Went from being saltwater curious to a bit confused about my chlorination identity

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JayG

JayG

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Aug 31, 2015
214
Harrison, NY
I have been a Stenner chlorination guy for the last 3 seasons but had gotten lazy about schlepping bottles of bleach, so I took the plunge and installed an RJ60+ this season. The install was a breeze and after adding 800 lbs of salt to our pool (based on the Taylor test kit), I was getting the following:

FC 5 (added some leftover dichlor to up my CYA and chlorinate)
CYA 50 (a bit low, but planned to add some more CYA)
CH 200 (working to fix that)
TA 70
pH 7.5
NaCl 3200 (a bit low, but planned to up that later)
Borates 30
Water was clear and 68°F

So, I turned on the SWG cell and thought all was well. I decided to start with 50% run time (I have a VSP that I run 24/7 at low speed) thinking that I wanted to ward off any algae problems during the transition. The SWG appeared to be working fine: flow ok, bubbles coming out of the cell, etc. However, the next day the FC was still 5. Our pool traditionally needs about 2ppm of FC per day. So, I thought that I should have increased my FC more than that, but I didn't panic. I buffed up the chemistries adding CaCl2, NaCl, and some more CYA. Cell continued to run at 50% for 24 hours.

I came back and found:

FC 3
CYA 65
CH 420
TA 70
pH 7.5
NaCL 4200

So all my chemistries are going in the right direction, but my FC (no detectable CC BTW). Pool still looked great (clear, etc.) Of course, Circupool included a Phosphate test kit (my reading is 2500 ppb) and claims that this may be the problem. However, the collective wisdom on this site says this is BS and that I might have a cryptic algae problem. So, I added some bleach and got my FC to 24.5. I did an OCLT and did not have any loss of FC (SWG turned off overnight). I have to say there is something satisfying about adding the bleach and seeing a predictable effect. I was now beginning to question my decision to move away from my trusty Stenner, but I'm invested in salt water now and want to make this work. So, I turned on the SWG again this morning and I will check again when I get home.

Any thoughts about what might be going on?

Perhaps my problem will be solved post SLAM/OCLT (as others have reported). But I don't understand the low output I've seen thus far, and I don't think I had a cryptic algae problem based on OCLT results.

Could it be the low water temp (68°F)?

Should I have waited for the FC to come down before restarting the SWG cell?

I'm in uncharted waters for me and am a bit confused. Any words of wisdom are appreciated. Thanks!
 
SWGs are great at maintaining FC, not so much at building it up from nothing. So we do what you did, boost FC to target, then switch on the SWG.

When you first turned it on and FC was 5, what time did you turn it on, and what time did you test again the next day?
 
kellyfair said:
SWGs are great at maintaining FC, not so much at building it up from nothing. So we do what you did, boost FC to target, then switch on the SWG.

When you first turned it on and FC was 5, what time did you turn it on, and what time did you test again the next day?
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Thanks Kelly,
I left out a few details for brevity. I believe I started the SWG in the evening with an existing FC of 5 and checked it twice in the morning over the next 48 hours (FC steady at 5) before upping the CYA, NaCl and the CaCl2 when it then dipped to 3 24 hr later. I originally thought that maybe the SWG needed higher salt concentration to reach its rated output, so I was surprised when it actually fell. This morning the FC was 24.5 (as it was last night) after adding bleach yesterday afternoon.
 
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So, it was keeping your FC at 5, even during the day. So we know it is working. Curious about what your manual says as to expected output, and also how much salt is recommended.

Someone more knowledgeable than I am will likely be along soon, but for now, I would tweak the percentage until it is producing enough chlorine to meet your target. Also, you should consider your CYA 70, as it is measured by tens, not by fives.
 
Philo said:
If the OCLT is fine, I'd start the SWG at 100% and work my way down.
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Right now I'm at 24.5 FC after doing a mini-SLAM. I started the SWG this morning at 80% which should be producing about 8 ppm of FC for our pool per day. I'll do another OCLT tonight to be safe (and see where FC is at after 12 hr at 80%). It is cloudy today, so it should give the SWG a chance to catch up.
 
