Dichlor To Bleach Problems ?

[sl3238]

I have a rising CYA level (been using Dichlor) and need to start using another sanitizing method....The salesperson at the pool supply store told me not to use bleach as it contains impurities (metals?) which are not good for the tub...Any thoughts?

[Mikey_in_NY]

I have a rising CYA level (been using Dichlor) and need to start using another sanitizing method....The salesperson at the pool supply store told me not to use bleach as it contains impurities (metals?) which are not good for the tub...Any thoughts?

Only that the dealer can see his potential sales drying up (not much profit in a gallon of bleach c/w Dichlor!).

Myself and plenty of others on this forum use regular Chlorox with no problem. I'm personally unaware of it containing any impurities that could damage a tub, but I'll defer to more experienced and knowledgeable members on that one.

[chem geek]

6% Clorox Regular bleach has minimal excess lye in it and it doesn't have any significant metals -- if it did, then this would tend to degrade the concentrated chlorine quickly so manufacturers of bleach and chlorinating liquid are particularly careful to use ingredients that are essentially free of metals (see this link). Clorox Regular bleach has been EPA-certified as a sanitizer for use in pools which is why it says "5.7% Available Chlorine" on the bottle. Clorox didn't bother to register it for spas probably because the market isn't bit enough (in volume of bleach used) compared to pools and the costs to do the EPA DIS/TSS-12 tests are not low.

There ARE reasons that dealers and manufacturers say not to use hypochlorite sources of chlorine (bleach, chlorinating liquid, Cal-Hypo, lithium hypochlorite), but these are due to using ONLY these products and not adjusting water balance accordingly. If you use these products as the only source of chlorine and have no Cyanuric Acid (CYA) in the water, then the active chlorine level will be too strong and will tend to oxidize hot tub covers and other components too quickly. Also, these products are not net acidic so if the Total Alkalinity (TA) level is at normally recommended levels of 80-120 ppm, then the pH will tend to rise too much and scaling can occur. Both of these issues are easily mitigated by having a lower TA level (< 80 ppm; usually 50-60 ppm), using 50 ppm Borates as an additional pH buffer, and using Dichlor initially to build up the CYA level to 30 ppm and then switching to bleach.

[EDIT] Perhaps the "impurities" he is referring to is salt (sodium chloride), but that will also come from Dichlor, though at a rate half as much as bleach. Salt isn't a problem unless it gets very high at which point the increased conductivity and chloride levels can be more corrosive to metal components including stainless steel, but we're talking about many thousands of ppm salt (even saltwater chlorine generator pools have 3000 ppm salt). Even with bleach, you would have to go 6 months without changing the water with 1 person-hour of soaking every day (and no ozonator) to get to 2000 ppm salt -- a Dichlor-only tub would need the water changed in less than half that time due to the buildup of CYA (at 190 ppm per month, assuming the same 1 person-hour per day) which makes the chlorine less effective so that the water starts to get cloudy from too slow an oxidation of bather waste and other organics. Remember that for every 10 ppm Free Chlorine (FC) added by Dichlor, it also increases Cyanuric Acid (CYA) by 9 ppm. [END-EDIT]

See Nitro's Approach to Water Maintenance for more info.

[kbaumann]

Here is the MSDS for Clorox bleach.

Clorox Bleach sold at your local supermarket has these ingrediants:

Sodium hypochlorite 5 - 10%

Sodium hydroxide <1% 2 mg/m1

Water

PH 11.9

Liquid Clorinator hth sold at ACE Hardware stores for pools has these ingrediants:

SODIUM HYPOCHLORITE 7.0 - 15.0

Water 73.0 - 87.0

Sodium hydroxide 0.5 - 2.5

SODIUM CHLORIDE 5.0 - 11.0

PH 12.0 - 14.0

QUOTE FROM HowStuffWorks: HERE

"Chlorine itself is a gas at room temperature. Ordinary table salt (sodium chloride, NaCl) is half chlorine, and a simple electrochemical reaction with salt water produces chlorine gas easily. That same reaction produces sodium hydroxide (NaOH), and by mixing chlorine gas with sodium hydroxide you create sodium hypochlorite (NaOCl). When you buy a gallon of bleach at the grocery store, what you are buying is the chemical sodium hypochlorite mixed with water in a 5.25-percent solution. You're buying salt water that has been changed slightly by electricity.

