Ideal Salt Level Pool Pilot

[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).

[smallpooldad]

Waterbear,

ORP at 700 is approximately FC of 6.

At night as the sun sets ORP might get to 725, but only if I run the pool into the night say 10 pm to 11pm if my children are having a party and I set it higher say at 775 will it ever reach 750.

The main issue I believe is that we live up at about a 1000 ft and trade winds averaging 16 to 24 mph blow very fine dirt into the pool. So 800 will never happen unless I run it 24/7 and we do not have the money for that. Trade Winds are an issue for most pools in Hawaii, I love the trade winds it keeps us cool on hot days but they do blow around a lot of dirt.

I would really like to get one of those low pressure pumps that one can run 24/7 that uses only a little electrical current but sadly they are only manufactured for 2" lines.

So FC of 6 it is. The pool is brushed daily so there is no algae of any kind present at this time that we are aware of.

Thank you for your help.

[smallpooldad]

Waterbear,

I did a little further research.

While ORP values are useful values for predicting algae breakouts in aquariums the ORP value for aquariums do not translate to pools, as marine aquariumss are controlled environments (where the temperature, UV, are constant and wind normally plays no part) albeit that higher values can guarantee higher FC chlorine levels. Predicting algae breakouts in pools using marine aquarium guidelines would normally not be of value as other levels such as ammonia, nitrates, nitrites, phosporous, and especially the fact the salt ppm (normally 30,000 to 50,000 ppm) in marine aquariums is many times greater than in a pool. Additionaly chlorine is normally not used in salt water aquariums but Nitrifying bacteria are used, this is not so in salt water pools, see here:

http://en.wikipedia.org/wiki/Aquarium

It seems that two pools with identical ORP values can have different levels of FC, and even these ORP values can fluctuate quite a bit depending on the time of day.

For example an ORP value of 700 in one pool may indicate an FC of 6, while and ORP value of 650 in another may also indicate a FC of 6. Even the same pool can have wildly swinging ORP numbers in the course of one day but still have FC readings of 6 consistently throughout the day.

Obviously as with aquariums the larger the size the less the fluctuation, a 50 gallon tank will fluctuate more than a 500 gallon tank, so it seems this is also true of pools.

I believe that in a post from Chem Geek he stated that ORP value was not as valuable to pool chemistry as once thought and that the HOCL % was a better indicator as far as algae control was concerned. At least that is the way I understood his post. And from practical experience I would have to agree.

The time line of bacterial cross infection between humans is affected by ORP but at levels of 650 or 700 depending on your view, or 750 in a public pool, this is not a concern; at least in regards to algae control. 650 ORP is the current standard for most US public pools, Germany's is 750 but that as you know is extremely hard to achieve without very sophisticated equipment, which most US public pool do not have at present.

Additionally most persons do not have ORP controllers or complicated ozone setups to mitigate the loss of chlorine so for the average person HOCL% would most probably be an easier number to strive for as it can be easily calculated using CyA, pH, and the FC numbers.

It seems therefore that for those with no algae problems a SWG pool would be optimized at pH 7.5, CyA 35, and FC of 4, this gives an approximate HOCL % of 0.050 %, which could be considered a minimum standard. For those with algae issues the FC is better kept at 6, an HOCL % of 0.080%. Obviously if one raises the CyA ppm then one would have to either lower the pH (harder on the eyes while swimming) or raise the FC which most SWG are unable to do as they struggle at FCs of 5 or 6, unless they are oversized.

Any thoughts?

[waterbear]

The only reason I brought up the algae growth in aquariums is because ORP is a good indicator of the type of algae growth and if you are getting black algae then your ORP is too low. There really is NO direct correlation between FC and ORP. It is apples and oranges. 650 MV is the minimum recommend ORP for pools with 850 mv usually the recommended high end. My point is if you ar getting black algae then your ORP is too low.
I agree with Richard that ORP is not as valuable as FC levels in predicting whether a pool will have algae outbreaks or not but for an automated system it's what we have (unless you want to spend the money on a direct reading chlorine probe and controller!)

