CYA level and chlorine level and pool store recomendation

[Fishcrazy]

Well the last two days ahve FC =3.5 and seems to be holding there. I have the floater diled down to a 10000 gal pool size in this 18000 gal pool. The pucks seem to be lasting quite a while at this setting. Be interesting to see how long three of them will last in my pool. Do they suddenly get soft and dissolve faster or are they consistant till they are completely gone? Wondering if these last a week say if I could expect to be able to just go to 6 tabs for a two week period? My pH seems to be steady at 7.2 and I have not tried to raise it any. If I did raise the PH would that change anything with the amount of chlorine that I am using?

On another note I am about to install a timer for the pool pump. I have been running the pool filter 24/7 but dont feel that this is necessary. Any suggestions for a scheule for a 27 round 52 inch pool. I was thinking about 16 hours a day. Thanks in advance for any and all advice.

[chem geek]

Trichlor tabs dissolve fairly slowly and fairly evenly. They usually don't fall apart. The rate of dissolving will slow down somewhat when they get much smaller since that rate is roughly proportional to the surface area. The pH should be dropping given your fairly low TA of 50 that you last reported. Is the pool covered or uncovered? If you were to add 10 ppm FC to the pool using Trichlor and that chlorine was used/consumed at about the same rate it was being added, then the pH would drop from 7.2 to as low as 6.8 except for carbon dioxide outgassing. So normally you have the pH start out higher when using Trichlor and usually have the TA higher as well. Even if you started with a pH of 7.7, with the low TA the pH after 10 ppm FC would end up at around 7.0 if there were no outgassing.

As for pump run times, you usually figure on one turnover per day but can adjust to keep the water clear. The right amount depends on your circulation. If it's really good, you can sometimes go shorter; if not, then longer; but one turnover per day is pretty typical. Note that an above-ground pool often has terrible bottom circulation since there aren't usually many returns and there isn't a floor drain. Pointing a return diagonally downwards sometimes helps with circulation.

[Fishcrazy]

I have not run anything but the Cl test and pH since I started these Trichlor tabs on Sunday when my FC was 2.5. I dont have the pool covered but the tree canopy over the pool is considerable affording no more than 2 hours of direct sunlight per day. I guess I need to figure what the flow rate of this 1 1/2 horse Hayward is to determine the turnover time. Thanks for the tip on the circulation of the bottom water.

If Im hearing you right I need to get the TA up some more and prior to leaving the pool for the two week trip I need to make sure that the Cl is either up high around 7 or more and the pH is elevated abnormally high? I have only been feeding trichlor for 3 days and pH seems to be holding steady at 7.2. We will see what happens with tomorrow morning's water test. I think I will test the CYA abd TA also tomorrow. What would I be looking to get the TA up to? Thanks for the help again.

[chem geek]

Your few hours of sunlight explains some of what is going on -- namely that your chlorine usage is probably low. If I figure that it is only 1 ppm FC per day, then in one day the pH would only drop from 7.2 to 7.15 so not be noticeable and that assumes no carbon dioxide outgassing. If you are going to be gone for a week so we figure 7 ppm FC, then the Trichlor will lower the TA by around 5 ppm so I would just raise your TA by 10 ppm to 60 ppm and your pH to 7.7 before you leave. That will have the pH drop to no lower than 7.2 after a week, assuming the 1 ppm FC per day assumption is correct. That seems reasonable. You don't have to raise your TA way up because you'll probably be frustrated lowering it again for pH stability when you return (I assume you have the TA very low for pH stability when using bleach or chlorinating liquid -- if not, then raising it to 80 ppm would be OK).

[Fishcrazy]

Today the water test surprised me a bit. pH=7.0, FC=3.5, CC=.5 or less, TA=40, CYA= 30. Surprised to see the CYA down a bit especially since adding trichlor. But it is what it is. I am going to raise the pH to around 7.4 to 7.5 and the TA to around 60 and see what happens from there. I am beginning to think I will not be able to make it two weeks at the time away without some intervention by someone to add some chemicals to bring the pH up or maybe I could raise the pH to say 8 when I left and expect the decrease of 0.05 per day to bring me to pH = 7.3. Would there be any danger in taking the pH to 8 right before I leave? TA seems to be falling rather briskly. Looking like a raise to 80 would be a good Idea prior to taking off. Maybe higher? I am not intentionally keeping TA down as I did not know that a low TA would promote pH stability when using bleach. I was under the impression that my TA needed to be raised from my initial levels to promote stability in pH. Glad I got that straight. What would be a good TA level when using bleach? Thanks chem geek! I really appreciate the insights you are providing.

[chem geek]

The CYA test is hard to read accurately so variation of 10 or 15 ppm is not unusual and doesn't mean it actually dropped. Going two weeks without any maintenance on the pool is a big stretch. At least with your low chlorine demand you could probably load up enough Trichlor pucks/tabs to last long enough assuming you turn down the feeder slats appropriately. Yes, you could raise your TA level which will help keep the pH up in spite of the Trichlor assuming the pool remains uncovered. Over two weeks, with 80 ppm TA and starting with a pH of 7.8 (I wouldn't go to 8.0 as you might get some metal staining if you have some metal ions in the water) you would end up as low as 7.05 in pH though in practice it will likely be higher due to carbon dioxide outgassing -- a guess would be 7.2. So that might be OK. A TA of 100 ppm would end up no lower than 7.1 in pH (this all assumes 1 ppm FC per day added from the Trichlor and consumed/used). So you can probably raise the TA to the 80-100 ppm range, load up the Trichlor tabs, and be OK, but if the feeder is set too high then you might run out while if it is set too low then the chlorine level could get too low. It's dicey and tricky to get right which is why automated systems and especially helpful neighbors work out better.

If you were always going to use Trichlor, then your TA could be at 120 ppm or even higher, but there's not much sense in getting it that high if you are going back to chlorinating liquid or bleach upon your return.

[Fishcrazy]

I figure I may have to call in someone to check on the pool. I dont feel like I should impose on the neighbors this much though. And if they dont know squat about pool water then they probably will be somewhat reluctant to take on this responsability.I just dont know if it is too much to ask.

Keeping the pool covered is going to be mandatory as the leaves would surely clog the skimmer up in short order. That is unless I enlist the neighbor's services. I sometimes clean the leaves from the skimmer 3 times daily.

Im not yet defeated on this working but it sure seems like a lot of ifs here on my situation. I appreciate all the advice chem geek! I have not done any water testing today yet. Will get to that though soon.