Yah, sorry, I don't have any experience with that. You'd think they'd know how much water they're carrying, right? You might still be able to use the meter trick, depending on how your fill progresses. If they show up with a 5000 gallon truck, then another one, but you still aren't full, you can use your water meter to figure out how much is needed to top off your pool, and then add 10000 to that number. Hopefully that will be close enough for dosing purposes.
IMPORTANT: You should be running the hose between dumps. If they dump in 5000 gallons and then the water level sits static for long enough, you risk developing a nasty, permanent water ring right at that paused level. If you run the hose between truck loads, and so keep the level moving, you'll minimize this possibility. That won't affect the water meter trick, it'll still work, if you check the meter right before the first time you use the hose and right after the last time you use the hose. Doesn't matter how many times you start and stop the hose in between.
There's a way to use testing to confirm your water volume number, no matter how you calculated it. This is assuming you have a quality test kit, like one of the two we recommend. You can do so with the pH test, or the FC test. It's pretty simple:
pH: Test your pH, record the result. Let's say you get 8.0 as your result. Use our Pool Math app or webpage to calculate how much acid to add, based on the water volume you think you've got, to reduce your pH to your desired target pH level. Let's call that 7.6. So you add the required amount of acid with the pump running. Wait about 30-60 minutes. Then test your pH again. If you get 7.6, then you know you've got a good water volume level. If not, adjust the water volume number accordingly to get the math to work out. Repeat that process several times, over the course of days or weeks, until you fine tune your water volume number such that you get consistent results.
FC: Pretty much the same principal, but you have to try to eliminate a few variables that can affect the process. Do the before and after tests after the sun goes down. This eliminates FC loss due to the sun burning off your chlorine. Don't let anybody in the pool between the tests. That eliminates FC loss due to swimmer-load. Be sure your pool is clean and free of organic material (like leaves). Organic material uses up FC, so that can affect the results. And be sure your pool doesn't have any active algae. You can determine that with an
OCLT. Or do the tests in the winter, when it's unlikely you have any algae and nobody has been swimming in the pool.
You get the idea. The primary reason to know your water volume number is for calculating dosing using Pool Math. If you confirm that you're getting the expected results from dosing, then your water volume number is good.
