If I understand you correctly, you just have to make sure your sump will handle that 2 inches of water until the output of your plumbing breaks the siphon. You can guestemate it by using the handy old tank capacity calculator. If your tank is 36x12 (standard foot print for a 33 gallon) and your plumbing ends two inches below the water surface, simply multiply the 36x12 (tank foot print) x 2 (water depth) then divide that by 231. That means your sump would have to handle about 4 gallons of water. That's a very rough estimate though. Like I said, test it and make sure the sump can handle it, and adjust as needed.
Doug
|