Not entirely accurate. "Checking fuel" for contamination and sump draining are maintenance functions at the major airlines.

I was a Line Maintenance Crew Chief for a major airline for 20+ years and one of the things we did on each line check (overnight checks) was to sump the aircraft fuel tanks. We did this early in the morning after the aircraft had been parked all night. I had our crew do it just prior to the fuel truck showing up to allow maximum time for settlement.

And yes, I did it on the 747, DC-10, 727, 757, A-319/320, etc..

It was not uncommon to get a gallon or more water out of each tank (especially the 747's). And yes, I have seen a sump drain get stuck open and dump thousands of pounds of fuel on the ramp. It was usually something like a rivet or small chunk of sealant that was the cause. Some FOD left over from the last HMV with tank repairs and a poor cleanup job.