I have the Hayward EC50C90 Series D.E. filter (Fiber Clear cellulose charged) and it has a drain on the bottom for cleaning and, well, draining! As it stands now, once or twice a season I have to drain the filter to remove the built-up crud in the bottom, but it makes a big mess if I just open up the plug and flush it out. I'm about to the point where it needs it again, and I would like to do some sort of plumbing of the drain to take the mess away from the pool. My question is, are the threads for the plug NPT and what size male threads would fit it? Thanks in advance!