Split off of Downsides of SWGs, fact or fiction?. JasonLion
It's apparent from this thread that there are unexplained differences in the results obtained from pool to pool. Three years ago I installed a Pool Pilot Digital SWG system. For 2 years, I added about 1 to 2 quarts of acid per week, after keeping the TA in the 70-80 range and keeping CYA around 80 to 100. I found on occasion that my lack of diligence on a daily basis allowed the pH to climib as high as 8.0. While with a liquid chlorine pool the lack of diligence results in a green pool, I found with an SWG the lack of diligence results in calcium deposits on the sides of the pool.
Before the SWG, I would test the pool once a week when I added chlorine. With the SWG, I found I had better check the pH and TA on pretty near a daily basis, or else. This became something of a pain. And a disappointment, when despite my best efforts the pH still got way to high too many times (what can you do if you have a business trip that takes you away for a week), and damaged my pool surface (5 year old Marsite).
So I decided to upgrade the Pool Pilot to a Total Control system, which controls pH automatically. The only part compatible with my existing system was the SC-48 cell, so the money spent on the basic system went to waste, since I would have purchased a TC system had I known of the constant demand for acid using the basic system.
Results: much easier to deal with. The TC keeps the pool blue, and the pH under control. And I only test once a week, to make sure things are in line. And on a weekly basis, what I find is that I have to add Alkalinity Increaser to offset all the acid the TC pumps into the pool on a constant basis (when it drops to 40 or 50, I add 5# of AI to get it back to 70 or 80). And every month or so, I have to add acid to the acid tank. Over the past six months, I have added 65 pounds of Alkalinity Increaser and 20 gallons of acid.
So, with a TC system, I find I can leave the pool to itself and test it once a week, and add something once a week. Same as with a pool without an SWG system. The weekly dose of Alkanlity Increaser is much easier to carry around than the weekly dose of liquid chlorine, and the TA does not rise as fast to alarming levels as the pH could in just a few days with a basic SWG. Score one for the TC over the SWG and liquid chlorine. But the monthly need to add 3 gallons of acid to the acid tank is unique to the TC pool. I guess you could compare that inconvenience to the need to shock a liquid chlorine pool occasionally. I've spoken to tech support about this, but there is no answer for my pool that they have. Maybe if some chemist came down and studied my pool as if it were his main job for a month, I'd get some answers as to why Waterbear's pool needs no attention and mine needs both attention and regular additions of chemicals. That's not going to happen, obviously.
On balance, the TC pool I have is somewhat easier to take care of than when it was a liquid chlorine pool, so I'm keeping the system. But it's initial cost was significant, and I don't know that I would do it again. If any part of the system fails after the warranty runs out, I don't know that I'll spend the money to fix it.
For those who don't have to add acid to an SWG pool, I'm mystified and disappointed I am not one of them. But for those whose pools will need acid (and you won't know until you install an SWG), it makes you wish for a way to add chlorine that does not require having to add chemicals on a weekly basis. Maybe that's just wishful thinking.
As for the look and feel of the pool water improved with an SWG, that's hard to say. I'd like to think it's somewhat better, but if it is, it's not really obvious. In my pre-SWG days, I was pretty good about keeping my chlorine in the 3.0 range, so never really had any bad effects from too much chlorine. And my pool looked good then, and it looks good now.
I keep a log of everything I add to the pool, and all test results. Goes back 4 years for my current pool, and several more before that on the pool at my former house. By now, it's quite a database. For what it's worth, I have a 17.000 gallon pool with an SC48 cell set to power level 1 - same as it was when it was a basic SWG system. The TC controls ORP and pH automatically. I have ORP set to 650, which roughly works out to 3.0 to 8.0 Free Chlorine levels (which I test weekly with a Taylor FC test kit).
P.S. There are other details with a TC system that make it different from a basic SWG system: you have to keep the CYA at or below 60 to allow the ORP meter to work properly (it's unreliable with normal CYA levels), and the lower the pH the higher the ORP at a fixed level of Free Chlorine. That's good, because the higher the ORP, the less the SC48 works to generate chlorine and consequent acid demand. Thus, I keep CYA between 30 and 50, and set the TC to keep the pH at 7.40. (I tried raising that to 7.50 to reduce acid demand, but after a short delay the acid demand was equal to or worse than keeping it at 7.40, so I put it back. The higher the pH, the more the SC48 has to work to maintain an ORP set point). Supposedly, ORP is the real measure of anti-bacterial action, not Free Chlorine. There is a persuasive (but quite technical) explanation for that, which I'll leave to others.