Converting to salt...part II

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300winmag

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Aug 2, 2016
214
Dallas, TX
My PB has set my SWG to 50%, with a pump run time of 15hrs / day. I'm now on my own :)

I measured my FC immediately after he changed the settings on the controller, and got a reading of zero (lots of rain, followed by lots of sun). With that said, will my Jandy 1400 SWG generate enough chlorine at the settings mentioned above to achieve the desired value of 4?
The unit can produce 1.25lb / 24 hrs, so at 15hrs I should make .78125lbs. How many ppm does .78125lbs into 16,000 gallons yield?

Once I know that, I can adjust the SWG % up (not enough FC) or the % / pump run time down (too much FC). Of course, I will also manually test it each day for a week, making sure that I get it dialed in.

Thanks
 
That's 12.5 oz of Cl2 gas. If you put that into the effects of adding chemicals section of Pool Math with your proper pool volume at top, you get 5.9ppm FC.

You should set your FC level using liquid chlorine (bleach) and then let the SWG run from there. SWG's can not bring up FC fast enough and you'll get in trouble if you leave the FC that low for too long. Also, should you ever notice your FC production falling even though the % output increases, it's a good bet you have algae growing. SWG's can not fight an algae bloom, only liquid bleach and a SLAM can do that.

Get bleach in that pool NOW.
 
Also, a clean and clear swimming pool with no algae load and typical bather loads will consume anywhere from 2 to 4ppm of FC per day. So, you should target your SWG % output and pump run times to produce enough FC to match the loss rate of your pool. If you maintain a high enough CYA (70ppm is really the minimum for most SWG pools in hot & bright climates), then your loss rate will be lower and your SWG/pump run times will be minimized. I keep my pool at 80ppm CYA (and I've toyed with going higher to 90ppm) and my loss rates are very low. I only have to run my SWG 5 hours per day at 50% to hold my pool FC levels steady and maintain a clean pool. Your mileage may vary....
 
The process of dialing in takes time and lots of measurements. Leave it where it is now and see where your FC is tomorrow. If you're above your target, then I would suggest cutting back pump run time as that will be largest power draw. In fact, you are better off running your SWG at a higher % output and lowering pump run time to optimize power consumption. You have a high quality SWG that knows to reverse polarity every few hours; they can be run at high % output without any detriment.

As for chemical balance, you need to start posting full sets of water results including calcium hardness (CH). Since you have an SWG, you will need to track your CSI (calcite saturation index) value closely. You want to maintain a slightly negative CSI value (somewhere between 0 and -0.1 is a good place to be but you can go all the way to -0.3 without any issues). This will mean finding a mix of pH and TA that keeps you CSI low (CH rarely changes unless there are extreme water exchange events). As I said previously, you will want to keep your CYA on the high side once you are sure everything is ok with your water (you may want to start tracking overnight chlorine loss with no SWG running to ensure your OCL is less than 1ppm). High CYA let's an SWG run less which saves cell life.

Please start frequently testing and posting test results.
 
This is the first I'm hearing of CSI; how is it tested? Or is it a calculation based on other results?

Per Pool Math, I added all chemicals (less bleach) after the PB left to hit my targets: CYA 75, pH 7.7, TA 70, CH 400.
Now that bleach was added, I'll let it all circulate until tomorrow and retest in the AM, afternoon and evening to see where I'm at. I'll post all my results in this thread.

Thanks again!
 
Read this - Pool School - Calcium Scaling

If you want to read a very technical discussion of the topic, see here - Calcite Saturation vs. Calcium Level for Plaster Protection

CSI is calculated by Pool Math when you enter in all of your water test results. With your current test results and a water temp of 88F, your CSI is -0.04. That's ok. CSI is important for SWG's because the pH inside the cell when it is running is extremely high; it can be on the order of 10.5 or more. Because of the extremely high pH inside the cell, the cell plates can scale with calcium carbonate and then the effective area for chlorine generation is lower. Once plates start to become covered in scale, the SWG will start reporting low salt because it thinks that there is not enough salt in the water when, in fact, it's just a decrease in current density due to a lower effective area. Many new SWG owners will often make the mistake of adding salt to correct the problem and then not realize that it is calcium scale causing the problem. Then, when they finally figure it out, they now have pool water with a salinity well above the required amount.
 
Thanks for the info! I'll keep an eye on it too.
FYI, water temp is only 83. Been unseasonably cool here ;)

my PB said to acid wash (3 parts water, 1 part muriatic acid) the SWG plates every three months. That sound like good advice? Too frequent, not enough?
 
300winmag said:
Thanks for the info! I'll keep an eye on it too.
FYI, water temp is only 83. Been unseasonably cool here ;)

my PB said to acid wash (3 parts water, 1 part muriatic acid) the SWG plates every three months. That sound like good advice? Too frequent, not enough?
Click to expand...

Wow! That is totally BAD advice.

