I have a mesh cover so I almost always have to SLAM when I open... Second day of SLAM, the water is clear enough to see the debris on the bottom, so I proceed to vacuum to waste. I get my filter online and start filtering. After about 24 hours, the pressure climbs by about 6psi so it's time to backwash. I backwash, rinse, backwash, rinse a few times and replace 4 scoops of DE. The pump starts making a very strange sound so I go to check my pressure gauge. I am expecting 18PSI but it's reading about 5PSI and I see no swirling inside the pump. I ALMOST went back inside thinking "It will work itself out..." but then I shut off the pump, took off the lid, and what I saw inside was a basket completely full of pine needles with about 3lbs of DE mud sitting inside.. no wonder there was no pressure! I pulled out the pump basket, took it over to my skimmer, and dumped it into the skimmer basket to save the DE, gave it a good cleaning, replaced the basket and cover and air bled, and back to normal operation. Had I just walked away for a few hours I might have burned up my pump.
Lessons Learned:
1. When you vaccum to waste, its only bypassing your filter, NOT your pump basket
2. When it's time to backwash your DE filter, your pump basket probably also needs a good cleaning FIRST.
Anyway, I thought I would post this just in case any of you have a similar issue. It was NOT obvious to me at first what was going wrong, and I somehow got it in my head that vacuuming to waste bypasses the pump basket. It does NOT!
Lessons Learned:
1. When you vaccum to waste, its only bypassing your filter, NOT your pump basket
2. When it's time to backwash your DE filter, your pump basket probably also needs a good cleaning FIRST.
Anyway, I thought I would post this just in case any of you have a similar issue. It was NOT obvious to me at first what was going wrong, and I somehow got it in my head that vacuuming to waste bypasses the pump basket. It does NOT!
Heading off potential problems for others in advance, one post at a time, nice. 
