never even tried to stop it myself , i would usually keep about 50 gallons in it ,and when i left a job i would dump any access if i had to travel any distance .
These are baffle balls. They use up about 2 - 3 % of the total volume in a tank. They are 15" diameter assembled, but can be bent to fit through a smaller opening and assembled inside the tank. Multiply your tank volume by .105 for the required number of balls. $9.00 each.
I heard the black pvc drain pipe stuff works, but I like the baffle balls better myself. So I will be ordering a few of those. Since, I just got a big o' 300 gallon water tank for 100 bucks. ""chuckle"
Here is another style baffle ball. These snap together as 2 halves, but HAVE to have a 16" hole to get them through. Multiplier on these is .075 / gallon. They are $10.25 each.