Can someone give me an idea how many gallon pool this is?

[coastal]

I was guessing about 12-15,000 gallons but then I found this drawing in the builders package.

 

[Guest]

Average depth times square foot time 7.5 should get you pretty close!

Bruce

 

[PaulR]

It's close enough to rectangular that you can use 30x18 as the area, for starting point. Once you have a starting guess, if you really want you can do a chemical test and see what you get.
--paulr

 

[coastal]

so lets see, 18x30=540 Then if I figure 4.5' avg depth x 540= 2430 X 7.5= 18225 gal or there about.

That's a lot more than my guess. Now I'll narrow it down with a known quantity of a chemical change?

 

[PaulR]

If you add a known amount of some chemical to your pool, and measure the levels before and after, then you can calculate how many gallons. The most accurate test is for chlorine, so usually you'd use bleach.

Now, 1 gallon of 6% bleach in 10,000 gallons will raise FC 6ppm.
Therefore, a 182 oz jug (1.4 gallons) in 14,000 gallons will raise FC 6ppm.

For this procedure, you probably want to use a 25ml sample for your FAS-DPD test, to get the 0.2ppm accuracy. What you do is:
1) Make sure you don't have any algae or other organics using up chlorine.
2) Wait for the sun to go down (another source of FC loss).
3) Run the FAS-DPD test with a 25ml sample.
4) Add your 182-oz jug of Clorox 6%.
5) Let the pump run for an hour or two.
6) Repeat the FAS-DPD test with a 25ml sample.
7) Take the difference of the two FC readings.

Now calculate your pool capacity = 14,000 x (6 / FCdiff).
--paulr

 

[polyvue]

Now, 1 gallon of 6% bleach in 10,000 gallons will raise FC 6ppm.

Oh, not to add worry to worry, but you would want to be SURE that the bleach is actually 6%, right?

When I shocked my pool a couple of weeks ago (known quantity of water, unknown quality of bleach) I applied 10% sodium hypochlorite [1 month old liquid chlorine from pool store] that I determined to be only 6.5% strength and a jug of grocery-store purchased [1 day old] regular Chlorox bleach, whose strength I estimated to be 4.26%.

I know there's a procedure somewhere on this forum to test chlorine strength... :idea: just not sure where.

 

[PaulR]

Now, 1 gallon of 6% bleach in 10,000 gallons will raise FC 6ppm.

Oh, not to add worry to worry, but you would want to be SURE that the bleach is actually 6%, right?

When I shocked my pool a couple of weeks ago (known quantity of water, unknown quality of bleach) I applied 10% sodium hypochlorite [1 month old liquid chlorine from pool store] that I determined to be only 6.5% strength and a jug of grocery-store purchased [1 day old] regular Chlorox bleach, whose strength I estimated to be 4.26%.

In general I would expect 6% bleach from a grocery/big-box store with reasonable turnover to really be 6%; the half-life at air-conditioned temperatures is multiple years. If the jug hasn't collected dust I'd expect it to be okay. But, of course there's no guarantee.

I know there's a procedure somewhere on this forum to test chlorine strength... :idea: just not sure where.

That test is based on the fact that 1/2 tsp 6% in 4 gallons is pretty darned close to 10ppm. Again you want to test your sample before and after, unless you're using 4 gallons of known chlorine-free water (e.g. distilled). Also you need a bucket big enough to hold 4 gallons.
--paulr