New China Shop Topic: How Accurate is the Pool Calculator?

[madwil]

That's why it's a place holder...
0's at the end of a number, without decimal places, are not significant.
0's after the decimal, before numbers, are not significant if 0 precedes the decimal.
Otherwise, you could call 2 ppm .000002 and say it's 6 sig dig, when it is only 1!
Consider scientific notation- a.bc x 10 to n power- a.bc is sig, not the location of the decimal point, with regards to accuracy/precision of measurement
When you mult/div numbers, the lowest number of sig dig in any of the factors is the number of sig dig in the product
When you add/sub, the number with the highest multiple of 10 becomes you last sig dig (1,250 + 2, is still 1250 for significance...)

[waterbear]

People, we are losing sight of the fact that we are talking about a swimming pool and the amount of water in the pool needs to be accurately known (and not rounded off to the nearest 1000 gallons or so) or this all become moot.
It's a swimming pool, not a science experiment and in the real world we are just splitting hairs here that are not important. Now I am the first one that insists in precision and accuracy when doing a scientific experiment (lest anyone forget I have a very similar scientific background like chem geeks) BUT you need to take in account your largest margin of error (which in our case would be the volume of water in the pool) and not try and get a precision smaller than this limiting factor because it is invalid! Yes, I know that errors are cumulative but if we are talking about errors that differ on such a significant order of magnitude they become insignificant!

We also have to take into account the precision of our testing methods and any errors introduced by our testing methodology.

What it boils down to is that the 'guestimate' that CarlD provided of one gallon of liquid chlorine adds approx. it's strength of FC to 10000 gallons of water is about the amount of precision that we can expect in real world situations of pool maintenacne and it is most certainly close enough for our purposes of maintaining a pool.

(If anyone is old enough to remember using triple beam balances or balance pans remember that the weight is taken after three equal oscillations of the pointer and not when the pointer had come to rest. This is my point, you have to realize what the limit of your precision is.)

[Watermom]

Y'all just need to go swimming and have some fun.

[CarlD]

You don't think arguing is fun???? That's why we have the China Shop.

There's difference between measuring with something you know is off and correcting for it: "My speedometer always reads 5mph fast"
and something you believe is correct and isn't "But Officer, I had it NAILED at 55mph on my speedometer, not 65".

Can't go swimming. It's nasty, cold and raining. Therefore, arguing is a valid alternative source of fun!

Carl

[waterbear]

Can't go swimming. It's nasty, cold and raining. Therefore, arguing is a valid alternative source of fun!

Carl

Explains everything!
Beautiful sunny weather here, been swimming for several months now and the pool stays a comfortable 85 degrees without my heat pump running! Getting ready to jump back in before I start grilling!