Low Salt Aqua Rite Generator

[RandB]

The TFP guidelines for maintaining a SWCG are not working out that well for me. I installed a low salt version of the Hayward Aqua Rite (Canada version) about 9 months ago. Things were looking very good until I raised the CYA concentration from 65 to 80ppm. I run the system daily at low rpm for 8 hours at 42%. After several weeks, the water seemed to be getting cloudier; however, this is a time of lots of Saharan dust and local wind-blown dirt.
I assumed that my slightly cloudy water was merely fine suspended dirt as my CC was 0.5 and I kept my FC to 6ppm.

For another reason I had to lower the pool water by half and after refilling I did not replenish the CYA which now stands at 35ppm. I added too much supplemental liquid chlorine to 18 ppm (forgetting the CYA was now low)….suddenly the water is crystal clear, glassy and vibrant. I kept the chlorine at 18 ppm for a few days then stabilized to 4 ppm. The water has remained perfect now for the past 4 weeks.

My clarity problem could still have been dirt, but I am thinking now that perhaps it was organic. Although the CC was 0.5, the pool consumed 2-3 ppm chlorine overnight the first night. Now the pool is staying sparkling clear despite dirt accumulating on the bottom. The pool is now consuming < 1 ppm chlorine overnight and CC of <0.5.

The only other difference I can identify is a backwash before lowering the pool level.

So, my question….could it be that using a low concentration of 1,200 ppm salt (hence producing less chlorine per unit time within the cell), that perhaps this is not sufficient to fully treat the water as it passes through the cell? Hence, using the TFP recommended CYA level of 70-80 is too high in this type of set up? The manual for the chlorinator specifies a CYA at 30.

I appreciate your advice…

Current status (Taylor Kit K2006):
FC = 4.0
CC = <0.5
pH = 7.7
Alk = 70
Ca = 80
CYA = 35
Water temp. 82-84°F (day and night, all year)

 

[ajw22]

So, my question….could it be that using a low concentration of 1,200 ppm salt (hence producing less chlorine per unit time within the cell), that perhaps this is not sufficient to fully treat the water as it passes through the cell? Hence, using the TFP recommended CYA level of 70-80 is too high in this type of set up? The manual for the chlorinator specifies a CYA at 30.

No.

The water is not "treated" as it passes through the cell. Chlorine is generated which flows to your pool and mixes with your pool water.

1200 ppm is low for your cell. 1500 ppm is the optimal salt level. Are you measuring the salt level with the K-1766 Taylor Salt Test ?

I think your water got some algae and needs a big does of chlorine to clear it. Next time fo a Overnight Chlorine Loss Test when you see that problem developing.

 

[RandB]

Yes, thank you for the response. I guess I mis-understood. I was under the impression that the 'rationale' for using very high levels of CYA in salt water chlorine generator pools, compared to manually dosed pools, was that the thinking is as the water passed through the cell is was exposed to very high levels of chlorine. If it is simply that the water is chlorinated to keep the pool chlorine at the desired level, then the ratio of CYA to chlorine is not consistent with the recommendations for a manually dosed chlorine pool and they should be the same.

I believe I quote Richard Falk, "The chlorine level near the chlorine generation plate in the SWG is very high....and also at a low pH so it's definitely super-chlorinating the water in that area." ..."This might be killing enough free-floating algae to allow for a lower FC/CYA ratio in SWG pools". If the later is true for typical SWGs, then a low-salt generator is producing less 'super-chlorination' in the area of the cell(?), and hence my confusion.

While the optimum for this low-salt cell is 1500 as you say, the recommended range is down to 1200. Mine is usually between 1300-1400. So far my CYA of 35 is working and I don't have much of a problem with my pH rising. It is almost always between 7.7-7.9. I am hesitant to raise my CYA level again to the recommended level.

Thank you.

Regards,
Richard

 

[ajw22]

SWG chlorine output is proportional to the salt level. Running your salt at 1200 gives you about 20% less chlorine generated then if your salt level was at 1500. You can run it at anywhere you like, just understand you are not generating the optimum amount of chlorine the cell can produce.

The lower FC/CYA ratio for the SWG is due to the SWG being able to maintain a more consistent FC level when the pump is run all day and the FC is being constantly replenished against the CL lost to UV.

You need to subscribe to the turnover myth to believe that all the pool water needs to flow through the SWG while it is operating every day for the "super chlorination" to sanitize the water. That is not what happens to keep the water sanitary. Lots of the water does not flow through the SWG in a day yet it remains sanitary. And The chlorine needs to sanitize the water while it is in the pool. So what you quote is an interesting bit of trivia but not how things really work.

If CYA 40 is working for you then it is fine. You are just giving up CL to the suns UV unnecessarily. With your small pool and SWG capacity it does not make a big difference.

BTW, we round CYA levels up. CYA 35 is meaningless as the scale of the CYA lines is logarithmic, not linear. You can't eyeball values between the lines. So if the dot disappears between 40 and 30 we round up and call it 40.

 

[RandB]

Yes, I understand, thank you. But 1200-1400 produces plenty of chlorine for such a small pool. I don’t know what “optimum amount of chlorine” means. I believe there is nothing special per se about the cell itself, it is a T-Cell-15 I was told. If that is true, then the target ‘optimal’ salt level would be 3200 and at that level producing likely more than twice the chlorine. The point is the desire for a low salt experience, we love it between 1200-1400…at 1500 or more in not as pleasant.

Your comment concerning the lower FC/CYA ratio, is at odds with the statement from Richard Falk, that you call a ‘myth and a bit of trivia’. I did not understand from his comment that he was in any way suggesting that “all of the pool water” need to flow through the cell to be effective. Of course, the chlorine level is maintained in the pool to provide sanitation. The conundrum he was trying to address is the relative chlorine effectiveness at 80ppm CYA.

If I understand you correctly, the cell is simply producing chlorine that maintains the level of chlorine similar to adding liquid chlorine. Yet, this description does not provide an explanation for the basis of the TFP official Recommendations significant difference between SWCG pools and liquid chlorine-dosed pools for the amount of CYA. This is not about what I do. As you say I can do whatever, it is about the TFP recommendations.

I remain confused about the TFP recommendations for SWCG pool. Based upon your view there should logically not be any difference in recommendations. That seems exactly consistent with my experience to date (with a low-salt chlorine generator); hence, my initial query.

I followed the TFP recommendations and it did not work. That could be for a whole host of other reasons, but I thought if Richard Falk’s ideas were at all correct, then those using low-salt systems might need a modified recommendation.

Thank you again for the discussion, perspectives and contributions.

Richard