Chlorine output from SWG

[cabber]

I'm still trying to figure this out so any assistance is greatly appreciated. I have the Jandy Aquapure SWG and not sure it is producing the proper clorine level. I have the salt production set at 70 percent and the pump running eight hours per day. My pool is roughly 25,000 gallons.
I've had the Aquapure running this way for the past four days and when I checked my chlorine level it was almost non existant. My CYA is fine as is my ph level. My salt level is reading at 3000PPM. Can you get a faulty salt cell or are they pretty much the steady part of the equation? I checked it to see if it was dirty or had any calcium build up and it looked brand new. I've only had it for a few months. Any thoughts.

I've even tried to measure the chlorine from the returns to see if it is coming out and get no change in readings. Keep in mind that the pool temp is 74 and has no swimming activity at all. Thanks.

 

[divnkd101]

I'm still trying to figure this out so any assistance is greatly appreciated. I have the Jandy Aquapure SWG and not sure it is producing the proper clorine level. I have the salt production set at 70 percent and the pump running eight hours per day. My pool is roughly 25,000 gallons.
I've had the Aquapure running this way for the past four days and when I checked my chlorine level it was almost non existant. My CYA is fine as is my ph level. My salt level is reading at 3000PPM. Can you get a faulty salt cell or are they pretty much the steady part of the equation? I checked it to see if it was dirty or had any calcium build up and it looked brand new. I've only had it for a few months. Any thoughts.

I've even tried to measure the chlorine from the returns to see if it is coming out and get no change in readings. Keep in mind that the pool temp is 74 and has no swimming activity at all. Thanks.

What are you using to check your levels? Is this a new pool, existing switchover, etc.?
I like to keep my salt level above 3200. Another bag of salt may not hurt your cause. I have mine set at 50% right now with my pool only operating 4 hours a day.
If you are still not sure of your readings, may I suggest taking a water sample to a local Pool Company. I am hopeful that the ones in your area will provide you with a free analysis. Good luck and keep us posted.

 

[SeanB]

I'm still trying to figure this out so any assistance is greatly appreciated. I have the Jandy Aquapure SWG and not sure it is producing the proper clorine level. I have the salt production set at 70 percent and the pump running eight hours per day. My pool is roughly 25,000 gallons.
I've had the Aquapure running this way for the past four days and when I checked my chlorine level it was almost non existant. My CYA is fine as is my ph level. My salt level is reading at 3000PPM. Can you get a faulty salt cell or are they pretty much the steady part of the equation? I checked it to see if it was dirty or had any calcium build up and it looked brand new. I've only had it for a few months. Any thoughts.

I've even tried to measure the chlorine from the returns to see if it is coming out and get no change in readings. Keep in mind that the pool temp is 74 and has no swimming activity at all. Thanks.

I'd start by getting the salt level tested, either yourself at at the pool store.

 

[Alpha_Bear]

Cholrine *drools* *cough back to reality* yer i have no place in this forum as im english and we have as much "pool season" as we do nice weather! lol any way...yer cholrine is very interesting chemicaly but thats off-topic lol

YAY chemistry!

T.B.C

 

[cabber]

I'm still trying to figure this out so any assistance is greatly appreciated. I have the Jandy Aquapure SWG and not sure it is producing the proper clorine level. I have the salt production set at 70 percent and the pump running eight hours per day. My pool is roughly 25,000 gallons.
I've had the Aquapure running this way for the past four days and when I checked my chlorine level it was almost non existant. My CYA is fine as is my ph level. My salt level is reading at 3000PPM. Can you get a faulty salt cell or are they pretty much the steady part of the equation? I checked it to see if it was dirty or had any calcium build up and it looked brand new. I've only had it for a few months. Any thoughts.

I've even tried to measure the chlorine from the returns to see if it is coming out and get no change in readings. Keep in mind that the pool temp is 74 and has no swimming activity at all. Thanks.

What are you using to check your levels? Is this a new pool, existing switchover, etc.?
I like to keep my salt level above 3200. Another bag of salt may not hurt your cause. I have mine set at 50% right now with my pool only operating 4 hours a day.
If you are still not sure of your readings, may I suggest taking a water sample to a local Pool Company. I am hopeful that the ones in your area will provide you with a free analysis. Good luck and keep us posted.

Im using a TEST KIT from Leslie's POOLS. DPD Test Kit. Tests for Free and Total Chlorine, pH, Acid, TA, Calcium Hardness, CYA.

This is a new pool that was completed in November 2006. I initially shocked it will bleach, and used bleach a few other times throughout the winter. To check the salt levels I am using the taylor salt test kit. My salt shows levels between 3000 and 3100 based on water temperature variation. I've had the filter/pump running eight hours per day for the last two weeks, with chlorine output at 45-50 percent. When I chaceked the Chlorine level it was barely shwoing up on the scale.

