Recommendations Based On Pool Water Analysis

[dvh]

Have a 40k gal inground chlorine pool and have run into a strange situation where I can't get the chemical levels in line. Decided to have a water analysis performed and came back as listed below. The company that did the analysis recommended draining the pool part way and refilling then bringing a new sample in. Before I do this wanted to hear thoughts from some of you on here... The strange thing we are seeing is the chlorine level test high and stays high, which we've never experienced before. Usually disipates very rapidly this time of year.

Test Results:

Free Chlorine: 5.4ppm

Total Chlorine: 5.4ppm

Combined Chloring: 0.00

PH 7.7

Hardness: 400ppm

Alkalinity: 73ppm

Cyanuric Acid: 125ppm

[chem geek]

This is just baloney and you should link to attributions when you are quoting someone else (i.e. this link). It has been known science since at least 1974 what CYA does to chlorine and how it works. TDS has nothing to do with it. Saltwater pools (with 3000 ppm salt and around 3200 ppm TDS) have no more problem with algae than lower salt pools -- high salt = higher TDS. The idea from the link about what Jonas presumably said is laughable -- TDS interfering with chlorine's ability to get around the pool. Chemistry doesn't work like that. After all, water molecules are in the pool at far higher concentration yet why don't they "interfere" with chlorine's ability to move around the pool? Unbelievable the kind of junk that people totally and completely make up. If Nat Jonas (is this they guy that founded N. Jonas & Co.?) actually said that, then if he's a chemist he's not a very good one. According to this link, Nat Jonas put together a team of chemists and researchers to make pool chemical products, but it doesn't sound like he was a chemist himself.

Now it is true that higher CYA levels will reduce the rate of chlorine loss from the UV in sunlight and that is what you are seeing. At a CYA of 100 ppm, the loss rate is around 15% per day (depending on the intensity of sunlight which depends on the time of year and your latitude) so with your somewhat higher CYA level the chlorine loss would be even less.

The 1974 scientific paper that determined the equilibrium constants between chlorine bound to CYA and the active chlorine (hypochlorous acid, HOCl) that is unbound is in this link. There are tens of thousands of pool owners on multiple forums who have validated that the chlorine/CYA relationship is absolutely real and that at higher CYA levels you need proportionately higher FC levels to prevent algae growth. Now it is true that the chlorine bound to CYA has a small effect on pathogens so probably on algae as well, but it's about 150-200 times less strong than HOCl. At any rate, having 5-6 ppm FC with 125 ppm CYA is not that far off from what is needed to prevent algae growth if you are lucky that your pool is not high in algae nutrients (phosphates and nitrates). The unbound chlorine level is around 0.02 ppm while the effectiveness of the chlorine bound to CYA is around 0.03 at best, so this combo is roughly equivalent to having an FC that is around 5% of the CYA level if the CYA level were lower.

If I were you, I'd lower your CYA level at least down to 80 ppm so that you'd only need to maintain a minimum of 6 ppm FC if manually dosing (or 4 ppm FC if using a saltwater chlorine generator) while still not having too much chlorine loss -- perhaps around 20% per day so about 1.2 ppm FC per day.

[waterbear]

Have a 40k gal inground chlorine pool and have run into a strange situation where I can't get the chemical levels in line. Decided to have a water analysis performed and came back as listed below. The company that did the analysis recommended draining the pool part way and refilling then bringing a new sample in. Before I do this wanted to hear thoughts from some of you on here... The strange thing we are seeing is the chlorine level test high and stays high, which we've never experienced before. Usually disipates very rapidly this time of year.

Test Results:

Free Chlorine: 5.4ppm

Total Chlorine: 5.4ppm

Combined Chloring: 0.00

PH 7.7

Hardness: 400ppm

Alkalinity: 73ppm

Cyanuric Acid: 125ppm

I assume that you do not test your own water so you don't know what is going on in your pool. This is your first problem. You don't have a clue what is going on in your water. The reason that your chlorine levels staying high is because the high stabilizer levels. Period. The downside is while the chlorine level stays high it is mostly in the form of chlorinated isocyanurates, which do not have the same activity as hypoclorous acid (Free Chorine).

As for your reference to N. Jonas in the posts that were hidden because of your insults to another member, realize that his company sells a LOT of stabilized chlorine products so it is in his best interest to promote the myth that high CYA is not a problem but high TDS is. (Also since he died in 1995 the usual corporate line from all the companies pushing chorinated isocyanurate products was that CYA did not matter. Much has changed in the past17 years !) This is just plain rubbish and goes against all that is known about the chemistry of chlorinated isocyanurates.High TDS in and of itself is not a problem, However,there are certain ionic species that contribute to TDS that are. For example salt is not a problem (sodium and chloride) nor is lithium. Calcium can be if it is a major component of the TDS as can sulfate (from non chlorine shock and dry acid use) but the main component of TDS that will interfere with chlorine activity is the cyanurate ion. When there is a high concentration of this (such as evidenced by having an cyanuric acid level of 125 ppm such as you have) then their is a major problem.

i don't claim to be a pool wizard--not my expertise.

In that case, instead of insulting and contradicting one of our most knowledgeable contributors in the area of pool water chemistry perhaps you would be better off listening to what he has to say and applying that to your own pool.