CYA Recommendation for SWG?

[tush17]

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New to pools. Converted my system to SWG with a Hayward AquaRite system. Finally got it up and running with the correct salt levels with help from this board. Wondering if I need to elevate my CYA level. I’m only at 30, which was great when I was slamming my pool. I see that some people recommend CYA of 60 for salt water, but then won’t I need way too much chlorine when shocking? Also would my base level chlorine for daily use need to be higher as well?

Bonus question : what’s the best setting for my system? Right now I’m at about 35%. T15 cell. 20,000 gallons

 

[mknauss]

You should have less FC loss on sunny days with an elevated FC. And one never needs to 'shock' a pool using TFPC protocols.

The best setting for your system is what it takes to replace the FC lost each day to the sun and organics. Start at 3 ppm FC per day and work from there.

 

[chazas]

Follow the chart. My CYA is at 60, the lower end of the SWG range, which works fine for me. You’re even further north so probably that would be ok for you too. Your SWG setting is whatever keeps your FC level always within the recommended range - people will probably do calculations for you, but I just do trial and error. Set higher at the beginning of the season and slowly lower the setting until I get where I want to be.

 

[Jimrahbe]

Bonus question : what’s the best setting for my system? Right now I’m at about 35%. T15 cell. 20,000 gallons

T,

Your cell will increase your FC by about 8 ppm, when run at 100% output and for 24 hours. That would be .33 ppm per hour.

If your pool uses 2 ppm of FC per day, you would need to run the cell for 6 hours at 100%, or 12 hours at 50%, or 17 hours at 35%, etc. This should replace the 2 ppm of chlorine that your pool lost. The higher the FC loss, the more you will have to run the cell. The higher the CYA, the less FC loss there will be.

As a side note.. I have three saltwater pools that (In total) have been TFP pools for over 25 years. In that entire time, I have never added even a single bag of pool store "Shock". If you keep your FC and CYA at the proper relationship, adding routine amounts of "shock" is just not needed. See the saltwater section of this chart. FC/CYA Levels

Thanks,

Jim R.

 

[markayash]

After battling CYA in the tablet days I was hesitant to raise it back up. But after a fresh fill my CYA was around 50 and my SWG seemed to struggle to keep FC at 5.

Bumped CYA to 80 and FC jumped to 10 with no other changes. I have since turned it down and even with 90 water temp it’s stable at 6 now

 

[iadams]

You should have less FC loss on sunny days with an elevated FC. And one never needs to 'shock' a pool using TFPC protocols.

The best setting for your system is what it takes to replace the FC lost each day to the sun and organics. Start at 3 ppm FC per day and work from there.

I don't fully disagree with the statement "And one never needs to 'shock' a pool using TFPC protocols" BUT for those of us who live in areas where we have to close the pool down for winter, and may have weather that can cause the water to warm but is too early to risk opening the pool, or can't open the pool early for other reasons (heavy pollen, leaves, weather/debris, freezing again, issues with worms, etc), it can be hard to not get some growth/biologicals and need to SLAM at the beginning of the season. "Never" seems strong here, especially when some of us do have to, and the CYA does make a difference when we do.

My winter drain-down and spring refill would not dilute the CYA down to my preferred range of 30 or less to SLAM if I had it CYA 70-80 (the recommended level) the previous year. The CYA levels recommended here for SWCG pools seems very high, and may be geared more toward Southern pools with more sun and higher sun angles and who may not close or at least have much longer seasons? It's much higher than my SWCG manufacturer recommends, and it would also mean the spring SLAM would require a much higher FC level - which I have been having a harder and harder time getting liquid chlorine every year (hence why I went to a SWCG).

I have done TFPC protocols for 10 years now, and the only time I've had to SLAM is in the spring (THANK YOU TFP!!!!), and normally my CYA levels are quite low at opening, and once the SLAM is over I raise the CYA. I plan to keep the operating CYA closer to 50-60 even with the SWCG for the above reason (and it's also within manufacturer spec). That said, I do keep a solar cover on as much as possible, mostly to prevent evaporation, so my chlorine demand increase from the sun is minimal.

The OP is in Toronto, so has a fairly short 'open' season compared to many people here, and may have many of the same issues I mentioned.

 

[Jimrahbe]

And one never needs to 'shock' a pool using TFPC protocols.

Marty was talking about routinely adding bags of pool store shock once a week, or every two weeks, like the pool stores recommend. Not whatever routine you have to go through to bring your pool back to life after being closed for the winter.

Thanks,

Jim R.

 

[gingrbredman]

And one never needs to 'shock' a pool using TFPC protocols

he only time I've had to SLAM is in the spring

Those are two different terms used, shock, and SLAM. With TFP, you would never "shock" the pool, that seems to be a term used by pool stores to over chlorinate the pool for a short period of time and move on. The SLAM is much different and methodical, which is what you would be doing based on your example in the spring. I have seen a lot of experienced pool owners need to SLAM, some for the very reasons you mentioned. But "shock" isn't something TFP uses in their methodology. I can see why you would disagree if @mknauss said you would never need to SLAM the pool, but there are situations when it is needed, and a lot of help around here when you are going through it.

Bonus question : what’s the best setting for my system? Right now I’m at about 35%. T15 cell. 20,000 gallons

I'll try to answer the bonus, but my answer is, it depends haha! You really need to experiment with the right settings. @Jimrahbe had a much better answer, but it does really depend on how long your pump runs for during the day, and then you can tweak the settings. I have an oversized cell, and find I run mine at 20% in the hot months, but usually only about 10-15% early and late in the season. That is the beauty of the great test kit as well, you can see what the output percentages do to your daily chlorine levels. When I was going through my tweaking, I went through the powder for the tests in no time because I tested frequently. Once I dialed it in, I can go a few days without testing, and even get away with a Taylor three way test to make sure everything is in balance.