Liquid Chlorine vs SWG CYA recommended levels

[swamprat69]

I have noticed a large difference between recommended CYA levels for liquid chlorine vs SWG pools. Living in Las Vegas with a high UV Index, I have found it difficult to maintain chlorine levels with CYA at 40-50 due to large daily swings. I seem to have found what I consider a sweet spot with my CYA at 80 where with a 2 bather load for 1 Hr./day I can maintain FC @ 9-11 by adding 1/3 gal 10% liquid chlorine and PH @ 7.6 with 1/5 gal muriatic. Am I likely to cause any problems by having CYA higher than recommend? FC 9-11, PH 7.6, TA 90, CH 750 (Very hard water in LV, Need some cool deck repairs and plan on either drain/refill or RO when deck repairs are done...Covid-19), CYA 80, Pool Temp. 86, CSI 0.36.

 

[mknauss]

No issues with the higher CYA. You must be vigilant about your FC levels, as it sounds you are. I am impressed your pool only consumes 2 ppm FC per day. Mine is near 4.5 ppm this time of year.

I have a SWCG. Makes life much easier. You might consider it.

 

[swamprat69]

Only downside that I have seen is that I need more R-0870 in order to check FC levels accurately. It seems easier to control FC with the wider band between Min-Target FC afforded by a higher CYA level.

 

[mknauss]

True -- I would suggest letting the CYA come back down starting at the end of August. It will degrade some each month. That way you are not maintaining the higher FC during the winter.

 

[conphil]

Mine is near 4.5 ppm this time of year.
I have a SWCG

To "mknauss"
You indicated that your SWCG is delivering 4.5ppm. Help me understand how you know how much chlorine your SWCG is producing. Do you just rely on what the manufacturer reports in it's specs (adjusting, of course, for your daily run-time)? Or is there something else in your measurements? (I'm trying to calculate my own chlorine useage to see how well it compares.)

 

[mknauss]

Use the Effects of Adding Chemicals in Poolmath. Select your SWCG, % generation, and pump run time. It gives you how much FC it adds to your pool each day.

 

[conphil]

Select your SWCG, % generation, and pump run time. It gives you how much FC it adds to your pool each day.

To "mknauss"
Thanks so much for your reply. I've done exactly what you stated, but I was wondering how accurate the SWCG is... for example new vs. aged unit or salt level high vs. low. Specifically, the results of this calculation suggests that my daily FC use comes out to 1.6ppm... a very low number. I was expecting a result similar to the following: several weeks ago I had completed a SLAM, and as the FC level was coming down, I continued to monitor FC day and night (like multiple OCLT's). For 3 sunny days in a row, I turned off the SWCG and lost exactly 2ppm per day (values from 14 down to 8). These numbers seem quite low compared to what you reported. Maybe I should just be content that the pool is well balanced and using less chlorine.

 

[mknauss]

Maybe I should just be content that the pool is well balanced and using less chlorine.

You live in Florida. Your UV load on your pool surface is less than ours here in the SW desert at this time of year.

I am sure the units put out slightly variable amounts. Mine has been pretty consistent since day one.