I'm new here. However, I've spent a lot of time online recently reading about pool chemistry through various Web pages, how-to's, and forums. A member of another forum mentioned this one, so I thought I'd try my luck. I'd appreciate any help you can offer.
We recently purchased an above ground that had been bought at a pool chain store and never installed (back in 2005). It was in boxes and new, so we proceeded with the purchase and installation. The local installers were the same ones that are used for the same retailer here in our area, although this pool was purchased out of town originally and the folks moved.
The pool is a 18 X 33 buttressless Oval (I know the manufacturer but am not sure that I can post the name here). It has a wall height of 52". Our average depth is around 46". The first problem is that we've found varying calculators and formulas for determining volume. We have finally arrived at an estimated (nice round number) of 13,250 gallons at current fill depth, but I'm still not comfortable that this is correct. Some people have said our pool is 14,000 gallons and others have said 19,000 - big difference! Anyway, I have also not found anything that 100% clarifies that if 14,019 gallons, if this is assumably filled to the top of the wall or at average depth (how do these calcs work??). I think the total we finally went with was the book from our SWG and estimating around 3.85 feet as the average depth. Anyway, the pool has a sand filter with a "proclaimed" 2.5 HP motor - which I won't get into that, but from what I understand it is only a 1.5 HP.
We have a SWG. The salt level is 3000 PPM.
We are using a regents test kit that is OTO based for chlorine. Here are the levels:
CYA: 50 (we added some to get here but have not added more yet)
Hardness: N/A - have not tested due to vinyl pool
I made the mistake with test strips of misinterpreting the TA and added 4 lbs of baking soda a week or so ago. We since got the regents kit and realized what had happened. TA was around 230. So, We've added Muriatic Acid twice now, which has brought it down some, but not nearly as much as expected. A couple of things might be going on - 1. water volume estimate wrong??? And / OR 2. Adding acid improperly.
I read somewhere that to lower alk you have to add acid directly to the water to cause it to gas off the CO2. Is this correct? My concern is there is no "deep end" and this is a vinyl pool. So to make it safer to handle and to reduce the splatter, we mixed it with a bucket of water and poored it gingerly around various places on the perimeter of the pool away from the wall. So this is one major part of my question . . . are we doing this right?
I noticed both times the PH came down a tad (from like 7.8 once to 7.4 and from 7.6 to 7.4) but we were very conservative in acid use. However the second time I used twice the acid (16 oz first then 32 oz next) and the change was about the same proportion. Also, after circulating the pool over 8 hours I noticed the ALK was still at 190, which is where it was approximately when we began the second time with the Acid (I think it was at around 200). So this began my concern about whether we are adding it properly or not.
Finally, I know we need to add CYA - but I wanted to get the alkalinity right. My thinking is since we have a SWG and no other easy way to aerate the pool, I can let the SWG do the aeration. Right? I have read about dangers of Chlorine gas, but is it safe to circulate the pool say 4 hours on low and then turn on the SWG to do the aeration? The point about CYA is if we add more, then the chlorine will not dissipate as easily, thus hurting me on the need to run the SWG for aeration to get the ALK in control and PH back up. Incidentally, the SWG manufacturer suggests 80 PPM for CYA and I've also read that 90 PPM for ALK is best to reduce scaling with cell life on the SWG.
Please help. I'm thinking we are close to a solution, but there are obviously a few important questions that are unanswered in my mind.