 

[Guest]

when you say your CYA and pH are fine what do you mean? "Fine" is not actually a water quality measurement that gives a lot of information about what might be going on in your water. It would be most helpful if you could post a full set of test results for all water parameters.

 

[cabber]

when you say your CYA and pH are fine what do you mean? "Fine" is not actually a water quality measurement that gives a lot of information about what might be going on in your water. It would be most helpful if you could post a full set of test results for all water parameters.

Sorry about that. Just ran the test to represent data as of today. Keep in mind, I have had the pump running for the past ten days from 8:00 AM - 4:00PM with no swimming activity. No sunshine either. It's been cloudy and mild here in Texas. The SWG has been set to 70 percent output and these are the results.

FC- 1
TC- 1
CC- 0
pH- 7.4
TA- 80 PPM
CH - 240
CYA- 30

 

[crazycanuck]

Could it be that over the winter your chlorine has been eaten up and your SWG isnt on long enough and can't overcome that break point of Chlorine consumption vs. output. What about shocking the pool with Bleach to get your FC up to 6ppm and see if your SWG can keep it up over the next week.

 

[crazycanuck]

I also had that issue on my startup and found out I didnt have enough CYA. Maybe you should have your CYA test double checked.

 

[cabber]

I also had that issue on my startup and found out I didnt have enough CYA. Maybe you should have your CYA test double checked.

Thanks fro the insight. What level do you run your CYA at? As you can see, mine is at the bottom end with 30.

 

[crazycanuck]

last summer I ran my CYA at 35ppm. I have a 14,000gal Inground with an SWCG. I was south facing with a lot of direct sun. On startup my CYA was 5ppm and whatever chlorine the pool started with in the morning was gone by the afternoon. Like you, it was barely neglible on the test kit and I was running the SWG at 60% and the pump was running 24/7... until I got my first electric bill :-O

Now, once I got my CYA up to 35ppm I was able to back off the SWG to 40%... and even down to 20%, and eventually I only had the pump on for about 14 hours of the day (I need to get a timer this year)

So if I were you, double check the CYA, and if it is indeed 30, then try shocking with Bleach to get up to 6ppm Chlorine and see if your SWG can sustain it, if it cant then it might be a salt or SWG problem. Maybe even try running your pump 24 hours for 4-5 days and then start taking down from there.

 

[Guest]

Most SWG manufacturers recommend between 60-80 ppm. I know of one that recommend 80-100 ppm and there are a few that recommend 50-80 ppm. I have found in my experience that not enough CYA in the water is a primary cause of low chlorine levels with high output settings. I would suggest finding out what the recommended range is from Jandy and try running your CYA in the middle of that range for starters.

Also, what is your water temp? Chlorine production drops off significantly as temperature drops.

 

[TheOne]

FWIW the Pentair Intellichlor manual says its important to be at 75ppm for CYA for their SWCG to work properly.

 

[crazycanuck]

Look like I better bring my CYA up this season

 

[cliff_s]

You might want to review the first thread in this group.

The higher the CYA the more chlorine you need for effective sanitation. With no CYA the chlorine would be gone in just a couple of hours. As you raise the CYA level the chlorine evaporates slower at the same time the chlorine becomes less effective. The table will show how much the chlorine level must be raised to be effective with the increase in CYA level.

Now for the dirty little secret about Salt Chlorine generators. Many manufacturers install units that are too small for the application and then run the CYA level up(some over 100 ppm) to cover up the low output of the unit. This of course limits the effectiveness of the chlorine, their answer is you must shock your pool at least 3 times a week. Of course if you shocked your pool 3 times a week you wouldn't need any additional chlorine.

Your unit should be able to to generate 3 ppm of chlorine with about 6 hours of run time and a CYA level of 50, with a pool water temp of 80 deg.. If your unit won't do this it is too small and you need a bigger unit. Many of the pool builders tell the customers that the filter must be run 24 hours a day if you have a salt generator. Again this is to cover-up too small a unit.

Cliff s

 

[Guest]

Actually, it is more probably that the higher levels of CYA are needed with a salt water generator because of the high concentration of HOCl that builds up at the cell. This will slow generation of chlorine down. If a higher level of CYA is present the HOCl will combine with the CYA to form chlorinated isocyanurates and allow chlorine generation to procede unimpeded. I have many customers with SWGs besides having one in my own pool and the one common factor is that the need to shock (based on having any measurable combined chloramines) is practically nonexistant! This has been echoed on all the other pool forums and boards that I participate in on the internet. Higher CYA levels cause more of the chlorine to be in the form of chlorinated isocyanurates, which are less effective sanitizers than HOCl but they act as a reserve to supply HOCl when the level in the water drops. I won't go into the chemistry here but if you want to read more about it you can go here.

