Dietitian

If this is true (which I'm not doubting) how come my water has remained crystal clear (with heavy tub use) for the better part of a couple months, despite having the rocket high CYA? What's more, no itching, rashes or biofilm? In otherwords, what signs wold there have been if my FC was indeed that much less than what you propose? I've only had the clouding issue when adding non chlorinated shock. THANKS! The water would have likely turned cloudy even if you had not used MPS. The cloudiness is probably a result of the chlorine concentration dropping low enough to allow something to grow in the tub and cloud the water. The MPS you add when you get home may not be enough to combat whatever your friend left in the tub, and the CYA is keeping the chlorine's power so low that the FC is having trouble oxidizing bather waste. I would drain the tub and begin using Nitro's method, making sure to keep CYA lower, around 30 ppm.

I don't have your spreadsheet, where can I find it? I am using 5*FC/CYA. I'm asking because I would like to set the chlorine to the max safe level before 5 people enter the spa, in order to keep active chlorine in the water as long as possible. With 5 people burning 7ppm/hr each, if I get the FC up to 24ppm before entering, we should be able to soak for 30 mins easily without losing all the FC.

Pool water or drinking water can cause dental corrosion if the pH is too low. Ca10(PO4)6(OH)2 + 8H+ --> 10Ca2+ + 6HPO42- + 2H2O Most I.V fluids are acidic at a pH from 3.5 to 6.2. Reference Pool water is maintained around PH 7.5, so it should be ideal for avoiding irritation to skin and eyes; and I would imagine that drinking water PH should ideally be similar to pool water. From the link about IV fluids: "The acidity of [i.V] fluids has been criticized for its corrosive effect on veins." It is acidic to keep the fluid stable in the bag, but it damages veins. The article about acidic pool water is amazing; the maintenance guy tested the water at PH "6.8" but that is the bottom of the range for the red phenol drop test, additionally, he failed to keep records of the testing, so he likely didn't do anything to the water at all (it had an automatic gas chlorination system), and it was allowed to reach a PH of 2.7!

I guess my method "Active oxygen" is lost in translation (swedish to english). Should work as an oxidizer but not disinfection, hence the chlorine that I add once a week (so far). I guess I will take the advice not to remove pillows. There are always replacements to buy.... /Z Perhaps you are referring to hydrogen peroxide as "active oxygen?" H2O2?

Your CYA level is too high, and most of your 3 ppm FC is bound to the CYA. You should have about 30ppm CYA in the tub. At current levels your effective "active" chlorine is about 0.12 ppm

Assuming I have 30ppm CYA in my spa, would the maximum safe chlorine level be ~24ppm? My calculations show that this would be about the same as having 4ppm non-stabilized chlorine in the tub, which is generally the highest recommended level for drinking water and pool water. Is this correct? Can I really use a spa with CYA 30ppm and FC 24ppm?

Yeah, it almost certainly has an infection if it has been sitting without maintenance for any length of time. Here is the product I used with success. Let us know if it works! http://www.amazon.com/Creative-Spastart-Sp...0696&sr=8-5

Excellent, thank you.

The World Health Org. standard is: Total dissolved solids (TDS): Min 100ppm, ideal is 200-400ppm PH (Acidity): As close to 7 (Neutral) as possible Calcium: Min 20ppm, ideal is 40-80ppm Magnesium: Min 10ppm, ideal is 20-30ppm http://www.who.int/water_sanitation_health...mineralized.pdf Their recommendation for PH 7 seems a little strange if our teeth begin to dissolve at 5.5, our tears are 7.5, and our blood is 7.4: "The mean pH values of 40 eyes from 20 healthy volunteers was 7.50 (SD +/- 0.23)" http://www.ncbi.nlm.nih.gov/pubmed/9154387 "the mean pH value for the six subjects [tears] was 7.50 ±0.16 (SD)" http://www.iovs.org/cgi/reprint/30/4/747.pdf "Blood pH is regulated to stay within the narrow range of 7.35 to 7.45" http://en.wikipedia.org/wiki/Blood#pH

You probably have a buildup of biofilm in the plumbing. I recently had the same problem and used "Spa Flush" for 30 mins, drained and refilled and the problem was gone. Shocking the spa with huge amounts of bromine won't (I used 100ppm chlorine and it still didn't work) break the biofilm barrier, but the Spa Flush product will be able to break the biofilm and destroy it.

