Secondary SWG

[scatkins]

I've been searching for discussions on adding a second salt generator to my pool, but haven't seen much.. I know they exists as I see Pentair has a commercial setup where they parallel multiple SWGs in commercial applications..

My situation is pretty common. My Pentair IC40 just can't keep up when it gets hot and sunny (central Florida).. It does "ok" for most of the year although I have to run it at greater than 50%, but as soon as it starts getting hot, muggy and sunny, even running at 100% won't keep up. I will admit I was hesitant at first to run the CYA at the higher levels I am now (70-80ppm), and that did seem to help as I'm keeping more chlorine in the pool than previously. But a couple hot days and I'm having to supplement with liquid chlorine. I stay on it and have never had any signs of algae. I pull the cartridge from the filter every couple weeks and clean... Have swapped in a new cartridge as well.. Run a Dolphin robot a few times a week and keep the pool pretty much spotlessly clean. The pool is somewhere between 13000 and 14000 gallons.

This post is really intended to address how to best install a secondary SWG and not if I should needed to.. But since I'm sure the question will come up my pool chemistry is generally fine.. CYA ~ 70-80, PH is stable in range of 7.4 to 7.6, salt level ~ 3600ppm, Total alkalinity ~100ppm, CA hardness ~ 200... Have gone through the SLAM process periodically... Combined Chlorine is usually pretty decent and stays below 0.2 or 0.3 ppm. Any higher than that and I shock or SLAM the pool. I'm fairly confident in the chemistry numbers as I check daily both with regents and a Lamotte spin-tester. Pool isn't subjected to contaminates as it is in a patio screen enclosure so it doesn't see a lot of bug, leaves or other stuff..

For the most part the chemistry is good, the pool is clean and the water is clear.. The IC40 just can't keep up with hot days.. even though it is a relatively small pool. The IC40 is relatively new and seems to generate chlorine fine when it is not so blasted sunny.. So it appears to be functional. Also I've played with flow rates, and installed a mechanical flow rate indicator as well as I get flow feedback through my Pentair Easytouch on the GPM for the Variable Flow Pump. The IC40 seems to generate chlorine just fine above about 19 GPM (spec is min of 25 or 26 GPM). But I've been running my pump in the 30 to 35 GPM range to make sure low flow wasn't the problem.

So, chemistry wasn't the point of my post, but I figured I'd first go through that because I know the first assumptions was that I probably had a higher chlorine demand due to some pool chemistry or other incompetence with the SWG on my part. But I've had pools for a lot of years and never had chemistry or chlorine level problems, but I am new to Hot sunny Florida which places some pretty heavy demand on chlorine.

So what I want to do is add a second chlorine generator. I could replace the IC40 with an IC60, to get more generation capacity but figured If I have to buy another SWG, then I might as well use them both.. My Pentair Easytouch can only control one SWG, but I can manually control the second.. My plan is during the cooler season just run one SWG (as that currently works ok) and then manually turn on the secondary only during the hot months and try to balance the generation from the two to maximize cell life. In the end I want to get away from having to manually add liquid chlorine to the pool or having a floating chlorine puck duck..

So the question is... Should I be installing these in two parallel or in series? The Pentair commercial setup I've seen seem to put them in parallel. But if I put them in parallel then it means I have to run my pump at a higher (and much less efficient speed). So if the min is 25 GPH for one SWG to work, I'd have to run the pump at 50 GPH (which for my system works out to be about 2900 RPM) for both parallel SWGs to generate chlorine...

I know there is a concern with "bubbles" generated by the SWG, but I have enough room on my pad that I could spread the two series SWGs by 2 or 3 feet or more if needed.

I'm thinking I might run them in parallel, and have a blocking valve in front of the secondary unit, that way I only have to run the higher flow when I want to use both SWGs, so at least most of the year I can run the pump more efficiently.

Anyone have any real experience with multiple SWGs?

Thanks in advance.

 

[Newdude]

Welcome scat. If you don’t mind me tagging along to learn some with you, I’m in too.

 

[proavia]

Maybe I missed it, but I didn't see how many hours per day you are running the pump.

An IC40 should be more than enough for a 15,000 gallon pool - even in Florida in the summer. Have you done an Overnight Chlorine Loss Test to rule out a possible algae issue. I also don't see an FC/CC reading

Can you fill out your signature with details of your pool and equipment, including your test kit?

 

[ajw22]

Read SWG Multiple Cells - Further Reading

I agree that an IC40 should handle a 15,000 gallon pool with no problems. I ran a IC40 in a 35,000 gallon pool.

Have you done a Overnight Chlorine Loss Test?

I hate to bring up the P word but you may want to test your water for phosphates and tell us what level you get. We have heard SWG manufactures say that high phosphates blocks SWG output. Some Florida areas have got high phosphates due to agricultural runoff.

If you insist on going a second cell connect it serial in the water flow.

 

[Jimrahbe]

The pool is somewhere between 13000 and 14000 gallons.