You are in error about lowering the pH to raise the HOCL levels when there is CYA present. Once CYA is present in the water the effects of pH on HOCL/OCl- concentrations goes pretty much out the window.

If the SWG is using ORP control then you have a problem raising the FC unless the unit is oversized, However, when CYA levels are higher then there is much protection from breakdown, not only by the formation of chlorinated isocyanuates but also by physical protection of the deeper. levels of water from the CYA which does act as a 'sunscreen' in this respect so chlorine loss from sun can be minimized even more. Richard has been commenting on this in many of his posts at troublefreepool.com


In actual practice it has been found that most SWG pools without ORP controllers do best at a CYA of 70-80 ppm (or even up to 100 ppm in places like Arizona -- and possibly Hawaii), a FC of 3-5 ppm, and pH kept between 7.6-7.8 with a TA of 60-80 ppm and CH dependant on pool surface with a plaster surface around 350 ppm CH to maintain the CSI.

IMHO, ORP complicates a salt pool. While it is useful in automating a commercial pool, whose chlorine demand can fluctuate greatly throughout the day (and I know a bit about this since I do maintain 2 large commercial pools, 2 spas, and a splash zone at a resort condo), it really is overkill on a residential pool and I feel it makes maintenance much more complicated.

[smallpooldad]

Thank you for your reply.

My apologies I made an error in the last posts HOCL % should be read as HOCL ppm.

Does this mean that the calculations in the "PoolEquations" spreadsheet are incorrect?

Using the numbers you mentioned above it seems that the HOCL ppm comes out in orange as 0.021, and the CSI comes out also in orange as 0.46. Orange I believe is cautionary, in that the HOCL ppm is too low, and the CSI is too high which is potentially damaging to the plaster. Please excuse me if I am reading these numbers incorrectly.

Here are the "PoolEquations" numbers.

Measured pH 7.7
Total Alkalinity (ppm CaCO3) 60
Free Chlorine (ppm Cl2) 4.0
Cyanuric Acid (ppm CYA) 70
Calcium Hardness (ppm CaCO3) 350
Total Dissolved Solids (ppm) 3,913
Total Sulfate (ppm SO42-) 0
Total Borate (ppm Boron) 50.0
Total Ammonia (ppm Nitrogen) 0.0
U.S. Gallons 10,000
Temperature (oF) 83

Total Chloride (ppm NaCl) 3500
Carbonate Alkalinity (ppm CaCO3)25.9
Langelier Saturation Index (LSI)-0.33 (shows as red danger too high)
% HOCl (vs. Total Free Chlorine)0.5%
OCl- (as ppm Cl2) 0.042
HOCl (as ppm Cl2) 0.021 (shows as orange cautionary too low)
Calcite Saturation Level (CSL) 0.35
Calcite Saturation Index (CSI) -0.46 (shows as orange cautionary too low)

If one uses the numbers that I calculated then the numbers come out within range and show no cautionary orange but a good green:

Measured pH 7.5
Total Alkalinity (ppm CaCO3) 80
Free Chlorine (ppm Cl2) 6.0
Cyanuric Acid (ppm CYA) 35
Calcium Hardness (ppm CaCO3) 425
Total Dissolved Solids (ppm) 3,933
Total Sulfate (ppm SO42-) 0
Total Borate (ppm Boron) 50.0
Total Ammonia (ppm Nitrogen) 0.0
U.S. Gallons 10,000
Temperature (oF) 83

Total Chloride (ppm NaCl) 3501
Carbonate Alkalinity (ppm CaCO3)61.8
Langelier Saturation Index (LSI)-0.07
% HOCl (vs. Total Free Chlorine)1.3%
OCl- (as ppm Cl2) 0.100
HOCl (as ppm Cl2) 0.080
Calcite Saturation Level (CSL) 0.63
Calcite Saturation Index (CSI) -0.20

If one changes my CYA number only, which you state has no effect on the HOCL relationships, then the numbers look like this. It clearly shows a relationship. Either the spreadsheet is wrong and needs to be modified or your statment might be incorrect. I wish Richard would clear this up for us.

