CYA levels with a SWG

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sredish

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Jul 3, 2007
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North of Dallas
I've been having a problem with getting the FC levels maintained in my new pool. I've been working on getting the PH down and finally have it in the close region, around 7.6 from what I can tell on this guess strip. I've been supplementing with bleach some to maintain the levels.

The guy who installed the SWG said that with running one of these units, you have to maintain higher CYA levels to compensate for the slow disbursement of chlorine. He said I need to have it in the 70 to 80 range for the SWG to be able to maintain it efficiently. Based on the Chart here on the site, it said min. FC would need to be around 5ppm.

Seeing as it's an SWG unit, do you guys feel this is a good recommendation? Do you guys feel that 70 to 80 is a proper level for the SWG units? I was going to try and maintain 3 to 4 ppm in the pool. These strips are very vague. In regards to the CYA, it has a 0 mark, a 30 to 50 mark, then a 100 mark and so on, not even counting the inaccuracy percentage. To actually get 70 or 80 will be hard with this deal. I have a LaMotte ColorQ on order, shipping tomorrow but I'm trying to get by.

I have what seems to be in the 20 / 30 range... hard to tell, so I figured I'd start with trying to raise it 30ppm, using the instructions on the back to do it.

Later.
 
First, get a real test kit. That is the best investment in your pool you can possibly make. Test strips seem to be particuarly bad at measuring CYA.

Higher CYA levels often work well with a SWG. The higher CYA keeps the chlorine from getting burned off by the sun as quickly so the cell doesn't need to run as long. Many people have also found that you don't need to maintain as high a FC level with a SWG as you do with bleach, though why this works and just how effective it is is still debated.
 
sredish, I have the Aqua logic 8 zone controller with Aqua Rite salt chlorine generator and am keeping CYA around 50. It was up tp 75 but after all the rains we have had much of the pool water went out the overflow pipe and into the French drain. Seems to be keeping up with FC at 3 - 4ppm. It's a smaller pool so that may be the reason. Plus, since we haven't had that many days yet with full sun I really don't know if it will maintain those levels. Will have to experiment based on conditions. May have to increase run time and increase cell production past 50%. Time will tell!
 
Experience from most SWG users is that a lower FC level than the Min column in Ben's chart still seems to work, but not for everyone. 3-4 ppm FC at 80 ppm CYA should be OK and most users can run at 3 ppm FC at 60-80 ppm CYA with an SWG, but not everyone. Some reported needing higher levels closer to Ben's Min level (and some with yellow/mustard algae needed a little more than that). It seems that a minimum FC of 4% of the CYA level works for most people, but at lower CYA you still need enough FC as a buffer for local usage so a 3 ppm FC minimum is a decent number to use.

Remember that though free-floating green algae may get super-chlorinated in the salt cell, any algae stuck in biofilms on pool surfaces is only getting exposed to the general FC level in the water.
 
Sredish, just a couple of quick comments -

If you can't wait until you get a decent test kit - tie the cya to the salt (my formula is to add 1 lb cya per 100 lbs of salt to get to 30 - 40 ppm cya @ ~3000 ppm salt)
Keep notes on what chems you add and the resulting change - once you 'get to know' how the pool will react, you'll be ready to act decisively :wink:
 
great advice guys... thanks a million.

i added 8 lbs to the pool last night. not sure how much i'm supposed to add or not add at a time but i just said heck with it. I'll let it go a week and see where it goes. My CYA was in the 20 / 30 range and according to the Pool Calc, that'll raise it 30 points. I'll leave it at that for now. My PH is holding decent right now it has about 3ppm of chlorine.

It rained like heck yesterday morning, again in the evening to the point of flooding N. Texas and it's raining right now again. So, with weather like this, it's hard to keep anything together.

Any of you see the Gainesville, TX floods on TV a couple weeks ago, well I'm about 8 miles east of there, right in the line of fire. We're just getting crazy rain here. As it sits, I have to drain about 5 inches just from yesterdays rain but since it's raining again, I might as well wait first.
 
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