S,

Either your cell is bad (and I doubt it) or something is dreadfully wrong..

How many hours a day do you run the cell?

Before going crazy I suggest that you do this..

1. Run the standard Overnight Chlorine Loss Test with the cell off... Overnight Chlorine Loss Test

2. Assuming you pass the OCLT, run the same test, but with the cell on.. This will tell you how much FC your cell will produce per hour. This then tells you how many hours you must run, your cell, in your pool, to generate the chlorine you need.

Thanks,

Jim R.

 

[scatkins]

Read SWG Multiple Cells - Further Reading

I agree that an IC40 should handle a 15,000 gallon pool with no problems. I ran a IC40 in a 35,000 gallon pool.

Have you done a Overnight Chlorine Loss Test?

I hate to bring up the P word but you may want to test your water for phosphates and tell us what level you get. We have heard SWG manufactures say that high phosphates blocks SWG output. Some Florida areas have got high phosphates due to agricultural runoff.

If you insist on going a second cell connect it serial in the water flow.

1) Phosphates are at 0....
2) Overnight chlorine loss is minimal... less than 0.5 ppm..
3) Yes agree an IC40 should handle the pool size.. But it doesn't... It is fine until I get to a the first few super Hot sunny days.. then it just can't seem to keep up.. I kept thinking there must be some kind of contaminates, but nope... just seems like the sun here is just too intense.....

Thanks, I'm leaning towards serial...

 

[scatkins]

S,

Either your cell is bad (and I doubt it) or something is dreadfully wrong..

How many hours a day do you run the cell?

Before going crazy I suggest that you do this..

1. Run the standard Overnight Chlorine Loss Test with the cell off... Overnight Chlorine Loss Test

2. Assuming you pass the OCLT, run the same test, but with the cell on.. This will tell you how much FC your cell will produce per hour. This then tells you how many hours you must run, your cell, in your pool, to generate the chlorine you need.

Thanks,

Jim R.

Right now I'm running the pool and cell probably 10 or 11 hours a day.

OK, I like that idea... I'll give that a try to determine how much chlorine is being generated per hour...

 

[scatkins]

Maybe I missed it, but I didn't see how many hours per day you are running the pump.

An IC40 should be more than enough for a 15,000 gallon pool - even in Florida in the summer. Have you done an Overnight Chlorine Loss Test to rule out a possible algae issue. I also don't see an FC/CC reading

Can you fill out your signature with details of your pool and equipment, including your test kit?

I've been playing around with the run time on the pool, but at least 11+ hours a day... Well my overall problem is just keeping FC at a reasonable level. Right now I'm having a hard time getting even getting FC to 1.0 without supplementing with liquid. At my last reading before starting to SLAM was FC at about 1.0 with CC at about 0.4. The the TC/FC seem to deteriorate late in the afternoon.. The CC never really climbs that much..

The last overnight I did was less than a 0.5 loss. But one of the suggestions was to perform with and without the pump/chlorinating which I'll try to see what the output really is.

 

[proavia]

In parallel you will need about twice the flow as in series - as you have to close both flow switches which are in parallel pipes. In series the flow will be about the same as running one SWG/flow switch cause all the water into the 2 SWG will be in one pipe.

I still believe you can use your one IC40 to maintain your FC. What CYA are you running? Have you been following the FC/CYA Levels ? If you have heavy bather load, you may have to occassionally supplement with liquid chlorine.

 

[Rossterman]

What’s your salt level? Verify with a proper test kit not the swg reading. Lower end on salt concentration seems to impact production. I was running my pool last year and facing similar issues as you. I always liked to keep salt concentration at the bottom end of the range. This year I elevated the salt level to near the high end of the range and I’ve had to crank the cell output down to stop over chlorinating

 

[JJ_Tex]

Use pool math to see what your IC40 should be generating.

I did a couple of variations below, using 15k pool and the IC40 and you can really see the difference when you increase your run time:

FC of 3.7 generated daily - 80% @ 10 hours a day
FC of 2.8 generated daily - 60% @ 10 hours a day

FC of 6.7 generated daily - 80% @ 18 hours a day
FC of 5.0 generated daily - 60% @ 18 hours a day

FC of 8.9 generated daily - 80% @ 24 hours a day
FC of 6.7 generated daily - 60% @ 24 hours a day

Since you have a variable speed pump, run it on a low RPMs 24/7 and you should be able to generate the chlorine you need and use a minimal amount of extra electricity. That should be a much cheaper and easier solution to get you the chlorine you need.

 

[Hootz]

Either your chlorine is being consumed abnormally fast or your ic40 is not working properly. 10 hours at 100% should produce about 4.7 fc. One swg should be able to supply a pool of your size.

 

[scatkins]

In parallel you will need about twice the flow as in series - as you have to close both flow switches which are in parallel pipes. In series the flow will be about the same as running one SWG/flow switch cause all the water into the 2 SWG will be in one pipe.

