Trying to dial in an SWG

[talsayon]

I'm in process of trying to dial in a newly installed SWG (Circupool RJ+ 60). I wanted to test FC over a 24 hour period to see if I was getting any loss running the SWG at 100% for 10 hours. I tested after sunset 2 nights ago and got an FC of 5.5 and last night I tested at an FC level of 5 for a total loss of 0.5. I've listed my pool at 35k gallons but it could be closer to 40k (I'm not the original owner and its not an easy shape to get a perfect measurement from, when I took rough measurements today I got closer to 39k). My CYA is 70, TA 70, PH 7.5, CH 375, and salt is about 3400. That means I probably need to bump it to about 11 or 12 hour runtime. The pool does get pretty much direct sunlight from 6am to 8pm and the water temps are already in mid 80's.

Given all this, does that seem like an excessive amount of FC loss on a daily basis? Based on pool math that would mean I'm losing roughly 4 to 4.4 FC a day. Seems pretty high relative to what I've seen posted. I did an ONCT and passed a week ago but I plan on doing another this evening just to rule that out. I guess its also possible my SWG is not actually performing at the 3.1lb/day it says it should be.

 

[mknauss]

4 ppm FC loss at this time of year is not excessive.

We do know the Circupool SWCG's tend to sometimes be a bit overstated in their actual chlorine creation rate. So take that number with a grain of salt, so to speak.

 

[talsayon]

4 ppm FC loss at this time of year is not excessive.

We do know the Circupool SWCG's tend to sometimes be a bit overstated in their actual chlorine creation rate. So take that number with a grain of salt, so to speak.

I see what you did there . Good to know that its not crazy out of line. I'll do an overnight test with the SWG off and see what I get again, just to rule that out. Then I'll do another test tomorrow overnight with the SWG running to see what its actually producing all things equal, and report back.

 

[jmastron]

If interested in dialing in with data, I'd suggest this sequence. I like to do 25ml FC tests for these for better precision (otherwise I do 10ml tests):

1) Overnight loss test (OCLT) with SWCG off, just to baseline that there is no hidden algea etc using up FC, making the next tests valid.

2) Overnight gain test with SWCG on 100%. This will tell you how much your SWCG generates per hour or day, which as mentioned may or may not match "aspirational" marketing claims.

3) Daytime pool loss/usage test -- start with enough FC buffer that you can leave the SWCG off all day, sunrise to sunset. If your weather varies significantly, could be interesting to do this on a cloudy and sunny day, and in my case with the solar cover on and off (since I leave it on many days due to lack of use).

You should be able to match up #2 and #3 to dial it in the hours and % you need to closely match the FC usage with generation. Your usage level will vary greatly with CYA level, temperature, and sun (and maybe bather load and cleanliness )

 

[talsayon]

Good advice. I passed the over night chlorine test again with flying colors so no issue there. I'll do the SWG test tonight. Any recommendation on how long I need to run it for? I shouldn't need to run it all night like the ONCT I assume? 2 hours good enough? With the 25ml test what do you multiply by?

 

[talsayon]

I ran the SWG only overnight for 7 hours and only went from 6 to 7.5 in FC. Even giving it the benefit of the doubt and calling that 2 would be pretty low relative to expectations, but that would at least get me comfortable that my daily FC loss is considerably lower than what I had previously been thinking (probably closer to 2.5 to 3). Pool math says I should have seen a 2.7 to 3.1 FC increase (35-40k pool volume). Does anyone think that performance is low enough that the equipment is functioning properly, or is that really how much of a difference between "marketed" rates and real-world rates I should expect?

 

[jmastron]

Good advice. I passed the over night chlorine test again with flying colors so no issue there. I'll do the SWG test tonight. Any recommendation on how long I need to run it for? I shouldn't need to run it all night like the ONCT I assume? 2 hours good enough? With the 25ml test what do you multiply by?

The longer you run, the more accurate the data (as long as the sun isn't on the pool of course!). You'll "normalize" for the runtime anyway. Similarly, the 25ml sample gives better data -- +/- 0.2ppm instead of +/- 0.5ppm. You multiple the number of drops by 5 (vs 2 with the 10ml sample).

I ran the SWG only overnight for 7 hours and only went from 6 to 7.5 in FC. Even giving it the benefit of the doubt and calling that 2 would be pretty low relative to expectations, but that would at least get me comfortable that my daily FC loss is considerably lower than what I had previously been thinking (probably closer to 2.5 to 3). Pool math says I should have seen a 2.7 to 3.1 FC increase (35-40k pool volume). Does anyone think that performance is low enough that the equipment is functioning properly, or is that really how much of a difference between "marketed" rates and real-world rates I should expect?

Taking the data you have, for a 35,000 gallon pool, a 1.5ppm FC rise takes 7oz or 0.43 pounds of chlorine gas (using PoolMath). You generated that in 7 hours -- over 24 hours your SWCG would generate 1.5 pounds per day ((0.43 / 7) * 24). If the actual rise was closer to 2ppm, that would be 9.3oz or 0.58 lbs of chlorine gas, corresponding to 2 lbs/day. I know Circupool claims 3.1 lbs/day, but prior threads have called those claims into question with similar results (50-60% of claimed). If you wanted to do another overnight gain test using careful 25ml samples and as long a runtime as you can manage, we can update the calcalations.

For dialing-in purposes, that means it takes around 4.5 hours of 100% runtime to raise 1 ppm. CYA level makes a big difference in usage -- with a high enough CYA level as recommended here for SWCGs (70-80ppm), I see 2-2.5ppm a day FC loss here in a full sun, hot temperature zone.. When my cover is off, I dial that in with 8-10 hours of runtime with my generic Calimar 40k SWCG (that generates around 1 pound/day as tested).

Sorry to get so wordy, but wanted to back up the calculations.

 

[talsayon]

Love it, thanks for all of that, I can appreciate the details. That's going to force me to run my pump about 12 hours a day at 100% which is a bit more than I wanted but not the end of the world. I've got my CYA up to 70 but I may consider bumping that up another 10ppm if it would help. I'm not sure how they can get away with claiming a rating that is 50% higher than what is actually achieved in real world setting, I'll have to reach out to their support and see if I can get anything out of them (I'm sure they'll be no help). I may do another test this weekend with the more precise 25mL sample and see how that turns out.

 

[talsayon]

Back at it trying to figure this all out as I'm now having to run it 19 hours a day. I just did an FC loss test today without the SWG running and went from 12 measured at 5am this morning, to 7 measured at 10pm this evening, for a total loss of 5 FC. CYA is a pain to measure so maybe I'm lower than I think. I'll try to take that up some because 5 FC feels like a lot and having to run my single stage pump for 19 hours a day just seems a bit ridiculous.