SWG has suddenly reduced Chlorine production

[geonjay]

Hello. I have a Hayward 925 SWG. It's been running for about 3 weeks, and I finally nailed down the schedule to keep me at an FC of 5ppm. The SWG runs for about 4 hours/day at 25%; broken into 2 cycles.
Our heater has been in place since the build, but just recently got the gas hooked up - we were waiting on the 2# meter. Started the heater last Thursday and within 6 hours we went from 68F to 89F and it was GLORIOUS. We swam on Friday, and had a few neighbors over on Saturday and Sunday. I noticed on Sunday that the FC was ~2.5 at 9am. I ASSumed it was possibly the high bather load (there were 5 people in the pool at max for all 3 days). Yesterday I tested at 8pm - still 2.5. So I turned on a 3rd cycle of 25% for 2 hours. I just tested at 8am (before the sun hits the pool) and it's still an FC of 2.5.

I haven't taken the cell out for inspection yet (I've never done that before) but I wanted to ask the forum before I touched anything else. Could the heater have somehow impacted the SWG? Is it expected to have reduced production after blasting it with hot water for a few days? The heater hasn't been on since Sunday afternoon.

 

[ajw22]

Nothing wrong with your cell other then you need to run it longer.

In your 15,000 gallon pool running your T-9 cell at 25% for 4 hours will generate 0.3 ppm of FC. A cycle of 25% for 2 hours will only give you 0.15 ppm of FC.

Try running your cell for 75% for 8 hours to get 2 ppm of FC.

What is your CYA?

Do you have PoolMath ?

 

[geonjay]

I try to run as close to the TFP recommendations as possible. My CYA is ~65ppm and I do use PoolMath. The SWG has been running for 3 weeks. I was testing twice daily when I first started it up; I've been testing every other day for the last 2 weeks. It has held 5ppm with no changes to the schedule in 2 weeks - why would it suddenly change? I'm using the same testing kit I've used since the beginning and I pull water from the same spot ~18" down.

 

[ajw22]

Your CYA is 70. We always round up.

2 weeks is not enough time to learn your pool environment and dial in your SWG. FC daily demand depends on the weather and varies during the seasons.

Crank up your SWG cycles.

 

[proavia]

What exact test kit are you using? Please add that info to your signature.
Also, share your PoolMath logs here so we can see them.

 

[Mdragger88]

After large bather loads & such supplement with liquid chlorine & then allow the swg to maintain. They aren’t very good at playing catch up.
To rule out organics eating up your fc since you have been below min for your cya you could do an Overnight Chlorine Loss Test.

 

[geonjay]

PoolMath Logs
In looking at the pool math logs I can see that I didn't add ALL of my results to the app every day. I'm keeping a notebook with the results. I've updated my signature to include my test kit - Taylor K2006-C + K-1766 salt, all chems are well within their expiration dates. Once I have the FC back up to the recommended TFP level (target of 5, min of 3) I'll try the OCLT.

Pump currently runs @ 64% for 5 hours, off 3 hours, on 5, off 3, on 5 = 15 hours run + 9 hours rest / day (This may be overkill, I'm trying to find the sweet spot for skimming).

Looking at my notes I started the SWG on 10/01 and I stopped using the bleach/dichlor (which I was using to get my CYA up). Running @ 40% 12 hours/day - running for 4 hours in the middle of each pump run time. On 10/3 my FC was 6.5.
10/5, 10/7, 10/9 = FC 6.5. I stopped the 8pm-12am chlorination cycle.
FC was then running between 5.0 and 5.5 - 5.0 if I tested at 5pm; 5.5 at 8am. This held until this weekend. 2 changes - 1) the pool heater was started and 2) People were swimming because the water wasn't frigid.
The last 2 days I've tested twice a day - the FC is holding at ~2.5ppm.

 

[ajw22]

Pump currently runs @ 64% for 5 hours, off 3 hours, on 5, off 3, on 5 = 15 hours run + 9 hours rest / day (This may be overkill, I'm trying to find the sweet spot for skimming).

You should run your pump at a low speed that keeps the SWG generating for 15 hours straight. I don't know what you are looking to accomplish by the on/off cycles. Set the pump to ramp up to a higher speed when you want for skimming.

Your Aquarite has a 180 minute (3 hour) generation cycle. Turning the generation on and off after every 5 hours you are messing up the cycling.

SWG Generation Cycle Times - Further Reading

www.troublefreepool.com

At 70%, it will generate for 126 minutes and then it will stop generating for 54 minutes. While not generating, Prologic will say percentage met, or Aquarite will have the generating led stay on when the switch is in auto even when it's not actually generating. The instant salinity and the amps will be zero when not generating.

