Ideal Salt Level Pool Pilot

[smallpooldad]

What is the ideal level of salt ppm for the Pool Pilot? The manual states 2500 to 3500. Is 3000 the optimum for chlorine production?

What, if any, are the benefits or negatives of running it at either extreme, 2500-3500? I do realize that lower levels produce a less corrosive enviroment and higher more corrosive; theoretically one could use less calcium with the lower number. The second consideration is that bees are attracted to the pool when the salt level is higher. I am told but do not know if it is correct that bees are attracted to salt, from my experience this is true. I can only suppose that they use the salt, as do horses, as a salt lick. Are there any other considerations?

I love this unit, SC-60, it maintains 6 ppm of chlorine and holds it there most of the day in 10,000 gal pool running 4 hours per day at level 3. Level 2 produces around 4.5 ppm.

The reason we go to 6 ppm chlorine is to control mustard and black algae, creating an HOCL as ppm of 0.080 at a CYA of 35 and pH of 7.5.

Any help would be appreciated.

[Poolsean]

You're not going to have a problem lowering your FC to 3 - 4 ppm.
That's a different topic altogether.

To answer your question, the Pool Pilot will operate properly from 2500 ppm on up. 3000 ppm is better but higher is even better. It allows the power supply to run cooler (internal temperature-wise).

When you run lower than 2500 ppm, you reduce chlorine production and can get to the point of cell wear.
Running higher levels of salt doesn't generate more chlorine, but again, helps the Pool Pilot run cooler, which always helps electronics.

[smallpooldad]

Sean,

You are so fast.

Great informative reply, I wished they had mentioned that in the manual.

As regards Chlorine levels for my pool and my neighbours higher is definetly better.

Thank you this was very helpful.

Aloha

[waterbear]

You are running your CYA very low for a salt pool. Try raising it up to aobut 70 ppm. You will find that your pH becomes less likely to rise since you will be able to run at a lower power level/output percentage and you will also find that a FC level of about 4 ppm is more than enough to control ALL forms of algae.

[smallpooldad]

Waterbear,

Thank you for your kind help.

I would agree that on most parts of the mainland 4 ppm chlorine might be fine, although some on this forum have stated numbers between 4 and 6 work better for them. Being further south at a latitude of 21.18 (Miami is at 28.10) it seems as if our algae, especially black algae, is of a stronger type or is benefiting from the extra UV radiation.

As black algae can only be killed, or maybe only controlled from growing, by a residue sitting on it, unlike other floating types which get wacked by the SWG. The poolperson who installed the generator stated that SWG pools in Honolulu have a tendency to get black algae unless they keep the FC at 5-6.

There are many different types of Black Algae I could assume that our type could be called "The Hawaiian Super Black Algae"!!!

I am not sure all algae can be killed by FC of 4, the killing part is the HOCL % this percentage is a far more important number than FC and that is dependant on a combination of pH setting , the amount FC, and the level ppm of CYA. The only way I know how to calculate HOCL% is to use the "PoolEquations" Excel spreadsheet; so it is not very user friendly for the general public.

Even then we now know that some forms of life can live in impossible area such as deep sea trenches, sulfur springs, etc. The use of "ALL algae" might better replaced by "most known algae". Here is a link that explains the many species:

http://en.wikipedia.org/wiki/Blue-green_Algae

At 4 ppm it slowly starts to raise its ugly head; at 6 ppm there is no sign of it. My Pool Pilot is set to an ORP of 700, power level 3, which produces and maintains a reading of 6 ppm FC. It runs for 4 hours per day (electricity is .35c KwH) so the shorter the better. The pool is 10,000 gals and has a flow of 55 GPM, so the turn is 1.32. The SWG cell itself does not run 4 hours per day as often it has reached 700 ORP even before it starts up. The pool is covered so this helps, it also assists in keeping the pH at 7.5 with little acid usage which is automated. If the pool were uncovered it might use more acid.

The HOCL % therefore with a CyA of 35 ppm is 0.080% (chem geek states that an HOCL % over 0.075 kills most known marine varities). Raising the CyA would lower this HOCL %, as would lowering the FC below 6, which what we are most interested in acheiving as it seems at this level can only be reached by a combination of pH 7.5, CyA at 35, and FC of 6. If we raised the CyA level we would need to produce a higher chlorine level and that would require the SWG to run longer. The aforementioned combination of numbers seem to give the optimum results, the pH level of 7.5 is good for the eyes and the chlorine is still at safe levels. Pool Pilots Manual states this is OK so long as one is digitally automatically feeding the acid.

My friend's pool (20,000) gals runs for 8 hours per day. He has a Jandy Autopilot 1400, it is turned up to 81%, the pool is uncovered and his pH rises by about from 7.4 to 7.6 each day, he has, as is mine, an Alk of 80, he does not use borax, I do. His FC is maintained at 6, and again no black algae. We plan on automating his acid feed.

I believe there are no hard and fast rules but if you saw how fast mold grew in Hawaii I think it would be easier to understand. I think that latitude and humidity also play a part in what variety of algae one gets. Hope this explanation helps in understanding why we are so neurotic over FC levels.

Finally I have to admit to being a little confused as I am not a biologist or biochemist, maybe Chem Geek can clarify this, why does one have to shock a pool at say 25 ppm of chlorine if 4 or 6 ppm of chlorine (HOCL% dependant) is killing most known algae? What further benefit does the shock have? I realize that the levels do have to elevated somewhat as the chlorine is used up in destoying algae but by why so high at say 22, or 25, or 29 ppm?

[waterbear]

Ok, did not realize that you had a Total Control system. That's a different animal completely. As far as the level needed to keep away black algae it's not so much the FC as the ORP reading. 700 mv is on the low side of the usual range. In your climate I would think an orp reading closer to 800 mv would be better, particularly when trying to kill black algae (which is really a blue green algae or cyanobacteria) .
In marine aquairums ORP readings can accurately predict the type of algae that will grow. When the ORP is low you will get red and blue green algae (usually in that order). As ORP continues to rise (usually from the use of ozone or H2O2) then brown and finally green algae appear. This means that black algae is more likely to grow in less oxidative envionments than green algae. This is in line with what we know of black algae, that it grows under conditions of low chlorine (low oxidation potential) over an extended period of time. Another characteristic of black algae is that it has a heavy, gelatinous cell wall and it tends to grow in layers, one upon the other. Therefore, a first line of defense in killing is it frequent brushing with a wire algae bruse and using a combo wire/nylon brush for normal pool brushing (assumiong a plater pool---however black algae is not as extensive a problem in fiberglass and vinyl pools).