Quote Originally Posted by PatL34
With the SWCG on, it is better not to cover the are of the return jets, so as to allow the hydrogen generated by the cell to dissipate. The CYA at 70 ppm should be enough to keep chlorine without the pool cover.
Pat
With an FC of 3.5, going from a CYA of 30 to a CYA of 70 only increases the half-life of chlorine (in full sun) from 6 hours to a little over 7 hours. You can see from this graph that the bulk of the benefit of protection from CYA comes at relatively low levels of even 20 ppm. Using a pool cover over part of the pool will definitely help preserve the chlorine during the day.

The key is to see if the chlorine level drops significantly overnight. If it does, then algae is still being killed. If the chlorine level holds (or drops slightly), then the shocking program is near completion. I suspect that even higher levels of chlorine above 20 ppm may be required to quickly kill the algae. As for damaging the vinyl liner, I doubt that even these levels will harm it since it is equivalent in oxidation and disinfection capability to only 0.35 ppm FC with no CYA.

Richard