I still believe you can use your one IC40 to maintain your FC. What CYA are you running? Have you been following the FC/CYA Levels ? If you have heavy bather load, you may have to occassionally supplement with liquid chlorine.

As in my initial post I'm running CYA at about 70, which admittedly has helped. Pool is lightly used, so no real human contaminants introduced.

 

[scatkins]

What’s your salt level? Verify with a proper test kit not the swg reading. Lower end on salt concentration seems to impact production. I was running my pool last year and facing similar issues as you. I always liked to keep salt concentration at the bottom end of the range. This year I elevated the salt level to near the high end of the range and I’ve had to crank the cell output down to stop over chlorinating

salt concentration is in the 3600 to 3800 range and measured via exech electronics, test strips, my Lamotte Spin test and the SWG... So I don't anticipate any issues there.

 

[scatkins]

Use pool math to see what your IC40 should be generating.

I did a couple of variations below, using 15k pool and the IC40 and you can really see the difference when you increase your run time:

FC of 3.7 generated daily - 80% @ 10 hours a day
FC of 2.8 generated daily - 60% @ 10 hours a day

FC of 6.7 generated daily - 80% @ 18 hours a day
FC of 5.0 generated daily - 60% @ 18 hours a day

FC of 8.9 generated daily - 80% @ 24 hours a day
FC of 6.7 generated daily - 60% @ 24 hours a day

Since you have a variable speed pump, run it on a low RPMs 24/7 and you should be able to generate the chlorine you need and use a minimal amount of extra electricity. That should be a much cheaper and easier solution to get you the chlorine you need.

Yes I understand that chlorine generation is proportional to the run time. And to a certain extent I've extended my run times to try and get a little more output. But doubling a 12 hour to 24 run time is not an economical way to do it.. Per pentair spec, I need to run at at least 25 GPM per Pentair to make chlorine .. At that flow rate the pump is running at about 1750 RPM.. / 285W... Not awful but certainly not low RPM..... At 25 GPH I turn the water over in less than 9 hours. So to run it 24/7 at the lowest possible rate that will make chlorine would turn the water over much more than needed.. and is wasting a lot of energy..

Though some experimentation I found my IC40 will make chlorine down at a flow rate of 20 GPH/1490 RPM... I'm not sure how efficient it is at that flow rate so that is probably about the lowest flow I can count on... and at that rate I still turn over in about 10.1 hours. I can run the pump down to about 750 RPM, which is very economical from the perspective of turning the water over, but It won't make chlorine at that speed.

Thus I'm back to my original purpose of the initial post to running multiple units as a more economical alternative.

 

[Jimrahbe]

S,

You do realize that the idea that you have to turnover X water per day is just a myth... right???

You just need to run your pump long enough to generate the chlorine you need.. Period.

The IC40 makes the same amount of chlorine no matter what the pump speed is, as long a the flow switch is closed.

Thanks,

Jim R.

 

[scatkins]

Either your chlorine is being consumed abnormally fast or your ic40 is not working properly. 10 hours at 100% should produce about 4.7 fc. One swg should be able to supply a pool of your size.

Maybe, I'm not convinced about the abnormally fast part as it seems to be an issue with most I've talked to down here. Upping the CYA has helped.. But I'm going to test the IC40 output as was suggested in an earlier post. That said I'm fairly certain my IC40 is working ok as it generates tons of FC in the winter time...

 

[Jimrahbe]

S,

Keep in mind we have a ton of members that live where you live and none of them seem to have extra hot sun beams..

Jim R.

 

[scatkins]

S,

Keep in mind we have a ton of members that live where you live and none of them seem to have extra hot sun beams..

Jim R.

I appreciate that.. although none on this thread as yet.... And as I've talked to my local "professionals" every one of them has told me... "oh yeah... I would have installed an IC60 as everyone has a hard time keeping up in the summer".... Anecdotal at best I understand.

But also keep in mind the purpose of my post wasn't to debate pool chemistry and if my setup was adequate ... I am appreciative and respectful of the good input, But my intent was really to address serial vs parallel SWG install.

 

[mguzzy]

I just read through this thread.. Interesting problem to figure out. To answer your question. YES an IC40 is more than adequate for a 13K pool... and YES you can install multiple SWG's in parallel. Some controllers support that, some don't so you would have to add a second controller....

That said what else could be chewing up your FC in hot conditions. .. that what's what it boils down to.. You can throw more FC in there via jugs of LC or 47 SWG's wired in parallel to compensate but, we still haven't solved the mystery of were the FC is going. You say it happens when it gets hot or when it gets sunny? those are two different conditions.

So to throw my 2 neurons worth of brainstorming into the mix, I am reminded of the pool owner that could not figure out where is chlorine loss was until he posted some pics of his custom water features and sculpturer friend of his did (or something like that). But it turns out they had large bowls that retained water in the water feature and were a perfect breeding ground for algae growth. Do you have some kind of water feature or something attached to the pool that would behave that way?