Shocking

[chem geek]

Chem Geek -I have just read through the CPO trianing and it is more of the same information I am tryng to use to possibly make chlorinating my pool easier, so Thank you. Though I dont understand why everyone keeps going back to the fact I only want to chlorinate my pool weekly? I never said this and to be clear it is not my intenton. Until this winter and dealing with trying to get our pool fixed, did I become aware of the relationship betweeen the CYA and Cl. SO upon opening, I started the process of trying to get that level down as soon as it became aparant that mine was definately out of control. From reading the forums the only way I have seen to get CYA out is to drain and then use diffent chemicals so it does not rise like that again. Hence I will only be shocking with the burn out Burn out 35, if I even need to shock at all. Still though come the issue of what should I run my CYA out since I do have the problem with all of the newly chlorinated water going into a 8 inch baby pool, and other features, and it uses the chlorine to quickly since the water is so shallow. I assume a bit higher than many run it, but I have no clue where??? That was also why the question about the UV sanitizer has come into question. The pool builder also want to stop dumping so much into the pool, again maybe shocking but true. They feel as though since they did not do a two pump system to run all of our water features, and it can not be retrofitted to do so, if we were able to have an additional element to deal with the sanitation, it would definately reduce the chemical consumption. As far as the UV, this is soley their thoughts, but I have asked the qestion several times and not gotten an awnser, could my extrely high CYA of 500 or more be the main contributing factor to our bi-weekly shocks, high chlorine tab consumption and our need to pour one gallon of chlorine into each pool feature, that sit empty until we actively turn them on, to sanitize them so that all the crap does not get in the pool and have the possibily to cause more problems. They are all in agreement to try your methods but due to the large number of water features we will most likely always use more than their average pool customers.

I hope you guys might have a suggestion as to this, but if not then I guess I will give up and just do whatever. But not all pools are the same and maybe unfortunately a forum like this is not the place for someone who doesnt have a 15,000 gallon oval liner pool. Our back yard is a modified version of a resort pool. Lots of differnt aspects to deal with and I was just trying to do it different and see if anything changes. Thanks in advance if you have some suggestions, and if not sorry I upset eveyone.

With such a high CYA level and not having a proportionately high FC level, algae is able to grow faster than chlorine can kill it. That is what leads to a very high chlorine demand, even if you don't see any visible algae since algae may not be visible until it gets numerous enough and clumps to reflect/absorb enough light. The amount of active chlorine (hypochlorous acid) in the water that is the disinfectant that kills bacteria and that kills algae and prevents its growth is proportional to the FC/CYA ratio. This is why at higher CYA levels if you don't proportionately raise the FC level that problems can occur, including unusually high chlorine demand from trying to keep up with killing nascent algae.

I don't understand why you are opposed to getting chlorinating liquid from a pool store that is more concentrated (typically 10% or 12.5%) if you don't want to carry as much 6% bleach. Even if it's more expensive per FC, it won't be that much more. However, lithium hypochlorite (which is the chlorine in Burn Out 35) is VERY, VERY, VERY expensive for the chlorine you get. Yes, it is 35% available chlorine, but PER FC it is over 5 times as expensive as bleach or chlorinating liquid (see Cost Comparison of Chlorine Sources). Obviously you can use it if you want to, but I want to make sure you understand the extraordinary premium in price you are paying to carry 1/3rd to 1/6th the weight. Also, you refer to using it for shocking, but what will you be using for regular chlorination if you are going to be dosing more than once a week? If you use stabilized chlorine such as Trichlor tabs/pucks, then that will increase the CYA level. The following are chemical facts that are independent of concentration of product or of pool size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it will also increase Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it will also increase CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it will also increase Calcium Hardness (CH) by at least 7 ppm.

The builder doesn't know what he is talking about if he thinks that a UV system is going to help you reduce your chlorine amount. Use your head here and think about where chlorine gets used. The greatest loss of chlorine daily is from breakdown from the UV in sunlight (the UV system will also breakdown some chlorine, but not that much since most are woefully undersized). There is less breakdown with higher CYA levels, even with proportionately higher FC levels, but you'll still lose anywhere from 15% to 50% of your FC level depending on your CYA level (15% loss at around 100 ppm CYA, 50% loss at around 40 ppm CYA, assuming a full long day of sun at the peak of summer). Your chlorine is not getting lost more quickly due to the shallow water. Over 97% of it is bound to CYA and does not evaporate. All a UV system is good for is killing Cryptosporidium parvum oocysts which are not a problem in residential pools unless you let some sick person with diarrhea into your pool. It's an issue in commercial/public pools where one person can infect dozens or more.

After loss from sunlight, the next largest chlorine loss in a residential pool is either thermal loss at around 0.3 to 0.7 ppm FC depending on water temp or it's bather load IF the pool is small and you have a lot of bathers or people urinating in the pool. After that, there is a small loss from chlorine oxidizing CYA at around 0.1 to 0.3 ppm FC per day. However, in your pool right now with the very large chlorine loss, it's mostly trying to kill algae because the active chlorine level simply isn't high enough. So if you don't want to take care of that directly by lowering your CYA level and shocking to a higher FC and thereafter maintaining an appropriate FC/CYA, then there are other ways for you to spend money at the pool store to prevent algae growth including the use of algicides (PolyQuat 60 being the best) and phosphate removers and even copper ion products if you don't care about staining your pool surfaces or turning blond hair greenish. Obviously, we don't recommend those here (except for PolyQuat 60 if one really wants to have some supplemental algae prevention; 50 ppm Borates is another alternative that can help a little), but it's your pool and you do whatever you want with it.

I think what got people offended here was your digging in your heels that you would not stop using BioGuard or other pool store products before even listening to us about the pros and cons of various products. This site is all about education and if you come here with a closed mind then that puts people off. If after learning the truth based on actual chemistry and real-world experiences you still decide to use more expensive pool store products, then that is fine since you will be doing so with the knowledge of the pros and cons of such choices. There is no question that using Trichlor pucks/tabs can be more convenient for some people and if they then deal with the side effects by buying other products at additional expense, then so be it -- that's a cost/convenience tradeoff made as an informed decision.

Also, if you want the most convenience and have money to spend, then consider getting a saltwater chlorine generator system. Otherwise, as Ben says, a pool service is the easiest if you've got money to spend.