry, powders and crystals are very stable; acids are also long lived. Other reagents are more susceptible to degradation, like DPD or silver nitrate (AgNO3) reagents. (Their opaque bottle is your hint the reagent is very light sensitive.)
Proper storage is key
Date of manufacture is not the controlling factor when it comes to shelf life—storage conditions are more important. When not in use, reagents do best in a cool, dark place, away from volatile treatment chemicals, especially chlorine and bromine. Inventory should be dated and rotated according to the first in, first out (FIFO) principle. Ideal storage temperatures are between 2 to 29 C (36 to 85 F). If you must choose between a hot warehouse (or vehicle trunk) and the refrigerator, opt for the latter for longer-term storage. Keeping reagents in the refrigerator will prolong shelf life; however, once removed, they should be used completely rather than subjecting them to constant fluctuations in temperature, which will cause them to degrade faster. Accidentally freezing a reagent may not render it useless; ask the manufacturer.
Proper handling procedures
Exposure to air and humidity is detrimental; therefore, be sure to keep containers sealed when not in use. It is also important for preventing contamination not to switch bottle caps, place bottle caps on soiled surfaces, or repour reagents into receptacles that have not been thoroughly rinsed out first. Finally, keep wet fingers away from unused strips and be sure not to accidentally touch the reagent pads during a test.
When is it time to replace reagents?
With all these environmental influences, you can see how an expiration date might give someone a false sense of security. Most reagent manufacturers recommend starting each swim season with fresh reagents; and immediately replacing a solution if it is not the colour you are used to seeing, when you see floating particles that do not dissolve when shaken, if the reagent has begun to stain its container, or if liquid has crusted around the tip of the dropper bottle. There may be no visual cue that a test strip has reached the end of its life, so definitely do not go past the use-by date.
Myth 11: When customers are educated about water chemistry beyond a certain minimal point, they will have no need for you
In our household we value the experts who keep life running smoothly, including the lawn care business who keeps our grass green and weed-free, the mechanic who keeps our cars running and the financial advisor who keeps our retirement hopes alive. Notably, each of these service providers is very good about explaining what we need to do and why, and what choices are available to us. Thus, over the years, we have gained some knowledge in all of these areas, allowing us to recognize their expertise and feel comfortable handing over responsibility to them.
Even with this knowledge, we do not have the technical aptitude or self-confidence to become independent, let alone have the time to spend doing these chores without the assistance of a professional.
This personal experience convinces me that, when it comes to water chemistry, only your educated customers will fully appreciate how you save them time and worry; how you look out for their best interests, by staying current with advances in technologies and new product offerings in order to maximize their pool/spa enjoyment; and your charges are commensurate with the value they receive. The effort you put into educating your customer will create loyalty and a willingness to recommend your business to friends and neighbours.
This article was written by Patricia Fitzgerald and originally appeared on Pool & Spa Marketing [link].