First of all, you only clean the plates when they have obvious scale on them. You can pull the cell and visually inspect that frequently, but if you need to acid wash them like that every time, then your water is out of balance. I have had my cell running for over three years now and I have never had to acid clean it...not once.

Second, that ratio of acid to water is way too high! 5:1 is more than you would ever need to expose the plates to and, even then, that is extremely harsh. The SWG plates are titanium coated with a mixture of transition metal oxides (ruthenium, rhodium, platinum) to help generate the chlorine gas efficiently. That catalyst layer on the titanium plates is very susceptible to acid attack and, each time you acid clean the plates, you remove some of that coating. When that coating wears down, the cell plate efficiency drops and, if the coating fails, your cell is done.

So, your goal is to never have to clean your plates. You do that by maintaining a negative CSI and avoiding calcium scale in the first place.
 

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JoyfulNoise said:
So, your goal is to never have to clean your plates. You do that by maintaining a negative CSI and avoiding calcium scale in the first place.
Click to expand...

I wish I lived in your world, Even though my csi is always negative I still get scaling in the swg, evident by the white flakes emitted when it self cleans. I think from another thread that JoyfulNoise has borates added?? that may help with the scaling.
 
bobby1017 said:
I wish I lived in your world, Even though my csi is always negative I still get scaling in the swg, evident by the white flakes emitted when it self cleans. I think from another thread that JoyfulNoise has borates added?? that may help with the scaling.
Click to expand...

I ran my SWG pool for over a year before I added borates and I still had no scale. Granted my CH was lower back then, probably around 450ppm or so before I added borates (but I'd have to check my notebook to see what the CH actually was).

Adding borates can be very helpful in alleviating calcium scale in a cell because the pKa of the boric acid/borate system is ~9.0 (depends on salinity levels). Since the borates strongly buffer against pH rise inside the cell (cutting it down by about half or so), it lowers the CSI inside the cell. But that is not the whole story. I also keep my CYA at higher levels (as well as my phosphates now at low levels) which reduces my daily chlorine loss to very low values. I only have to run my SWG for 5 hours per day at 50% output (so effectively running my cell for 2.5hrs/day) in order to maintain the chlorine levels I need. I could increase my SWG output and save on energy costs by running my pump less BUT I like to keep my pool very clean so I maintain a 5 hour pump runtime per day so the cleaner can run (as well as my water features). Because my SWG doesn't have to run a lot and because the borates really keep my pH in check, my cell never really develops any scale. This is also another good reason to always get the largest SWG cell you can afford - the goal is to run them as little as possible and maximize their lifespan.
 
just tested the water:

FC: .3
pH: 7.7
TA: 90
CH: 350
CYA 45
Salt: 3200

How can my FC be .3?! I added 95oz of bleach earlier, and the SWG should have been running all day. I presume that I should add more bleach?
How do I lower TA? Add acid, and aerate, then repeat?
 
Your CYA is kind of low for your climate. BUT, you could have algae starting because your FC was too low.

You need to do an overnight chlorine loss test. When the sun goes down you need to raise your FC up above 5ppm, get an exact reading of the FC before bedtime (it's ok if it's over 5ppm) and then measure again before sunrise (try to get 8 hours if you can). No SWG should be running during this time period. If your FC loss overnight with no sun is greater than 1ppm, you'll need to SLAM your pool.
 
Should I add chems to increase CYA, or leave that be for now?
The sun is just about down; I'll add bleach now (111 fluid ounces). I'll also shut off the SWG.

Should the filter pump run overnight? It is scheduled to shut off at 10pm (2.5hrs from now).

SLAM means what? I have not seen an article specifically on it, but I take it as adding bleach to a certain FC level?
 
OK, no CYA will be added.

Pumps on or off overnight?

Assuming I loose more than 1ppm over night of FC, per the chart in the article you linked the FC target only goes down to CYA of 60. What should I use for 45?
Thanks!!


I'm off to buy some more bleach
 
Pumps on, SWG off.

Use the manual bleach chlorination chart (act like you don't have an SWG). Don't buy too much bleach. Let's just see where you're at. If you have to SLAM, we may want to use a lower level of FC.

How new is your plaster??
 
OK, pump will be on continuously, and SWG is off.

Plaster was completed and water-add began on 27 JUL. The pool was full on 28 JUL. Salt was added yesterday, and SWG turned on today. The PB might have treated the water 4 times since it was initially filled; certainly no special treatment / shock at start up :(

I got plenty of bleach...but can return what I don't need.


I'll test FC at 9pm, and again at 6am.
 
Almost two full gallons of 8.25% bleach went in tonight, and the highest FC I got was 1.5.

6:30pm; almost a gallon was added (111 fl. oz), per the pool calculator.
8:00pm; tested water and FC was 1.0.
8:30pm; added one full gallon, trying to get FC to ~5.
9:00pm; tested water and FC was 1.5.
9:25pm; tested water and FC was ~1.5 again. I'll post a picture of the two different test kit results for this reading shortly.

 

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