When I was gone over the summer the person who maintained the pool had green algae build up in the pool that is normally chlorinated with a SWG. He put powdered chlorine to shock the pool and get rid of the algae. This seemed to work but he did say that the pool appeared cloudy after he back washed the sand filter.
Now about three weeks later the pool seems to be getting just a little green and we had some winds that caused more sand to blow into the pool. So, first I also put in powdered chlorine to shock the pool. Then two days later I used a normal hose and vacuum attached to the skimmer suction (instead of my Kreepy Krauly which does a so-so job) and got the pool looking really good. Since I knew I had vacuumed up a lot of sand I then back washed the sand filter for 5 to 10 minutes until after I was not seeing anything in the visible glass and then ran it on rinse for about 30 to 45 seconds. Within about 15 minutes the pool was much greener than ever.
To complicate things I live directly on the Sea of Cortez which is 4 times saltier than the normal ocean. Rain in the desert is almost non-existent and vegetation is very minimal. Thus, the pool only gets very fine sand blowing in and only rarely a few grass clipping and/or flowers. However, the sun is very intense and the temperature is 90 during the day and 80 at night so the pool temperature is currently about 90 degrees F.
Also to complicate things I discovered that my R13 for testing CYA was used up over the summer so I will try to go to a friends today to hopefully get it tested. When tested in July the CYA was 65. Other readings are:
FC 2 I try to keep it about this for the SWG
PH 7.2 I try to keep it low because of the extremely high calcium
CH 600 Yes, extremely high but so is the water from the tap. I had looked into means of trying to lower the CH but have not found anything. The companies who do this in AZ are not interested in coming down to San Carlos even though I think it would be a good business opportunity for them.
Because of the high CH I typically have to clean the scale buildup on the Pentair IC40 SWG about every 3 weeks. This is a real pain since it typically takes many acid washes and hours to do. This is probably why the algae reappeared.
Now, I am out of powdered chlorine so last night I purchased some Chlorox to cure the algae. I tried to purchase more chlorine locally but the pool store ?? did not have any. Basically, the nearest pool store is 300 miles away in Tucson.
I am thinking that I should add the chlorox directly into the skimmer with only the skimmer valve open and give the sand filter a good sanitation this way. The chlorox obviously would then go directly into the pool and kill the algae. When the water is again clear I would think that again I would need to back wash the sand filter. Does this make sense or is there something else I am missing.
I am also thinking that a robotic cleaner makes sense because then the dirt is going into its bag and not the sand filter. Besides, the Kreepy Krauly takes at least 4 hours and still misses areas, does not do the ledge to sit on or the infinity pool, and frequently gets stuck on the stairs.