Does chlorine reduce linearly or logarithmically? If it is linear, why do we measure chlorine demand in percentage terms instead of fixed, say "demand is 5ppm fc per 24 hours?"

Assuming you have a calcium hardness around 100, your water would be calcite saturation index balanced at about -0.16 CSI. If you bring the PH to 7.4 it would be 0.03, which is even better. My understanding is that a high TA isn't bad per se, but will make moving the PH harder when you want to adjust it (that's why you have to add so much acid to move the PH even a little). Put all your numbers in the pool calculator and see if your CSI is good. If so, and if your PH is stable over time, don't worry about the high TA.

You don't really need to go to 10ppm each week. As long as you add enough chlorine after each soak, the combined chlorine will be destroyed. Shocking is only needed as a "catch up" when not enough sanitizer was used in the past. Are you using CYA? I would perform a test of the spa's chlorine demand. Get the level up to 4ppm and soak for 15 minutes. Re-test the water and calculate how much chlorine was used during the soak, and the next time you soak you can use this number to estimate the demand of the tub after your next use, and add the correct amount of sanitizer. For example, if you re-test and find 2ppm chlorine, you will know that each person burns 1ppm chlorine every 15 minutes, or 8ppm for two people for an hour. After an hour soak, you would add 8ppm chlorine, after a half hour, 4ppm, etc. The rule of thumb around here is that a spa will use about 7ppm per person/hour, but that is the top of the range -- clean people who don't pee in the water should have a lower demand.

Ideally you don't want the PH going out of range, so you would balance the PH first, then add borates and acid in small amounts to keep the PH reasonable, then add chlorine and calcium. It probably isn't that important as long as you wait for each to reasonably dissolve before adding the next chemical, and the PH isn't out of range for more than a minute while you add chemicals. PS The pool calculator for the iPhone is highly recommended. If you don't have an iPhone you can use the same calculator online here: http://www.poolcalculator.com/

If you have a chlorine buffer in the spa (CYA, Cyanuric Acid, "Stabilizer") the active chlorine will be much lower, and will not impact the cover, pillows, or bathers as harshly as unstabilized chlorine. Recommended levels are ~30ppm CYA and ~4ppm free chlorine. At his level in a spa, the amount of "active" chlorine will be approx 5*FC/CYA, or 5*4=20 divided by 30 = 0.67ppm free "active" chlorine. CYA is effectively holding 3.33ppm chlorine in "reserve" by binding to it, and as the chlorine is reduced by bather waste/sunlight the CYA releases more active chlorine to fill the void, keeping the effective chlorine level at 0.67ppm until the entire 3.33ppm reserve is used up. Your pool store will likely tell you that using CYA in a spa isn't needed because it rarely sees sunlight, but the store is also likely unaware of the CYA/Chlorine relationship, first extensively studied in 1974.

Yeah I don't necessarily want to raise the PH of the water, but I was curious about how sensitive it would be to C02 loss.... Our blood, eyes, and mucus membranes are PH 7.4 as I understand it, so I would imagine that finding a water with PH 7.4 would be ideal, no?

It's unfortunate that plax doesn't work. Spa Flush worked very well on my spa (infected with something, huge CD). If it can remove the biofilms in my tub that easily, one would think that a similar product could be developed to remove the tooth biofilms that lead to decay. The stuff looks pretty harmless according to that data sheet, but I wouldn't put it in my mouth unless I knew exactly what was in it.

Why did you choose 12.5% chlorinating liquid instead of household bleach? What brand/what is the cost/where does one buy it?

Do any of the spa flush products (that are effective) list ingredients? PS http://www3.interscience.wiley.com/ link above is broken.

Would boiling the Evian water remove C02 and raise the PH?

Why doesn't hydrogen peroxide work as a spa disinfectant? Is it not powerful enough to destroy some bacteria?

Here is a paper indicating that dental plaque has recently been recognized as a biofilm: http://www.dentalcarestamford.com/pdf/Dent...%20Biofilms.pdf So the question remains; would "spa flush" be effective as an oral rinse? If so, would it be toxic?

Is dental plaque similar to spa biofilm? If so, would spa flush type products possibly be an effective method for breaking the film and keeping teeth plaque free?

Is there an advantage to using it instead of bleach? The wikipedia article seems to indicate that it is a better disinfectant and leaves less by products of disinfection. Where can I buy chlorine dioxide?

Could the nitrates be removed by giving them something to oxidize, or is the only way to remove them via replacing the water?