Can't maintain FC with SWG

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dougster5000

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Jan 25, 2009
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This is my first post but I have been visiting the board for a while. I just filled this pool for the first time in January. Since the pool has warmed up to above 80 degrees I have been having trouble keeping FC above 1 ppm with my SWG. I have been running the pump at least 14 hours/day with the setting on the SWG at 80 out of a possible 100. I finally decided to add liquid chlorine yesterday. I turned off the SWG and started adding 10% liquid chlorine yesterday about noon. By dark (8:30 pm) I had added 1 gallon of liquid chlorine and the FC was only 4.5 ppm. I shut everything down and tested the FC this morning and it had dropped to 2.5 ppm. It appears I just need to shock the pool, but I wanted to make sure I wasn't missing something before I took the FC to 21 ppm. My test results from yesterday before adding the liquid chlorine were:

FC: 1.0, TC: 1.5, PH: 7.4, TA: 80, CYA: 60-70, Borates: 45 ppm, CH: 350, Salt: 3300 ppm.

Thanks for your help
 
That sounds like a plan. Raise it to shock level again tonight and repeat the overnight test. If your water is clear, it shouldn't take too long shocking to correct the issue. Other than chlorine the numbers look good. If you want to tweak it, raise the CYA to 70-80.
 
Hey, Dougster,

Welcome to the forum. I don't see anything you're missing. It sure sounds like you've got some organics cooking in your pool and you need to shock to eliminate them.

I wouldn't hesiate to calculate a dosage up around 25ppm and then (here's the key to this process) hold the 25ppm there constantly by adding chlorine until your overnite FC loss stops.

We're working on an overnight FC loss article in Pool School so, if it's not clear how to do it, post back.

The shocking process will be finished when....
1. Your pool water is sparkling
2. Your CC's are .5ppm or less
3. You can hold your FC overnight without losing more than 1ppm.
 
Thanks for all the input.

I found the source of my organics. The pool builder had put a cannister type filter with a clear plastic cover on the auto water fill line. I pulled the cartridge filter out and it was covered with green algae. So I was apparently introducing algae into my pool through the auto fill line. I threw the cartridge away and filled the cannister with a mixture of bleach and water to kill all the algae. I closed the valve on the auto fill and will be replacing that section of line with 3/4" PVC this weekend, so that should eliminate the source. I have taken the covers off the lights in the pool and brushed the lights down.

The last two nights I have raised the FC level to 25 only to find it at 15 yesterday morning and at 18 this morning. It is a slow process but it seems that I am making headway. The water remains clear with no apparent signs of algae, I just keep losing FC. Hopefully one more day will do it.
 
This is a really late update, but I think it is worth posting as it may save someone some money. I finally found the real reason that I couldn't keep the FC up with my SWG. I live in west Texas where the water is really hard and has a pretty high calcium content. The SWG kept forming calcium carbonate scale on the grids where the chlorine is generated. As soon as the scale formed the FC in the pool would drop. I have since switched to bleach and or chlorine tabs. Just a tip to be sure and verify that water in the area in which you live is compatible with a chlorine generator before you spend the cash on one.
 
Dougster5000, I know this is too late for you, but most swg users, even in with high CH water should be able to control the scaling on the swg plates by keeping TA and ph a little lower. My CH out of my well runs above 300 ppm and I have not had to clean my cell the last two years.
 
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