Trouble with SWG Math

Jump to latest Follow Reply
R

run53

LifeTime Supporter
May 4, 2010
410
Having a hard time figuring this out........

My SWG claims a production rate of 1.38 lbs. per day. ( I assume this means when the dial is set to 100%)

I've had good success running my pump 10 hours per day with the SWG set at 50%. So I did some math.......

1.38 lbs./day = 22 oz./day of chlorine gas (this is the term used in the PoolMath calculator)

So, according to PoolMath, 22 oz. Chlorine gas/day should raise FC by 7ppm each day if I run the unit at 100%

Now, back to what I actually do....run 10 hours at 50% output.

10 hours @ 100% should produce about 9.2 oz of chlorine gas
Therefor 10 hours @ 50% should produce 4.6 oz of chlorine gas

According to PoolMath, 4.6 oz of chlorine gas should raise the FC by a little less than 1.5ppm.

However, I'm pretty sure I have more than 1.5 FC loss each day as I measured it (without the SWG turned on) to be closer to 2.5 - 3.0 FC loss per day. But the 50% setting seems to be maintaining my FC at around 7.0ppm over the last several days.

Can anyone point out where my math or any assumptions I use are incorrect?
 
Hi Run!
Re:
However, I'm pretty sure I have more than 1.5 FC loss each day as I measured it (without the SWG turned on) to be closer to 2.5 - 3.0 FC loss per day. But the 50% setting seems to be maintaining my FC at around 7.0ppm over the last several days.
Click to expand...

You're using the same math I've been using to dial in/ down my new swg and you're experiencing similar results.

I seem to only be "using" about 1.5 ppm per day whereas before swg I was def more like an average of 2.5 with many days closer to 3.

I was debating earlier today to myself that this either meant my math was bad, OR maybe the beauty of constant chlorination is that with the higher cya and lower "dose" levels, much less chlorine is "wasted" via UV exhaustion.

I'm hopeful the latter is true...and it makes sense to me.
 
Daily FC loss rate can look a lot like the stock market Dow Jones data - one day it's up, one day it's down then back up again, etc, etc. it's the trends and averages that are important. Bather load, temperature and sunlight all have a part to play. In a clean, unused pool with high CYA and the standard TFP recommended levels for an SWG, FC loss can be as low as 1ppm/day. Throw in some wind-blown foreign matter and a few kids and that loss will increase.

Also, as Swampwomam points out, the consistent dosing of FC and oxidation caused by an SWG cell tends to show lower daily FC loss than the fluctuating chlorine levels found in a manually dosed pool.
 
It is true that the higher the chlorine level the faster the rate of decay. One of the reasons why we don't recommend going over shock level during a SLAM. Was your CYA at the same level for the 2.5 ppm use vs the 1.5 ppm rate?
 
pooldv said:
It is true that the higher the chlorine level the faster the rate of decay. One of the reasons why we don't recommend going over shock level during a SLAM. Was your CYA at the same level for the 2.5 ppm use vs the 1.5 ppm rate?
Click to expand...

Yes.....CYA has been 45 throughout. When I opened, I slammed so kept the CYA where it was from over the winter. Now that I've passed all 3 SLAM tests (my annual opening ritual) I will start to bump CYA to about 70-80.
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply