Testing Questions

[waterbear]

Hi all
First of all let me say thanks for all the good information and dictation of mods and users here in the forum.
I have been lurking for the past few weeks learning all I can and am starting to feel more confident about the pool chem thing.
I still have a few questions but I will post my numbers first.

Free Ch 3 (DPD method)
Total CH 3 (OTO method)
TH 250-260
ALK 160-170
CYA 20-30
PH 7.6

I am not new to testing being a med tech for 12 years but I am new to pool testing. Let me say I am anal retentive about accuracy and precision in testing. I am using off the shelf test methods for now. I will have to wait until next year to convince my future wife to let me spring for one of Ben’s test kits she thinks I have spent enough of testing right now. I have one of the Wal-Mart 5 way test, Aquachem test strips, and DPD tablet method. The pool is 24’ above ground 52” walls so I compute around 13000 to 14000 gallons. I have a 2 hp pump and 22 in sand filter.

1. Just how accurate do I need to be? The CH color standards are not very good.
Since you said DPD tablets I assume you are using the LaMotte comparator. It is not the greatest. The Taylor DPD liquid reagent comparator is a better DPD test. The colors match up more closely. With a cya of under 30 your FC should be 1-3 ppm. when it gets to 30-50 3-6 ppm is where you should be.
2. I have my oldest do a strip test before I let them get in during the day because I work nights and am snoozing. Are they good enough to use for them to get a guess before getting in the pool?
for a quick check they are fine. Aquacheck (Hach) is one of the better strips as far as strips go. Under the Hach name they are used in the medical field for testing. I think you are being a bit anal about this...just let the kids enjoy the pool! Bumping your CYA and running the FC a bit higher is good insurance that the water is sanitized during the strong sunlight and not burning off. Keep tabs on the pH and keep it between 7.2and 7.6. chlorine is more effective at a lower pH then when it climbs up above about 7.8.
3. Is there a better method for CYA than the turbidity method?
IMHO, no. If you want to invest in a turbitity meter you can get more accurate results with the melamine precipitation test for CYA but it really isn't necesary to go to that expennse for the precision you need for your pool
4. Does oxygen shock (what can I say I got pool stored before I found this site) affect the CH test?
IF you mean does it affect DPD and OTO tests for chlorine yes it does. It will show up as combined chlorine and total chlorine on both reagents. Taylor has a reagent avaialable to use with their DPD tests to remove the interferance from MPS (potassium monopersulfate(oxygen shock, DuPont Oxone)IF you are using it you will always show combined chlorine even if there is none. Also MPS is only an oxidizer and NOT a sanitizer so don't use it in place of chlorine..alway make sure you have chlorine in the pool when you shock with it. IMHO, it is not the best choice for a chlorine pool.
5. When is the best time of day for me to test?
There is no best time as long as you test about the same time each day. that way variables like sunlight burning off chlorine are minimized.
6. Will the ALK slowly come down over time by adding acid to keep the PH down to 7.4 or do I need to go ahead and do the low PH and aeration procedure?
ALK is a measure of the carbonic acid/bicarbonate/carbonate buffer system in the water. the ALK test only measures the bicarbonate/carbonate part of it. By lowering the pH you shift the equalibrium to carbonic acid but have not actually lowered the amount of the buffer system (carbonic acid is just CO2 dissolved in water....think club soda). If you then aerate you drive the carbon dioxide out of the water (think shaking a bottle of club soda to make it go flat by driving out the CO2). As you do this the amount of the buffer system is decreased because the amount of carbonic acid goes down and the pH rises because the ratio of carbonic acid and cabonates/bicarbonate shifts back to the carbonates/bicarbonates but the equalibrium point is reached as the buffer stabilzes. Now there is less of this buffer system in the water which means you have lowered the ALK.
7. Will I ever get my life back and get less anal about the chem. in the pool?
I sure hope so, it doesn't sound like you are really enjoying your pool right now, It's not rocket science and there is a range of readings that are fine. Just get the water balanced, check your chlorine and pH an few times a week and ajust when necessary, and ENJOY YOUR POOL!!!!! (and dump the Nature2. Why add copper sulfate and silver nitrate to the water? Chlorine is a much better sanitizer and also is effetive against viruses. Copper and silver are very slow acting bacteriastats and algaestats. Chlorine is much faster acting.

I have a few more questions but I will post in the correct topics.
Thanks in advance
Steve

Hope this is helpful