The SWG should have been adding 6ppm of FC each day at 50%. That is more than enough for now, don't bother with 100%.

Let the FC drop to around 10 and then turn the SWG back on.

Are you changing the pump speed? You might be too low for it to produce so make sure you are testing it with a speed that produces chlorine.
 
kellyfair said:
So, it was keeping your FC at 5, even during the day. So we know it is working. Curious about what your manual says as to expected output, and also how much salt is recommended.

Someone more knowledgeable than I am will likely be along soon, but for now, I would tweak the percentage until it is producing enough chlorine to meet your target. Also, you should consider your CYA 70, as it is measured by tens, not by fives.
Click to expand...

Circupool states that the RJ60 can output 3.1 lbs of Cl2 per day. I don't have it in front of me, but one of the members did an Excel calculator which indicated that 20% runtime per 24 hours should yield 2 ppm/day of FC in our pool. And yes, the CYA dot disappeared between the 60 and 70 mark, but it's safer to assume 70 and adjust FC based on that.
 
ping said:
The SWG should have been adding 6ppm of FC each day at 50%. That is more than enough for now, don't bother with 100%.

Let the FC drop to around 10 and then turn the SWG back on.

Are you changing the pump speed? You might be too low for it to produce so make sure you are testing it with a speed that produces chlorine.
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Hi Ping, I've dialed in a flow rate that activates the flow switch for the lowest pump speed. I sometimes increase the speed if I'm trying to mix things up or after a rainstorm to help the skimmers. Your numbers basically agree with mine as to how much FC I expected to make. I'll turn the SWG off when I get home tonight and do another OCLT.
 

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Make sure you give the pump speed some extra room, don't keep it at the minimum. The pump guru's recommend no lower than 1000 RPM on variable speed pumps as there isn't much to be gained by running it slower than that.
 
ping said:
Make sure you give the pump speed some extra room, don't keep it at the minimum. The pump guru's recommend no lower than 1000 RPM on variable speed pumps as there isn't much to be gained by running it slower than that.
Click to expand...

I'll double check, but I believe my lowest speed is 1250 rpm. That shows about 20 gpm on my flow meter.
 
That could be near the low end range for the RJ, when you run the SWG again I would bump it up to 25 GPM to be sure to eliminate the flow as the reason for not producing. I would hope that 20GPM is more than enough for that cell to work.
 
Philo said:
"The SWG should have been adding 6ppm of FC each day at 50%. That is more than enough for now, don't bother with 100%"

Ping, did you get the "6ppm of FC each day at 50%" based on Circupools "claim" that it produces 3.1 lbs./day?
Click to expand...

I've read that some folks think that the output claims of Circupool are fanciful. I considered that possibility as well as an explanation of my unexpectedly low output. Too early to say.
 
Just an update. Came home after dark and turned off the SWG (running at 80% for 12 hours) and TC was 19.5. CC 0. This is down from 24.5 this morning. Granted it rained most of the day, so that may have used up some FC, but I had no CC. On the other hand, it was cloudy...so sunlight was not a big player. On the other, other hand...the SWG running at 80% for 12 hours did not keep TC or FC up where one might of expected. I will use the last reading to do another OCLT tomorrow morning.
 
Why are you trying to keep your chlorine so high... are you trying to SLAM? If so, I wouldn’t try to use your SWG for that.
 
kellyfair said:
Why are you trying to keep your chlorine so high... are you trying to SLAM? If so, I wouldn’t try to use your SWG for that.
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Hi Kelly, Not knowing better, I turned it on (as I said earlier) after the OCLT this morning just to see if I could keep up a SLAM level of FC. It didn't work. I keep thinking that turning on the SWG was like when I was turning on the Stenner to add bleach. I'm learning (for reasons I don't yet understand), SWGs don't work like that. So, it is off now until the FC levels get below 10. And for the record, low flow does not appear to be an issue.
 

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