 

[cabber]

Just to circle back around with this topic. I played around with the SWG system for several weeks with minimal success. Finally, I went and bought Conditioner/Stabilizer and upped the total CYA 50-60. I'm seeing a huge improvement with chlorine production in the SWG. I believe my CYA being in the 30's was the issue. It's only been a few days, but there is noe 2.0PPM in the pool.

 

[chem geek]

As can be seen in this graph, the half-life of chlorine in direct noontime sun is increased from about 6 hours to 7 hours when raising the CYA from 30 to 60 ppm. Too bad we didn't try experimenting with chlorine production overnight when the sun wasn't shining as that would have eliminated the degradation of chlorine from sunlight as a factor. It does seem that the SWG becomes more efficient at higher levels of CYA and as waterbear points out, there may be technical reasons for this that I explored in post #45 in this long thread on the Pool Forum. Since different users of SWG systems had somewhat different results, I have been hesitant to say that "higher CYA is required for SWG efficiency" was a true statement, but your experience plus the experience of others is having me lean towards that. It may be somewhat dependent on the specific design of the SWG cell with some needing more CYA than others depending on how much the water is "slowed down" in the cell (this is done to achieve higher localized chlorine levels for "superchlorination"). If the water is slowed down to achieve higher localized chlorine levels, then this excess build-up can slow down the cell's ability to produce chlorine. Having higher CYA allows it to bind with the produced chlorine to reduce the buildup of disinfecting chlorine to keep the SWG efficiency high.

 

[cliff_s]

I am skeptical that this is actually true that CYA increases the cell efficiency. What you are seeing is
the lengthening of the time of dissipation of the chlorine. As the CYA levels are increased there is
more residual chlorine left at the end of the day which adds to the next days residual level. This
looks as though the Cell has generated more chlorine, but in fact it has not.

The chlorine is formed as very small bubbles on the plates of the cell and then are literally blown off
the plate by the velocity of the water. The CYA might slightly lower the waters resistance thus making
a slightly increased amount of current to flow through the cell. Since most SWG's use regulated power
supplies this small change in resistance will make no difference in the current flow. The amount of
chlorine generated is a direct function of current flow, so unless the current flow is changed the
amount of chlorine generation remains the same.

Water temperature is the other variable, the higher the water temperature the faster the chlorine
dissipates. So the more chlorine that is needed to maintain any desired level. Then add the sun's
UV rays to this and again this increases the speed of the chlorine dissipation.

You need to have some residual chlorine available at the end of the day if you generate your chlorine
during the evening hours. An alternative is to add generating time during the day. It would seem as though
the most efficient would be to generate the chlorine during the day as it is used and keep the CYA as low as
possible. The only problem with this in most places there is a greater charge for electricity used during the
daylight hours. Since during darkness little chlorine is lost due to UV rays little chlroine would need to be generated.

Cliff s

 

[chem geek]

Cliff,

[EDIT] Sorry, I see I repeated myself, forgetting I posted here earlier. I do have additional info regarding evaporation vs breakdown from sunlight. [END-EDIT]

I started out thinking the same way you were, but with more and more SWG users reporting this dramatic increase, I'm leaning towards the cell efficiency explanation (and came up with a chemical basis for it including discovering that the rate constants nearly matched perfectly with what was needed to see dramatic improvements at around 50 ppm or so, though that is dependent on cell size and flow rate assumptions). Take a look at this graph that shows the chlorine half-life in direct noontime sun (directly overhead). Though more CYA does extend the half-life, it has a barely measurable effect after the first 20-30 ppm CYA. So to see such a dramatic change probably means something else is going on. It's true that in hot states some users report the chlorine lasting longer with more CYA, but it isn't as dramatic as this.

Unfortunately, the only way to prove this is to generate the chlorine at night, preferably with a cover on, and compare FC addition rates at different CYA levels. That would eliminate the sunlight breakdown of chlorine and evaporation issues.

By the way, the chlorine degrades during the day mostly due to breakdown from the UV rays of sunlight, not from evaporation (the hypochorous acid concentration at 3 ppm FC with 30 ppm CYA is 0.042 ppm or 42 ppb while the equilibrium concentration in air is 0.085 ppb or nearly 500 times smaller at 85F -- at 104F or hot tub temps the equilibrium concentration in air is roughly doubled so outgassing rates are at least doubled). The evaporation rate of chlorine is rather small except at higher temperatures and with lots of aeration. So in spas this is more common, but in pools it's not. At some point I'll calculate the maximum evaporation of chlorine from a pool from the SWG hydrogen gas bubbles (and the maximum carbon dioxide outgassing from that same process) assuming "perfect" aeration, but that's a project for another day.

Anyway, until the ultimate experiment is done, this issue will remain controversial.

Richard