Sand Filter or Cartridge?? Which is better?

[waterbear]

I AM surprised...if you backwash your DE filter until the sight glass is clear, then you know you probably have no DE in it. So you add DE, leaving some "room" in case there is some left, until the pressure is where it's supposed to be...and you're done.

In a perfect world, yes. DE can have a tendancy to "cake" (for want of a better word) on the grids and even if the sight glass looks clear it is possible for there to be quite a bit of DE left in the filter. You add your DE and leave some 'room' but the filter only lost a little of its DE powder. You have now overfilled. Might not show up on the pressure gauge at first. Do this a few times and you now have a MAJOR filter cleaning to do. This scenerio can happen and does. If you have ever had to chip away at the hardened mass of DE that can occur you certainly don't want to do it more than once!

That is why I feel it is better to tear down rather than backwash a DE. You really don't have any control of knowing how much DE is leaving the filter and therefore how much you REALLY need to put back in.
Bumping is really just being lazy, Mixing the DE with the dirt and crud collected and then redepositing it on the grids is NOT the way to give you good filtration. When the filter media is dirty it needs to be cleaned!
Like I said, just my opinion!