Here are the numbers with CyA adjusted:

Measured pH 7.5
Total Alkalinity (ppm CaCO3) 80
Free Chlorine (ppm Cl2) 6.0
Cyanuric Acid (ppm CYA) 70
Calcium Hardness (ppm CaCO3) 425
Total Dissolved Solids (ppm) 3,933
Total Sulfate (ppm SO42-) 0
Total Borate (ppm Boron) 50.0
Total Ammonia (ppm Nitrogen) 0.0
U.S. Gallons 10,000
Temperature (oF) 83

Total Chloride (ppm NaCl) 3481
Carbonate Alkalinity (ppm CaCO3)50.4
Langelier Saturation Index (LSI)-0.15
% HOCl (vs. Total Free Chlorine)0.6%
OCl- (as ppm Cl2) 0.044
HOCl (as ppm Cl2) 0.035 (reads cautionary orange i.e. too low)
Calcite Saturation Level (CSL) 0.51
Calcite Saturation Index (CSI) -0.29

Even though it seems from some real live experiences of some, but not all, members of this forum (although not proven) that the CYA protects deeper levels the FC is still too low in relation to the HOCL ppm when calculated. My pool is ranges from 4 ft to 4 1/2 ft deep so depth is not an issue for me.

I would agree as I stated above that ORP complicates the issue as it seems to me that, once set, it only stops the further production of chlorine. Although that is a benefit. And I agree, as stated in my previous post there seems little relationship between ORP and FC. "NO" relationship I am not sure I could not be that definitive as I am neither a chemist, physics major, nor biochemist.

As regards Hawaii and Arizona I think there is difference, we are very close to the ocean, in my case just 1 1/2 miles, Arizona is far. Hawaii is humid most of the time Arizona is dry most of the time, although I have been there when it was very humid. In Hawaii mold grows even on the sidewalks, in Arizona I believe this is not so. Sea going algae must be carried in by the winds here, normally 16 mph to 24 mph. It is unlikely that sea going algae blows into Arizona from the Pacific, although a little might make it.

The black algae here seems to be of a more virulent strain than that which grows in most parts of the mainland.

From my real life experience and that of my friend a FC of 4, pH of 7.6 or above, and a CyA of 70 guarantees one black algae at least where we live, especially in our old plaster pools.

At the present time I think we both beg to differ with each other. As I wrote above it would be good if chem geek could step in and discuss the spreadsheet as this seems to be the area where we disagree. It is entirely possible that it cannot allow for the effect of CyA in a salt water system. If this is so maybe a separate spreadsheet need to be written for salt water pools.

Please bear in mind my pool is 12 years old and while it has virtually no de-lamination it is old, my friends is severly de-laminated and is 17 years old.

At present I will stick with my system as it works for me in Hawaii.

It is entirely possible that we are both right, in our own ways.

One question I do have is, do you not like the pool setup numbers I use, they do not seem to be detrimental in any way? They are admittedly very cautionary.

Lastly as this is getting technical the moderator might wish to move us to the "China Shop". That would be fine by me but it is up to the moderator.

[waterbear]

realize that the CSI is just a guide and that a range of values is accdptable. Also, running a salt pool on the slightly agressive side is probably a good idea since it will help prevent cell scaling. Too much stock is put into saturation indecies. They are only guides yet the are treated like religions! In terms of agressive vs scaling water pH is the primary factor to look at. Since SWGs do cause a pH rise the numbers I gave include a 'saftety factor' for the inevitable pH rise that will occur.
I've said it to you before and I will say it again, you are overthinking things and making them more comlicated than they need to be. You also don't have as good an understanding of pool chemistry as you think you do as evidenced by your post on Omni's granular triclor. You have latched on to Richard's spreadsheet as if it were handed down on the mount from a burning bush. Remember, it is stricty theorectical and Richard and I have discussed theorectical vs real world results in depth on numerous occasions. I am not discounting it's usefulness BUT other factors do come into play so it should merely be a guide, not a rigid set of rules for pool care.

