Summer is the pool and spa season, so here are a few tips for you on pool and spa water chemistry:
1. Algae bloom? Check nitrate.
If an algae bloom occurs in a pool, check the nitrate level. Nitrates can get into a pool from a variety of sources, including fertilizer overspray, bird droppings, rain and well water. Unfortunately, algae love nitrates; if the nitrate level is too high, you may encounter algae blooms even though the water appears to be perfectly balanced. Keep the nitrate level below 10 parts per million (ppm); if your test strip reads above that level, you should partially drain and refill the pool.
2. Maintain a chlorine residual
Even if you’re using an ozonator or a mineral purification system, you still need to maintain a residual chlorine level. Most of the ozone in a pool will dissipate within 30 minutes. After the ozone becomes depleted, you need some residual chlorine to protect the water from any additional contaminants that may be introduced. Similarly, chlorine supplements a mineral system by oxidizing contaminants and preventing algae growth. You should maintain a minimum of 0.5 ppm free chlorine in pool water if using one of these alternate sanitizing systems.
3. Watch cyanuric acid level
Keep the cyanuric acid level in the right range to avoid chlorine loss. In outdoor pools, the sun’s ultraviolet (UV) radiation quickly breaks down chlorine. Cyanuric acid stabilizes the chlorine against effects of sunlight, acting like sunscreen for the pool. But too much cyanuric acid can reduce chlorine efficiency. It also will elevate the total dissolved solids (TDS) level, which may cause scale formation, stains or cloudy water. Use test strips frequently to keep the cyanuric acid level in the ideal range of 30-50 ppm.
4. Balance and hot tub TDS
If the water is balanced in a hot tub but you’re still having trouble, test the total dissolved solids (TDS) level. The TDS increases every time you add chemicals to the water. In hot tubs, where jets and high temperatures speed up evaporation, the TDS level builds up more rapidly. Elevated TDS can promote bacteria growth or corrosion, even when the water seems to be properly balanced. To avoid these and other problems, use a conductivity meter or TDS test strip regularly.
5. Test total, not free, bromine
In a brominated hot tub or pool, be sure you test for total bromine, not free bromine. Total bromine includes free and combined bromine (also called bromamines). Unlike chlorine, both the free and combined forms of bromine are effective sanitizers, so you need to measure them both. One word of caution—some test products measure both free chlorine and bromine. This type of test only measures free bromine, and will not give the most accurate picture of the sanitizer remaining in the water.
6. Know your sanitizer pH
Learn the pH of various sanitizers; they can help you balance the pH in the pool. For example, if you normally treat a pool with trichlor tablets (very acidic, with a pH of 2.8), then use sodium hypochlorite (pH of 13) when you shock the water. They will offset one another, helping to keep your pH in the ideal range of 7.2-7.6.
7. Know your limitations
Know the uses and limitations of your testing method. If using an OTO test kit, keep in mind that it only tests for total chlorine, whereas free chlorine is the effective sanitizer in a pool. DPD kits measure free chlorine; however, they’ll yield false positive readings for free chlorine in the presence of very high combined chlorine (chloramines) levels. This is a frequent problem when opening pools in the springtime. Finally, all liquid reagents and test strips will expire. For accurate results, use a test product with a clearly marked expiration date, and don’t use the kit or test strips beyond that date.
8. It’s OK to be shallow
You don’t have to dip your test strip 18 inches below the surface to get accurate test results. With any circulation at all, the chemical levels at the surface will be nearly identical to the levels at the bottom of the pool. The difference between 2 inches and 18 inches below the surface would be even less significant. Therefore, testing at fingertip depth is all that’s required.
9. Spring is more demanding
Chlorine demand is often significantly higher in the spring when opening pools. When a pool is closed, microorganisms that aren’t destroyed by chlorine, or some other sanitizer, will grow and multiply in the water. This is common when a pool is opened for the first time and there’s no free chlorine present. Under these conditions, you may need to add as much as 200 ppm of chlorine to re-establish a free chlorine residual.
10. Follow the directions
Whatever type of testing product you use be sure to follow the manufac-turer’s directions. Most inaccurate test results occur when individuals don’t follow directions—or follow the wrong directions. Not all manufacturers’ test strips are the same; updated versions of products may also use different test procedures. Therefore, you should never assume that the directions on one container are going to apply to another container’s strips.
About the authors
Joe Sweazy is a technical service associate for Environmental Test Systems, manufacturer of water quality and pool and spa test strips, based in Elkhart, Ind. He has published more than a dozen articles on pool and spa water chemistry and has presented numerous seminars at conferences of the National Spa and Pool Institute. Sweazy earned a bachelor’s degree in chemistry from Bethel College in Mishawaka, Ind., and is a Certified Pool and Spa Operator (CPO). He can be reached at (800) 548-4381, ext. 179, or email: email@example.com
Drew Chuppe is the senior marketing manger for AquaChek™ Pool & Spa Test Strips at Environmental Test Systems. He and Joe Sweazy are co-authors of the AquaChek™ Dealer Training Program—a free, Internet-based training course on pool and spa water chemistry at www.aquachek.com/training. Chuppe can be contacted by email: firstname.lastname@example.org