I have a cracked Hayward DE model 3600 pool filter. Is there a upgrade replacement without changing plumbing?

It's what poppajoe said, but maybe I can make it a bit more clear. The backwash valve is separate from the filter - so there are standard connectors and standard connector spacing for backwash valves. There should be plenty of new filters available that will connect on to your existing backwash valve in place of your current filter with no changes to the plumbing. And the valves have unions on then so no need to cut, glue, or anything like that.