Chlorine is chlorine, so the chlorine in bleach is the same as the chlorine in drinking water and in a swimming pool. In fact, you can use chlorine bleach to treat a swimming pool or to treat drinking water. A gallon of bleach provides 1 part per million (PPM) of chlorine to 60,000 gallons (about 250,000 liters) of water. Typically, a pool is treated at a rate of 3 PPM, and drinking water is treated at anywhere from 0.2 PPM to 3 PPM depending on the level of contamination and the contact time.

Chlorine is used in pools and drinking water because it is a great disinfectant. It is able to kill bacteria and algae, among other things. Chlorine also makes a great stain remover, but not because of the chlorine itself. Natural stains (as well as dyes) produced by everything from mildew to grass come from chemical compounds called chromophores. Chromophores can absorb light at specific wavelengths and therefore cause colors. When chlorine reacts with water, it produces hydrochloric acid and atomic oxygen. The oxygen reacts easily with the chromophores to eliminate the portion of its structure that causes the color.

There has been a lot of discussion about the safety of chlorine in drinking water. It's not clear how safe or unsafe chlorine is, especially in PPM concentrations. But two things are clear:

It's a whole lot safer to drink chlorinated water than water contaminated with disease-causing bacteria. Millions of people have died from water-borne diseases, and these diseases are largely eliminated in modern water systems through the use of chlorine.

If you are worried about the chlorine in your water, all you have to do is let the water stand for a day or two in a loosely covered container in your refrigerator and the chlorine is eliminated."

[kbaumann]

I am trying to find the EPA registration?

http://www.epa.gov/pesticides/chemical/foi...4703/014703.htm

[chem geek]

EPA pesticide registration isn't particularly relevant since any pesticide must be EPA registered. That is not the same as a disinfectant that kills bacteria quickly enough to pass EPA DIS/TSS-12. For example, copper is EPA registered as a pesticide, but by itself it does not pass the stringent disinfection tests so cannot be used alone, but only to supplement an EPA-approves sanitizer: specifically chlorine, bromine, Baqua/biguanide/PHMB, or Nature2 with MPS at hot spa temperatures. The first three are OK for pools or spas while the fourth is only for spas (hot water temperatures).

[sl3238]

I guess it makes sense that the pool supply store doesnt want people to use bleach for economic reasons....I'll make the switch...Also, once you've started with the bleach, is it ok to still use the dichlor at times? I'll be away for a week and wont be able to add the bleach every day or two whereas with the Dichlor shock, I could probably have decent FC levels while away?

[chem geek]

If you want the chlorine to last long, then you can shock as you say to a higher level, but you don't do that with Dichlor -- you just do that with bleach. The bleach will last as long as the Dichlor.

You do want to add Dichlor for a day or two per month to replenish some CYA that will drop over that month, but otherwise you just use bleach (except for the first week or so when you use Dichlor to build up the CYA).

Don't forget to read Nitro's Approach to Water Maintenance (summary at the end of first post) and remember that you want the Total Alkalinity (TA) to be lower (< 80 ppm; possibly 50-60 ppm) to prevent a pH rise and you'll likely want to add 50 ppm Borates for more pH stability as well. You may also target a pH of 7.7 instead of trying to get to 7.5 all of the time. All of these parameters depend on your specific situation since the rate of pH rise depends on the amount of aeration in your spa.

As was noted in the earlier post, when you have an ozonator, it will tend to use up chlorine when you aren't using the tub, but it will also help get rid of bather waste when you do allowing you to add less chlorine after a soak.

[sl3238]

Thanks Chem Geek...Your info is really a big help..