A year ago I was searching for "FAS-DPD inaccurate results" and saw a newbie get flamed...the supposition is that FAS-DPD is always correct. Well, I'm not sure. Two years ago I added FAS-DPD to my old basic DPD #1/DPD#2 and "guess the color" test tubes. I only used FAS-DPD for a while and noticed I was having a lot more trouble with algae. I started comparing free CHL results with the old color test tubes as well as the pool store (they use a commercial lab type test station but I've had them back it up with titration tests). Consistently my FAS-DPD tests were off (reading way higher than actual). I rechecked my lab style beaker for 10ml volume accuracy, I replaced my reagents, I performed multiple tests to check for variation. I'm not sure what to do next. Typical results are similar to what I just got recently: color test tube says ~8, pool store lab says 8, FAS-DPD takes 24 drops at .5ppm/drop is 12ppm. Before I throw the FAS-DPD stuff out I thought I would post here and see if there were any ideas.
Related algae question: I'm trying to keep my CHL between 6-9 to keep algae at bay (CA is ~50). In reality this means pushing it up to about 12 and letting ride to 6 before adding CHL - about every other day. Circulation is about 12 hrs a day - most of which is while the pool is getting direct sunlight and cycling 30 minute intervals while dark. The pool is vinyl, 25k gallons, gets moderate sunlight in NC due to tree cover, and barely gets to 82 degrees while daytime highs for the past 3 weeks have been in the mid-90's. The water is crystal clear and I keep the pool very clean. The pool is otherwise balanced to TFP numbers. Problem (I think): Every morning I come out to a slight haze of patchy green algae growing on the sides and bottom. It brushes off pretty easy into a cloud and reforms in patches the next AM. I did add a bottle of algaecide - I don't think that is highly recommended here but I'm ready to try anything. I did push the free CHL up to upper teens for a shock but didn't seem to help. In years past the water was colder (we cut some trees) but I either had algae or I didn't -- it would not appear unless I let the CHL levels drop too much. My old CHL levels were more like 3-7 and that worked ok. Is this normal as the temp has gone up to 82 and it's getting a little more sunlight? or is there something else I can do to stop having to brush every day? Thanks!
Related algae question: I'm trying to keep my CHL between 6-9 to keep algae at bay (CA is ~50). In reality this means pushing it up to about 12 and letting ride to 6 before adding CHL - about every other day. Circulation is about 12 hrs a day - most of which is while the pool is getting direct sunlight and cycling 30 minute intervals while dark. The pool is vinyl, 25k gallons, gets moderate sunlight in NC due to tree cover, and barely gets to 82 degrees while daytime highs for the past 3 weeks have been in the mid-90's. The water is crystal clear and I keep the pool very clean. The pool is otherwise balanced to TFP numbers. Problem (I think): Every morning I come out to a slight haze of patchy green algae growing on the sides and bottom. It brushes off pretty easy into a cloud and reforms in patches the next AM. I did add a bottle of algaecide - I don't think that is highly recommended here but I'm ready to try anything. I did push the free CHL up to upper teens for a shock but didn't seem to help. In years past the water was colder (we cut some trees) but I either had algae or I didn't -- it would not appear unless I let the CHL levels drop too much. My old CHL levels were more like 3-7 and that worked ok. Is this normal as the temp has gone up to 82 and it's getting a little more sunlight? or is there something else I can do to stop having to brush every day? Thanks!
