Trouble Keeping Chlorine

[mkamp1515]

Good morning. I have a SWG, 20,000 gallons, Pebble Tec.

I am having some trouble keeping chlorine in the pool. Usually I do not. But I live in the Fort Worth, TX area and it has been 100-107 degrees everyday for a couple of weeks. My latest chlorine test was in between 1-2. I was able to keep it higher just a few weeks ago when it was not so hot. My CYA level is 40-50 which is usually good (I was keeping my chlorine at 3-5). I have been running my pump 11-12 hours a day and all seems fine (no error lights, salt cell is very clean-no scale). I even superchlorinated earlier this week. I decided this morning to add some granular shock...not a whole lot though. I also decided to put in more CYA because I thought maybe I did not have enough "sunscreen". Is this the proper course of action? I have very clear water and the other readings seemed fine (alk-90, pH-7.6, hardness 250, less than 100 phosphates).

This kicker is that I am going on vacation for a week beginning tommorrow. I do have a house sitter and I am going to leave him some pool care instructions (I will also leave the chlorinating % at 90%). Should I just tell him to add some shock every few days? Any help would be great?

Thanks,
Mike

[duraleigh]

I would shock the pool.

Chlorine is consumed by 1) the Sun and 2) organics in the water. While there may have been a little increase in the exposure to the Sun during these long days, I suspect the beginnings of algae is a more likely culprit.

It's a cheap fix, too. Put in enough Clorox to bring your Cl up around 25ppm, preferably in the evening, and test the next AM. If it has dropped noticeably (more than 2 or so ppm), that was the issue.

I'd bring it right back up to 25ppm tomorrow AM. That'll give you some residual while your away and protect against further algae development.

[mkamp1515]

Thanks. I am going to bring up the chlorine by shocking it. I talked to the chemistry/service folks from my pool builder and he indicated my CYA was too low for the heat we have been having here. I will bump up my CYA and shock the pool and have more shock on hand for my housesitter to put in if necessary. That should help prevent any algae blooms.

Thanks for your advice.

Mike

[aylad]

I live close to Shreveport, and was in your neck of the woods last weekend. My Cl drop has increased, too, and I very strongly suspect that the killer days we've had over the past month or so is your culprit, more than algae blooms. I agree with bumping the CYA up (I always run a high CYA pool anyway, and that's why) and seeing if that takes care of the problem. YOu're going to have to be extra vigilant about keeping the algae down during this heat, though, so shocking often is a good idea.

Janet

[mkamp1515]

Yeah. I just threw in some more shock and pumped up my CYA (70-80 now). My Chlorine level is at least 10ppm and probably more as that is how high the strips go. I had my water professionally tested and luckily my CC was 0, so I do not think I had the begginnings of algae and neither did they. I have left some shock with my house sitter and instructed him to test and put in if necessary. Should be fine till I get back.

Thanks for the help.

Mike

[chem geek]

Thanks. I am going to bring up the chlorine by shocking it. I talked to the chemistry/service folks from my pool builder and he indicated my CYA was too low for the heat we have been having here. I will bump up my CYA and shock the pool and have more shock on hand for my housesitter to put in if necessary. That should help prevent any algae blooms.
Mike

Most SWG manufacturers recommend the 70-80 CYA level that you have now moved to. The reason is that the salt chlorine generation cells operate more efficiently if there is sufficient CYA around to "tie up" the chlorine as fast as it is being generated so that it does not build up and slow down the generation process.

If you are going to keep your CYA high at 70-80, then you need to keep your FC at 5-10 ppm in order to have adequate disinfection and prevent algae. However, having your CYA at this high level along with the required FC level will have you lose more chlorine per day than you would at a lower CYA level (and correspondingly lower FC level). See Ben's Best Guess CYA Chart. On other forums specific to SWG, some people think that Ben's chart is overkill and not as necessary while others think it is. So, if you want to play it safe, go with Ben's chart (which is around 7 ppm FC). If you want to play it loose, you could go with lower FC, but I would not go below 2 ppm FC in any case since that it is the limit of disinfection protection -- probably stay with at least 3 ppm FC if you go this "riskier" route (which most SWG users would not call risky).

Along with others, I am trying to determine what the true proper chlorine levels are to prevent algae and to shock (kill) algae both in non-SWG environments (where Ben's table has been reliably proven) and in SWG environments (where Ben's table is a little controversial).

Richard