Covered in scale
In one particular case, for example, a commercial aquatic facility was using a phosphate-based chemical on a weekly basis. The swimming pool was heated and also had high levels of calcium. As a result, the facility went through several heat exchangers in a short timeframe. When inspected, the heat exchangers were covered with a white ‘scale-like’ material. After laboratory testing, it was determined to be calcium phosphate scale. Having this knowledge, the aquatic facility conducted a phosphate removal treatment procedure and the phosphate-based chemical was switched to a non-phosphate product. Since switching, the facility has operated for several years without any further heat exchanger problems.
Research continues
Presently, there is ongoing research into calcium phosphate scale and fieldwork confirmations and different problems and resolutions are being accumulated.
Due to the complexity of phosphate chemistry it is not easy to predict a threshold level of phosphate scaling. To minimize risk, it is important to reduce not only orthophosphate, but also the calcium concentration. Regular draining and dilution can also help. Keeping the pH at the lower end of the acceptable range (7.2 to 7.4) is another method which can help reduce scale formation.
| Recommended Water Parameter Levels |
|---|
| • Phosphates 200 parts per billion (ppb) or below • Calcium hardness 150 to 300 parts per million (ppm) |
So, while research continues, it does appear for now that regular testing of phosphate levels and calcium hardness, along with phosphate removal treatments, can help extend the life of heat exchangers in high calcium swimming pools and hot tubs.
Terry Arko has more than 30 years’ experience in the swimming pool and hot tub industry, working in service, repair, retail sales, chemical manufacturing, customer service, sales and product development. He is also a Certified Pool Operator (CPO) and CPO Instructor through the National Swimming Pool Foundation (NSPF). Arko is currently product specialist for SeaKlear Pool and Spa Products a subsidiary of Halosource Inc., a clean water technology company based in Bothell, Wash. He can be reached via e-mail at tarko@seaklear.com.
