Im about to clean my Hayward DE filter and clean it.
Once cleaned and put back together, does the pressure gauge automatically "reset"?
Im assuming yes but would rather know for certain before I get myself into a mess.
Your pressure gauge should zero once the system is depressurized. When you refill the filter and begin running again, you may notice that the pressure gauge does not read 'exactly' the same as it did the last time you started fresh (but, it should be close).
When you're cleaning the DE from the filter housing, remember to clear the port going to the pressure gauge as well.
Clean it all, reassemble it, bleed out any trapped air -- there will be a bunch -- and recharge it with fresh DE. See if any more air bleeds out, and then you can see what your clean pressure is. If you have the outer ring, you have to move it around.