Chizer & Bunoi 67 gallon

[midgetwaiter]

Originally Posted by sphelps

First it is constant unless your pump is fluctuating which it shouldn't be and second volume has nothing to do with static head pressure.

Possibly I am using the term "Static Head " incorrectly, I'm more a wrench bender than an engineer. However I can show that the height of the water above the drain determines the velocity of the water draining by applying Bernoulli's Principle. There's all sorts of handy calculators on the web that help figure this out, like this:

http://www.efunda.com/formulae/fluids/draining_tank.cfm

It has been my experience that this increase in velocity makes adjusting a gate or ball valve on the drain MUCH easier. Determining the reason for this goes well beyond my math skills but it's very easy to demonstrate. I think it's because you end up with a full pipe before the drain valve which ends up giving you a more even flow rate. Regardless it translates into easy, repeatable and reliable adjustments.