This problem plagued me for 4 weeks until I finally found a knowledgeble person to help me. Use this technique and you can clean a heviliy algead pool in 3 days. 1st get your water chemistry balanced with a high PH and nominal chlorine level 2nd. turn off your filter. 3rd. Add Aluminum sulfide (alum) to your pool. This is a coagulant that can be purchsed at better pool supply stores. IMPORTANT: do not run the filter! 4th. wait at least 6 hours with the filiter off. 5th. add water to pool positioning the hose end in the skimmer recess and raise the level to the top of the skimmer port. Your water should now be clear, but you have a lot of dead algae on the botoom of your pool. Don't be mislead into thinking your pool filter will clean it out -it will not. This junk must be vacuumed to waste. 6th. Plug the vacuum hose into the skimmer port (keep the filling hose tucked into the skimmer port next to the vacuum hose). 7th. set your filter to waste and begin vacuuming. Make an effort not to stir up the debris as you vacuum, this is hard but with practice you will get the hang of it. 8th. Vaccum as long as you can still see what you are doing (with severe silting it is inevitable that you will stir up dead algae and no longer see the pool bottom). Because your garden hose is tucked next to the vacuum port you should be able to vacuum until the water level is no more than 18 inches below the skimmer port. 9th. stop vacuuming and turn the filter off. It is o.k. if your water looks green again because of the stirred up algae. Leave the filter off!!! also leave the vacuum and garden hose in place and bring the water level back up. 10th. repeat the vacuum and fill process 3-4 times or as needed. you can add chlorine during this process, but do not run the filter as it will only stir up the water again. Use a brush to get isolated pockets of debris as needed. 11th. When the debris is off the pool bottom AND your water is clear you are now ready to shock and add PH increase to your pool and begin operating your filter at normal intervals. This technique requires a good deal of new water and vacuum time, but it works great. I can't stress enouph about avoiding any method that involves the filter to clean dead algae. The dead algae particles are just too small to be trapped in the filter, be it DE or sand.
New answer:
My goodness, why go to all those steps and waste all that water and man hours. Above not the best method - totally obsolete. You did not say how large the pool was or if it was a plaster pool finish. If plaster, first back wash the filter, sand or D.E.
1. Add three to four gallon of 12% liquid chlorine, 10% if you can't find the 12.
2. Extend the filter/pump run time to 24hrs. Remove the time clock trippers for this if you have one.
3. Brush the pool walls and floor at least twice per day during the process then as needed - with a nylon pool wall brush.
4. Next day check for water clarity. The water should look markedly better. Back wash filter again and if needed adjust water level. Test for chlor. level and keep at or above 5.0 or 3.0 if your test kit doesn't go that high. Also then, adjust your pH. If your water has cleared greatly then adjust your time to about 15-18 hrs. until water is crystal clear. You may have to back wash again at the end of that time or before. The chlor. will kill the algae and the filter will pick most of it up through circulation and you most likely will not have to use any toxic chemicals. With a sand filter this process may take longer because the sand in the filter cannot filter fine enough.
5. Once you have achieved your goal you may then cut back the run time to about 12 - 15 hrs. depending upon gallons of h2o involved, pump and filter sizes. The probable cause of original problem was not enough filter run time and no free chlorine levels. It just got ahead of you and it could happen to a pro because of the heat and humidity.
6. If you still have a chlorine level above 5.0 wait a day to use the pool. Oh, and you might want to check and adjust your conditioner/chlor. stabilizer upward if needed. Should be about (for me) 50 to 80 ppm.
Happy swimming.
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