As an aside, I've tested my phosphate levels and found 515 PPB as the number I'm settling on as an average of three tests, but I plan on no action to reduce them. I'm slightly curious where I should theoretically get into trouble with my FC/Cya ratios, but I'm honestly not too worried about it. Your 25000 PPB ought to give anyone confidence, but we've seen members with >3000 manage without undue trouble while maintaining normal FC/Cya ratios.
If anything, I'm curious how much under the suggested ratios I can manage without running into trouble. I may try running it less this summer just to find out.
Hey Patrick,
Definitely keep us updated on this goes for you! Having another data point would be great. What FC/CYA ratio do you typically run at?
PS - 515ppb.....hmmm....looks like someone took a water sample to work for testing :tongue:
Pre TFP I've had a few low FC/CYA ratios but the lowest was just 2.2% (FC 0.8, CYA 35, CC 0.1 PO4 0ppb) until this summer the pool has always been cold with no one ever really swimming in it, a glorified water feature really. I've never had an algae issue and my notes indicate that the FC was back up to 2ppm the very next day.
Out of interest I now manage a second pool, lucky me, concrete with a SWCG that is not self cleaning. Between cell cleaning the FC/CYA ratio will slowly decrease. I target a FC of 5ppm and CYA of 70ppm (PO4 = 0ppm), a FC/CYA ratio of 7.1%. I cleaned the cell yesterday and didn't think to get any readings - oops, running late for school pickup on the first day back. When I took charge of the pool the cell was badly scaled with FC at 2.3ppm, CC at 5.8ppm, CYA at 20ppm and a FC/CYA ratio of 11.5%.
Assuming that at worst it now gets to as low as 3ppm that's still a FC/CYA ratio of 4.3% so it will constantly cycle between ~7 and 4.5%.
AUSpool,
It's very interesting that you ran at 2.2%. What do you define as a "cold pool"?
To All,
In general, I'd like to reiterate that the point of phosphate removal is NOT to act as a sanitizer. One could, with a lot of money spent, try to make their pool completely oligotrophic and starve the flora & fauna to death. But that is just not a practical approach for residential pool care. The point of phosphate removal is to make the water "
less reactive" to algae so that a pool owner can have a larger buffer against developing a green swamp. By "
less reactive" we mean that, even if algae finds it's way into the water, the rate of growth is so restricted that the CT kill rate of chlorine is more than sufficient to keep it in check. That CT kill rate is proportional to the FC/CYA ratio, as the FC/CYA ratio is directly proportional to the amount of hypochlorous acid in the pool water. One only needs to maintain a CT kill rate that is greater than the algae reproduction rate in order to keep a pool clean. This is why pools that are deficient in nutrients or have secondary sanitizers in them (for example, borates or algaecides) can sometimes operate at lower FC/CYA ratios; there's nothing controversial or surprising about that. The question, of course, comes down to one of cost & complexity and what the pool owner is willing to tolerate in terms of water management.
I'm a big believer in the idea that you need to be able to accurately measure any chemical you put into your water in order to understand what effect it is having. This is why I'm generally against the use of algaecides, even Polyquat-60, because they basically operate on the "dose & pray" philosophy - dose the water with the chemical based on nothing more than pool volume and intervals of maintenance dosing and "wait & see" if it works? That to me, as an engineer, is not at all acceptable. The problem is there are methods and test kits available for measuring quaternary ammonium algaecide concentrations but they are expensive and, generally speaking, the tests are not easy to perform. So, in that case, the use of algaecides represents a cost in terms of both time and money that I think is not worth it.
On the other hand, at least in my pool, adding borates once per season (that's all it takes really) and lowering phosphates once per season, does not represent a huge cost in terms of either time or money. So, if I can deploy those two secondary methods and get reasonably good results, then they are worth it. What constitutes "reasonably good results" would be less pump run time and/or SWG output because that is the primary measure of how much FC I add to my pool. If my results wind up being a 5% difference in pump run time over the course of the season, then that's a negative result. If my pump run time is cut in half, then that's a very meaningful positive result.
So, only time will tell.....
And, as always, if you are someone who just likes a simple approach and could care less about about playing amateur pool chemist, then keeping your FC/CYA ratio at TFP guidelines is more than sufficient to operate a clean and trouble-free pool.
