At the beginning of last summer, after backwashing, I did not get the switch firmly back into the filter position. This allowed my pool to drain pretty low, until the water level was below the skimmer, and then the pump was running without water for several hours. I noticed last summer shortly after that my auto pool vacuum would stop running within a short period of time after starting it, and now I can only vacuum with the manual vac for about 15 minutes before I lose so much suction that I'm not doing much good. I can definitely tell the amount of water coming into the pool is not nearly as much after the pump / filter has been running awhile, vacuuming or not. However, if I turn off the pump for a few minutes I get some back, and if I turn it off for an hour or more, the vacuum, skimmer, water coming in, etc., is like it used to be. My filter does not have a pressure gauge, so I can not compare pressure with what it was before last summer; however, I guess I will get a pressure gauge to compare pressure when the pump first comes on to a little later, when I start having issues.