Best Guess Table

[KurtV]

Is "Ben's Best Guess Table" too conservative for some residential pools? I've seen more than a few people here claim to keep their chlorine at levels significantly lower than the Best Guess Table calls for for a given level of CYA with good results (no algae, no known cases of pathogen transmission through the pool water, etc.). Are they just lucky or might it be safe to keep lower levels of chlorine in certain circumstances? Is Ben's table heavily based on his experience with commercial pools? Is there a safety factor built-in to the table?

Without knowing and controlling for the myriad variables (bather load, accident-prone kid load, leaves and other vegetable matter, sunlight, etc.) that affect chlorine consumption, there would obviously be a good bit of guesswork involved in refining the table at all. However, given all the concern about safe chlorine levels it may be something worthy of further discussion.

I'm not advocating that anyone run lower levels of chlorine than Ben recommends; I'm just suggesting that based on some (admittedly sketchy) anecdotal evidence, some further discussion/inquiry might by in order. Short of that, should the table be treated as more of a starting point or guideline than an absolute? That may even have been Ben's original intent but almost everyone here (me included) now treats it as Gospel instead of as a guide.

(Just some food for thought and discussion; I'm not looking to start an argument.)

[mas985]

I know from experience that with an SWG, you can keep it much lower than the table. My CYA is now at 70 ppm and the chlorine level at 2 ppm without any problems but I have not had a dead cow fall in the pool yet.

[Wayne LaBanca]

My bather load is very low, much lower I'm sure than what Ben's guide is estimating, but I still keep my levels based on the guide. Heck, It costs me 12.00 a month in CL, I'm not going to mess with it. If I'm going to get that frugal (And I could, I live in New England) I should pack it up.

For acedemic purposes, It may be interesting to find out (I'm not volunteering), but if you get that close to the edge you would probably find it is too varied to have any public value.

Wayne

[KurtV]

My bather load is very low, much lower I'm sure than what Ben's guide is estimating, but I still keep my levels based on the guide. Heck, It costs me 12.00 a month in CL, I'm not going to mess with it. If I'm going to get that frugal (And I could, I live in New England) I should pack it up.
Wayne, Cost wasn't my concern. I was really just wondering about the basis for the tabel and whether it might lead to unecessary overchlorination of some pools.

For acedemic purposes, It may be interesting to find out (I'm not volunteering), but if you get that close to the edge you would probably find it is too varied to have any public value.

It would be interesting to collect and analyze some empirical data (e.g. daily chlorine level and CYA, hours of direct sunlight per day, bather loads, microbe counts, algae outbreaks, etc.) from a large number of residential pools and try to find the correlations. It's way over my head from the technical, monetary, and time standpoints. I guess that's why Ben came up with the table.

Wayne

Please don't get me wrong. I think the Best Guess Table is great and I'm confident that the worst it might do is cause some people to overchlorinate their pools somewhat and probably not harmfully. I don't worry very much (really, at all) about the overchlorination issue in my pool, but it's obvious from reading some of the posts on this forum and others that there are plenty of people who worry about it a great deal. If there's a safety factor built into the table maybe people could be more confident in playing around with the levels a little more without too much risk of infections and algae infestations. On the flip side of that, the shock levels in the Table don't seem to have much wiggle room; people who fail to reach those levels, even by a little, often seem to have trouble clearing algae.

[mas985]

For me, the table is for no fuss. Follow it and it is unlikely you will have any problems.

However, for those willing to take some risks with an occasional algae bloom, they can push the limits a bit and see what happens.

[CToon]

I've noticed that whenever I've let it drift toward the low end of the scale, inevitably thats when I'm most succeptable to problems. Our pool has a cya of 50 , so the range 3-6ppm . I can let it go to around 2 ~ 2.5 without worrying too much , but I cant leave it there for long without CC raising or algea taking off

[prh129]

I would think that given the wide variation of pool conditions (different climates, trees vs. no trees, bugs, rain yada yada yada) these numbers probably work well no matter what. If you tried to build a table that took all of these factors into consideration, it would take a lot of work and it would probably be huge.

I would also think that Ben's table allows for some wiggle room - if you don't get to test for a day or two or have more people in your pool one day or there's a rainstorm, whatever, then it won't cause your pool to go south whereas if you keep it right at the stable point then any little disturbance could put you over the edge.

Also it seems to be one of Ben's goals to make pool care easy for people so rather than have people figure out their minimum chlorine level, here's a universal guide that is reasonable and works. Given that 4 ppm of chlorine is considered acceptable in drinking water, these numbers don't seem like much of a concern.

Peter

[cleancloths]

I just posted something similar to this question elsewhere today. I have had my pool for 8-9 years and have CYA around 30-40 and chlorine at 1-2ppm and have never had any algea or other problems and the water is always crystal clear. I guess it is like gas mileage, your mileage may vary.