Can there be too much CYA?
Manufacturers and standards organizations have set the reference level of too much CYA at 100 ppm. This is a good rule of thumb, as it helps keep information uniform between service staff and sets a residual for pools which may have a history with water quality or algae growth issues. However, the decision to maintain higher CYA levels ultimately comes back to the pool owner.
To determine the severity of elevated CYA in a particular pool, it is important for the service professional to discuss the matter with the owner and decide whether to take immediate or future action. The main concern is the conditions in which chlorine may be consumed in the water. How often the pool is used is a key piece of information, as more pool use equals more chlorine use. One should also assess the area around the pool and the property, to find out if it is prone to windy conditions or has significant (or limited) outside plant life.
Pools with continuous circulation systems could also have CYA levels above 100 ppm. In these situations, if they are limited in one element and especially in all elements, then higher CYA levels could have limited impact on water quality or safety. However, the owner will need to be advised that if any of these conditions change, the water’s ability to correct any upsets may pose a challenge.
Pool water should always be safe water. As long as a free chlorine residual can be maintained above one ppm, CYA does not greatly hinder HOCl’s ability to inactivate or kill common germs and bacteria. The rate of sanitation and inactivation will decline, but if there is still free chlorine present, there is still the potential to help keep the water safe.
Unfortunately, the elevated presence of CYA does reduce the oxidizing ability of chlorine. Once CYA is added to the water, the millivolt (mV) levels immediately start to decline, reducing the chlorine’s efficacy in disinfecting the pool. For instance, 75 ppm of CYA can lower its oxidation reduction potential (ORP) to around 185 mV. Fortunately, if CYA levels continue to increase, especially over the 100-ppm threshold, the rate at which the ORP declines levels off. Since less germs and bacteria would be removed in the presence of elevated CYA, more chlorine (or another oxidizer) would need to be added more frequently, to reduce waste buildup and prevent common water issues.
In the presence of elevated CYA levels, there are several options which can aid in keeping water clean and clear. Simply raising the chlorine level is one solution. Maintaining a free chlorine level of 7.5 per cent of the total CYA levels is a popular methodology. Another option would be to use alternative oxidizers, such as potassium monopersulfate, to address water contamination. These oxidizers do not bond with CYA like HOCl does, so the ORP would not decrease.
The water can also be treated with additives which do not include oxidizers. Enzymes offer optimal maintenance relief, as they help break down complicated molecular structures which may otherwise prevent chlorine from effectively doing its job. Borate products can help with water clarity, algae suppression, and sustained water balance. Maintaining reduced phosphate levels can offer relief in the case of reduced chlorine levels. Keeping filters free from grease and oily deposits with dedicated cleaning solutions can also help reduce reliance on chlorine. Lastly, algaecides can help reduce algae presence.
How can CYA levels be reduced?
Currently, there are not many options available to reliably reduce CYA. Chemical treatments do exist, but strict adherence to the directions may pose challenges to the applicator. Using a portable reverse osmosis system (OS) works but requires several days and these treatment systems are not widely available. A popular service trick, which is said to reduce CYA more reliably, is to let the water settle for several days. Then, it must be vacated from the bottom of the pool using a submersible pump. Aluminum sulfate may also help reduce CYA. Regardless of how the water is removed, it will need to be replaced with fresh water to properly correct the issue.
Author
Kevin Vlietstra is the technical director and regulatory specialist with Haviland Pool and Spa Products. He has been working in the recreational water industry for more than 20 years. Vlietstra can be reached via email at kevinv@havilandusa.com.