Then, it will reverse polarity and a new 180 minute cycle will begin.

Output is scaled back to 20% at 60° F and output stops at 50° F If the temperature is 60 degrees or lower the output percentage is 20% of the selected %.

 

[proavia]

You may be best served by using liquid chlorine to get your FC to the top of the target range. Right now at FC 2.5, you are below the bare minimum. You cou,d already have a nascent algae bloom in progress.

And once your SWG stops generating due to low temps, treat the pool as a non-SWG pool until temps rise in the spring to a level high enough to support your SWG operating normally.

 

[geonjay]

I don't know what you are looking to accomplish by the on/off cycles.

Thank you for the SWG link. What I'm trying to accomplish is a balance of skimming throughout the day while reducing power consumption. This is my first pool, I'm still figuring it out. Even with ALL of the very helpful information on this site, I'm still a newb with 0 experience in owning/maintaining a pool. I'm here to seek advice and NOT state that what I'm doing is correct, if I came across that way I apologize.

From the information you provided, it seems that you're saying I should run the pump and SWG for one long period instead of breaking it up. Does the SWG keep track of the run times between cycles? Meaning, if I run it for 4 hours, and it has a 3 hour cycle - will it start the next 4 hour cycle by continuing the remainder of the previous 3 hour cycle? I think I'm misunderstanding that.

 

[ajw22]

Does the SWG keep track of the run times between cycles? Meaning, if I run it for 4 hours, and it has a 3 hour cycle - will it start the next 4 hour cycle by continuing the remainder of the previous 3 hour cycle? I think I'm misunderstanding that.

No, the SWG resets and starts new. So you undergenerate or overgenerate is you stop it in the middle of a generation or rest cycle. You also get uneven use of the two polarities. It makes it more confusing to know what FC output you can expect.

 

[markayash]

Water temp also changes my fc demand.

 

[geonjay]

No, the SWG resets and starts new. So you undergenerate or overgenerate is you stop it in the middle of a generation or rest cycle. You also get uneven use of the two polarities. It makes it more confusing to know what FC output you can expect.

You've had me going down rabbit holes of SWG specs, and arguments about pump run times for the last few hours. I feel that I'm stuck in analysis paralysis - which is when I turn to people with experience - people like YOU. Should I look to run the SWG in minimum 3 hour windows - or at least multiples of 3 hours? I was thinking that breaking the pump run times up into smaller chunks would keep the surface cleaner via skimming - as opposed to running for 15 straight hours and then 9 hours of nothing.

The PB left the minimum pump setting at 40% - and I haven't monkeyed with that yet, I'm not sure exactly what that RPM equivalent is. At 40% my flow meter shows ~40gpm AND the SWG will run. What do you recommend running? Especially now that fall/winter is here and we wont' be swimming again until late spring. We don't plan on using a cover.

Water temp also changes my fc demand.

So...I felt dumb before..now I feel really dumb. The water temp since the SWG was setup/running has always been below 78F - the last week it was below 70F. From Thursday - Sunday evening it was 87+. It's now starting to come back down - it's 80F now. I was worried that the heater broke something - could I expect the FC demand to be that drastically different with a 20F temp difference? I KNEW demand went down with temp, but in my ignorance I was thinking 40F difference, not 10-20F. Thanks for turning that light on.

 

[ajw22]

You've had me going down rabbit holes of SWG specs, and arguments about pump run times for the last few hours. I feel that I'm stuck in analysis paralysis - which is when I turn to people with experience - people like YOU. Should I look to run the SWG in minimum 3 hour windows - or at least multiples of 3 hours? I was thinking that breaking the pump run times up into smaller chunks would keep the surface cleaner via skimming - as opposed to running for 15 straight hours and then 9 hours of nothing.

You have two levers to control your FC generation - pump runtime and SWG %. Many of us just run our pumps 24/7 at low RPM then adjust SWG %. The cost to run your pump will be less then $1/day.

Otherwise pick a pump runtime around what works and then play with the SWG % to generate the chlorine you need.

The PB left the minimum pump setting at 40% - and I haven't monkeyed with that yet, I'm not sure exactly what that RPM equivalent is. At 40% my flow meter shows ~40gpm AND the SWG will run. What do you recommend running? Especially now that fall/winter is here and we wont' be swimming again until late spring. We don't plan on using a cover.

You have to find the point where the pump flow is too low to engage the flow switch then add 5% to the pump. Turn down the pump speed and see at what point you get the NO FLOW message for the SWG then turn it up a bit. As your filter gets dirty you will require more pump speed so keep an eye on it.

