We visited a pool earlier this week because the salt light had just started blinking that the pool needed more salt. While our service team was on site, we noticed that the pool had a thin film of green algae on the bottom of the pool, as well as a few more stubborn spots. After adding a bag of salt to the pool to make sure the ppm concentration of the salt was adequate, the pool was brushed down to remove the algae from the surface of the vinyl liner, and allow the algae to circulate in the water to allow the chlorine to do what it needed to and kill the algae.
What caused this condition in a pool that is supposed to be almost maintenance free? Why did it allow algae to form? In this case, the pool and spa are operated with an IntelliTouch system by Pentair. The weather has also been hitting 100 degrees for several weeks.
When we checked the programs in the control panel we found a few programs that were running the equipment. The spa was set to come on 4x/day for between 15 and 30 minutes at a time. This was good, it allows the spa to run and chlorinate itself, since it is not a spillover spa situation and the two bodies of water function separately. The other program that we found for the pool however, made our algae possible. The pool was set to run from 8am to 11pm, minus the time that the spa was set to run. Since chlorination, or the chlorine generating only happens while the pool is running, we were chlorinating at the most for 15 hours/day. The Pentair IntelliChlor systems come in several models. For most residential installations it’s either the ic20 (for 20,000 gallon pools) or the ic40 (for 40,000 gallon pools). For the unit to produce it’s maximum level of chlorine, it needs to run for 24 hours to produce the appropriate level. So if an ic20 is only set to run for 15 out of 24 hours, it’s not able to produce enough chlorine for the pool. In this case, the generator was running and generating chlorine only when the pool system was running. By changing the programming schedule to run continually for 24 hours a day, and allowing the spa to continue to function for several hours a day we were able to correct the issue and allow the pool to produce the appropriate amount of chlorine for the conditions.
A couple of other things could also help in this situation. It would be okay to add a case of liquid chlorine to boost the chlorine levels in the pool, and hold off or control the algae situation. It would also be advisable to add an algaecide to help remediate the problem. One final level to check would be the conditioner or stabilizer level in the pool. Sunlight is one of the main reasons that chlorine leaves a pool, or is “burnt off”, reducing the levels by as much as 1ppm / hour on sunny days. Adding stabilizer and making sure the levels are in the mid-range will help keep a clear, swimmable summer pool!
If you have any questions about whether an IntelliChlor system would be right for your pool, or any related water chemistry questions, just Ask the Pool Guy. We are here to help!
