Will "Shocking" The Pool Have A Bearing On The Backwash Schedule?
by J.D. Ventress
Friday afternoon the ARV indicator needle was showing 11. I "shocked" the pool Friday night and Saturday morning the needle was showing 18 (20 would indicate a backwash needed). I noticed this same thing last week and a few days later needed to backwash the filter as the ARV read 20. I used a one pound bag Sodium Dichloro "shock" (Aqua Chem Brand) and boosted it with one 4oz cup of granulate multi-function chlorine. I've been experiencing difficult in getting the CL to the proper level. Appreciate your advice. J.D. Ventress Thanks for the question J.D. Being that the question doesn't say whether you have a sand or DE filter, it would be difficult to give a concise answer without going through the troubleshooting of both kinds of filters. If you could give your kind of filter it would help. Sand and DE filters have different issues. Be sure the gauge is working properly. An easy way to do this is to turn the system off. If the needle drops to zero, you're fine. If not or if the needle sticks, replace it. I'm not aware that shocking a pool will require back washing because the pressure rises. If your pool is clean and clear, free of algae, then there shouldn't be a rise in pressure. Concerning your shock, you're using Dichlor for every shock. This has a stabilizer in it, cyanuric acid, or CYA. If you shock with this on a regular basis your CYA will go through the roof. You want to keep the CYA between 30 - 50ppm. For every 10ppm of chlorine added with Dichlor, you'll increase the CYA by 9ppm. I would encourage you to test for the CYA is see where it is. The kit I use and recommend is a Taylor FAS-DPD K-2006 pool test kit. Pool Water Testing Water Testing Kit If it's high the only way to reduce it is to drain 1/3 - 1/2 of the water, refill, and balance out the chemicals. It would be good to have your chemical readings as well. If you keep your chlorine between 1.5 - 3.5ppm and CYA between 30 - 50ppm, there's really no reason to shock every week. If you're shocking to get rid of the organic matter and bacteria, that's what the chlorine is for. When I had my pool route in Arizona I never did a regular shock to my customer's pools. It didn't need to because I kept the levels where they were supposed to be. Only if you have a heavy bather load on a consistent basis or are expecting one should you shock (algae is the exception). And this should be after testing for chloramines, or combined chlorine, either with a DPD kit or your local pool store. If the chloramines are above 0.6ppm for three consecutive days should you shock. This is when I shocked the YMCA pool. You can find your post in the "Shocking A Pool" category on the Q&A page: Swimming Pool Questions and Answers Give me your chemical readings and kind of filter and check back to this post for your answers. Hope this helps and I look forward to hearing from you. Robert
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