SWG vs Bleach levels

[yoster]

After 1 year of using the TFP method (which worked very well btw, although, quite expensive these days) - I've decided to move to a SWG.

Looking at the TFP CYA/chlorine charts - I was surprised to see that 'minimum' and 'target' levels of chlorine are lower for a SWG pool (vs bleach) for every given CYA level. Can someone explain why that is? What about going SWG makes it so that min and target chlorine levels would be lower? Does it have to with the fact that water is going through a chlorinator unit (more "saturation" for every given PPM of chlorine?)

 

[mknauss]

Has to do with the consistent addition of chlorine. In the Deep End it is explained from anecdotal evidence.

 

[Newdude]

see that 'minimum' and 'target' levels of chlorine are lower for a SWG pool (vs bleach) for every given CYA level. Can someone explain why that is?

Said chart was designed when folks had 'properly sized' units that needed to be run all day. It was like standing there and matching the UV loss, drop for drop, instead of dumping a gallon of bleach in to spike it and drifting down over the next 24 hours. So with very little fluctuation, lower FC levels were sustainable while remaining above minimum for SWGs.

Nowadays, folks are buying 3X, 4X or even larger units which only need a couple hours of runtime to produce the same FC. Or others are only running theirs at night for electric bill savings / off peak. These pools should follow the LC side of the chart because they will not be producing FC during the day and their pool will swing closer to a LC pool.

If you're producing FC during the peak time of the day, you can use the lower FC values, but I always rec having some safety net. We call it running 'hot' and it will be a huge help to you as you learn a new system. It works so well, I never gave up the safety net once I learned.

 

[yoster]

Thanks. Any chance of the Pool Math app being updated then? That info you just provided is relevant and probably relates to the vast majority of users. Poolmath recommendations (which mimic the chart) are misleading in this case.

 

[mknauss]

Poolmath follows the TFP recommended levels. You are welcome to change the Goal as you like.

 

[Jimrahbe]

yoster,

When you switch over to a SWCG, I suggest that you just try to keep your FC at your 'target' or higher. I do not recommend trying to keep your FC between your 'target' and your 'minimum'.

Trying to keep your FC between the target and minimum will just work you to death. You will have to constantly micromanage your SWCG's output, and you will be changing it every few days.

If you just worry about going too low, it is an almost hands off situation. Running a little higher than the target has no downsides.

Thanks,

Jim R.

 

[yoster]

Poolmath follows the TFP recommended levels. You are welcome to change the Goal as you like.

That's my point - TFP recommended levels are inconsistent with what Newdude just described. From his description, it sounds like they're outdated/lower than what they should be today.

The Free Chlorine and Cyanuric Acid Relationship

Managing your cyanuric acid and Free Chlorine levels is key to stabilizing your pool. Learn how these two items affect each other.

www.troublefreepool.com

Example. Lets use 70 CYA as a baseline. Liquid chlorine shows 8-10 Target FC. SWG shows 5. That's a dramatic difference. According to newdude, it sounds like that's inaccurate? I should follow the liquid chlorine figure??

yoster,

When you switch over to a SWCG, I suggest that you just try to keep your FC at your 'target' or higher. I do not recommend trying to keep your FC between your 'target' and your 'minimum'.

Trying to keep your FC between the target and minimum will just work you to death. You will have to constantly micromanage your SWCG's output, and you will be changing it every few days.

If you just worry about going too low, it is an almost hands off situation. Running a little higher than the target has no downsides.

Thanks,

Jim R.

Not keeping them that low - just using it as a point of comparison.

 

[mknauss]

That's my point - TFP recommended levels are inconsistent with what you just described. From your description, it sounds like they're outdated/lower than what they should be today.

Just because some members wish to run a higher FC, fully their prerogative, the TFP recommended levels will work just fine.

 

[yoster]

Thx - that makes sense. Also, edited my last response. Apologizes - said "you" when I meant newdude! Getting people confused over here LOL

 

[ajw22]

Example. Lets use 70 CYA as a baseline. Liquid chlorine shows 8-10 Target FC. SWG shows 5. That's a dramatic difference. According to newdude, it sounds like that's inaccurate? I should follow the liquid chlorine figure??

Dramatic difference, nah.

At CYA 70 you can run a FC level up to 28.

So your safe FC range is between 5 and 28, a 23 ppm range.

Running your FC between 5 and 10 is running in the lower third of the safe FC range.

You have plenty of headroom to have your FC drift above 10 due to inattention and be safe.

There are dragons that lurk when your FC drops much below 5.

So as @Newdude pointed out it is less work and worry to run at 8-10 then try and skirt above 5.

 

[Newdude]

That's my point - TFP recommended levels are inconsistent with what Newdude just described. From his description, it sounds like they're outdated/lower than what they should be today.

We aim to teach people how to manage their pools on the fly. The environment and your equipment can change, and so will your pools needs/abilities. For example, if you clear lots of foliage, you may suddenly have less organic matter blowing in the pool, needing less chlorine to keep it sanitary. Or clearing said foliage greaty increases the sun hitting the pool, increasing your daily demand. Or you oversize your SWG which can achieve same production in much less time.

If you know what your pool needs and how to manage it, you can slightly adapt the one size fits all reccomendations to how they fit best for you. People tend to see the FC chart and PoolMath as absolutes when in reality they are starting points which require you to reasses as things change.

 

[Newdude]

I'd also like to point out that the same general wisdom that at times makes things look inconsistent, is our greatest strength here.

For example, calcium levels for plaster pools. We have found through road testing the reccomendations hundreds of thousands of times that those with high Calcium fill water don't need to immediately raise their CH to meet the charts. It will rise quickly on its own, prolonging the need to drain to reset it.

By teaching folks what the levels mean for them in their specific circumstances, they become full blown masters of their pool.

 

[Lake Placid]

Can someone explain why that is? What about going SWG makes it so that min and target chlorine levels would be lower? Does it have to with the fact that water is going through a chlorinator unit (more "saturation" for every given PPM of chlorine?)

In addition to the deeper dive that’s been provided here with various theoretical variables as to why you’d need to run differing FC levels, see post 1 footnote 3. Chemgeek himself stated why he set the percentages differently in the chart.

Chlorine/CYA Chart

EDIT: You will find a simplified and standardized version of this chart at Pool School, Chlorine / CYA Chart. Chlorine/CYA Chart by Chemgeek FC = Free Chlorine in parts-per-million (ppm) CYA = Cyanuric Acid in parts-per-million (ppm) CYA ........... Min FC3 ..... Target FC ...... Yel/Mstrd...

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