You said :
"From my real life experience and that of my friend a FC of 4, pH of 7.6 or above, and a CyA of 70 guarantees one black algae at least where we live, especially in our old plaster pools."

Was this with a SWG or was the pool manually chlornated and if so, how? It does make a difference.

[smallpooldad]

Waterbear,

I am sorry you seem to be upset. Forums are places where people can air their views, ask questions, and question the speakers, and their responses. I am merely questioning your responses. It is for the other persons reading it to decide what to do.

It is true that I use the spreadsheet as a guide as I believe professionals with college degrees in their respective fields know a lot more than I do and respect their opinion, or in this case their spreadsheet until proven wrong. I do realize that all cannot be held as gospel but your numbers just seem off the mark for me personally.

For this reason I usually follow the manual for my car when setting spark plug gaps and not advice from my local mechanic. He, the mechanic is very nice but not knowledgable about everything, he is convinced that setting a tire speced for 30 at 40 is good in Hawaii because it is hotter here, the tires stay cooler. My ex-brother in law, a former Formula 2 racing champion for many years and a degree in engineering related to autos and engines, told me that that is plain dangerous as it can cause planning on newly wet roads. The tire and car company agreed, as did his other racing buddies. But he did say to bump up 3 from practical experience.

Chem Geek so far has not steered me wrong for that reason I have learnt to trust him. Your specs seem, at least to me, to be a little too wide and general for my taste, others may accept these wider ranges, and indeed it may work for them, as it does for you, but I cannot. I prefer precision, that is just me, it does not mean I am right. Even at a pH of 7.9 allowing latitude to your numbers they still fall short on the spreadsheet. And my real life experience in Hawaii is different from yours in Arizona.

Mentioning my post on Omni's new product "Super Algae Destroyer" was below the belt. I believe there is no question that is too stupid to ask.

While on the same subject I was aware from having "Googled" it prior to the post that it was the same material as Trichlor but was interested to see if I was missing anything, I like to be exact and realize I do not know everything. Also I was hoping that others might learn from this post as so many newbies are naive. See here:

http://en.wikipedia.org/wiki/Symclosene

As regards CSI I think as I said I will steer to the side of safety as I do with HOCL ppm, why drive at 100 mph when you can drive at 30 mph and get their at the same time, and have a wider margin of speed.

"You also don't have as good an understanding of pool chemistry as you think you do as evidenced by your post on Omni's granular triclor"

I have none, but then most people, maybe all (except chem geek), who help here do not either. From experience and study they, and maybe I, have built a small sufficient working knowledge to apply it to this very small area of science, of how to maintain a pool. Let's face it, it is not as if we are trying to cure a major disease.

My friends pool for info is a SWG pool.

Ever since I turned my guide into a "Religion" my pool looks fantastic.

Finally it seems that you take issue with the spreadsheet, well that is your opinion and I respect that. You could be right. I have read many of your kind replys on this forum, many of which I have found to be very informative. I especially like the one that discusses pump ratings. But this question was originally about Optimum Salt Levels and this is where we should both leave it for now, I hope you agree. Otherwise we both might become similar to the Dad in that very old cruel and unpleasant joke, "Daddy, Daddy I keep going round in circles" "Shut-up or I'll nail the other foot to the floor." Why do we not just agree to disagree as we are looking at it from two points of view.

To the forum moderator:

If you wish to delete all postings, except the first two, on this subject that would be ok by me, if its is ok by Waterbear. Then it might be a more pleasant post and yet remain informative.