Friday it rained like crazy here in the DFW area. When I got home pool was almost full. Didn't want it to overflow so I decided to backwash the filter to lower the water level. I do not have multiport, just a slide valve. I backwashed the filter about five times, four to five minutes at a time, before the level was down to an acceptable level. I know this is more than is recommended. I recharged the filter with DE. No DE was returned to the pool and the pressure after backwashing is just a bit above my clean pressure. Is it possible I may have damaged the grids by doing this? If one does not have a multiport, is this an acceptable way to lower the water level?