So...I felt dumb before..now I feel really dumb. The water temp since the SWG was setup/running has always been below 78F - the last week it was below 70F. From Thursday - Sunday evening it was 87+. It's now starting to come back down - it's 80F now. I was worried that the heater broke something - could I expect the FC demand to be that drastically different with a 20F temp difference? I KNEW demand went down with temp, but in my ignorance I was thinking 40F difference, not 10-20F. Thanks for turning that light on.

There are lots of factors that effect daily FC loss so it is a moving target that changes every day. Follow the FC/CYA Levels and stay at the high end of your range for your CYA. I run my FC 1 to 2 ppm over high end. That gives plenty of room for the FC to not fall below the minimum and the SWG to catch up or me to see I need to adjust the SWG % a bit.

The SWG % is not a set and forever forget. You will be adjusting it about once a month up or down as the seasons change after you have it dialed in for your pool.

 

[markayash]

One lesson a lot of us have learned the hard way
Swg pools feel smooth so don’t shot for the min FC. I did and worked great for a few months then green and took weeks to recover. Now I keep it around 7.

 

[revitup]

One lesson a lot of us have learned the hard way
Swg pools feel smooth so don’t shot for the min FC. I did and worked great for a few months then green and took weeks to recover. Now I keep it around 7.

Some of us start to panic if we see 7 lol. 8-12

 

[wireform]

Geonjay,
By trying to dial it in the way you doing will create a monster algae bloom to kick in if it hasn't already in the background just by the low FC you're experiencing. As a new pool owner it's suggested to run the FC hot and then back it down slowly till you get the feel for it. The SWCG is to maintain the pool for the daily loss and not even for heavy bather loads which we then recommend liquid chlorine as insurance for a heavy drop in the FC. Do a OCLT today to give you a reality check if in fact there's algae in the works which will mean for you to slam to bring it back. Myself and many others here run the FC at least 2ppm more then the high side of the target for a given CYA level. By skirting the fence with just barely reaching the FC needed you cause what you have going on now. Please take this as critique as we're here to help you along.

 

[jseyfert3]

It sounds like a mix of both hotter temps which will cause greater loss of FC by themselves combined with bather waste. Nobody was swimming, then you heated up the water and people were swimming. So hotter temps and bather waste.

 

[Mdragger88]

I like to keep my fc at least @ 10% of my cya all the time . It’s a good buffer that allows for wiggle room. Did your heater happen to have stagnant water in it? This + bather load could have easily consumed your fc & allowed u to fall below min. Now you’re playing catch-up & possibly have an organics issue. Good thing is that since u test frequently you caught it early & can avoid a green monster. You’ll be back on track in no time

 

[Newdude]

Hey Jay !!!

You've had me going down rabbit holes of SWG specs, and arguments about pump run times for the last few hours. I feel that I'm stuck in analysis paralysis - which is when I turn to people with experience - people like YOU

Looks like we have a classic case of over management going on, and we’ve ALL been there with our new found skills. You’re trying to combine things that are separate entities and shooting yourself in the foot in the process. Like splitting up the SWG runtime to increase skimming potential at different times. It sounds great on paper until it alters the SWG cycle because the times you chose don’t line up with the SWG cycle, making your XX% really be YY% which will be too much or not enough.

So the KISS principal applies here. Need FC production ? Run the SWG to achieve it. Need more skimming/ filtering ? Add that as a separate entity with the SWG off at that time.

Or Keep It Stupid Simple, Stupid. (KISSS ). There are far to many benefits of running the pump 24/7 to list and almost no negatives. You’ll only have to adjust cell % instead of both cell and pump. You’ll skim and filter full time and if a storm hits overnight, you are mixing already. If crud falls on a windy afternoon….. yup. You got that covered too already skimming. Filtering becomes a non issue as you’re always at your cleanest. And pumps don’t like the on/off cycle. it takes many many cycles to harm it, but it takes that much longer if you only cycle the pump a few times a year for maintenance like filter cleanings. Commercial pumps that never shut off will run for decades sometimes.

The only downside is about $20 a month on the electric bill. Mere peanuts as you already pay something to run the pump. So maybe it’s only $12 more. I feel so strongly about 24/7 I would gladly pay 4 years upfront to do so. Here ya go…. $400. Now leave me alone while I *dont* care about everything that most have to care about.

The same goes for target range. If you want to watch your FC like a Hawk you can cut it as close to minimum as possible. I targeted 10 and usually overproduced. I had a few days reserve FC at all times. It burns off a little quicker as a % at higher levels, so maybe I ‘wasted’ 1/3 of my FC. I was willing to trade that for never having to care about UV, daily loss, heavy rain, debris, etc.

If I told anyone that they could never care about algae for $50 (?) in wasted chlorine a year and maybe $10 extra in monthly electric, most folks would have dug it out of their pocket before I finished my sentence.