Our Dealer told us to take the filters out twice a month and rise them out with a water hose real good, then every 3 months or so, when we drain to clean, to put the filters in the dishwasher with no soap.

Whats your thoughts on putting the filters in the dishwasher? Would it tear up the filter?

Hosing them off when the filter pressure goes up by about 6 is all you should need to do during the pool season, unless the filter is way undersized. There is no point in cleaning them more often than that. That might be anywhere from weekly to once a season, depending on the size of your filter. Then about once a year you should soak them in a mixture of automatic dishwasher detergent (one cup for every 5 gallons of water) overnight and then rinse throughly before replacing in the filter.

I don't see how the dishwasher could damage a filter cartridge, if it fits, but I don't see how it would help either.

Unfortunately, on most hot tubs, there is no pressure gauge. So we're relegated to cleaning on a regular pattern. If your system is pressurized and has a pressure gauge, then you could certainly go that route as well.

I've seen some of these newer tub filters being made out of polymer and the dishwasher being the standard way of cleaning them.

But, if they are standard fiber cartridge filters, then I'd suggest you rinse them with a hose every couple of weeks and soak them with a good cartridge filter cleaner (see your dealer or online hot tub chemical store) when you do water changes. I rotate 2 sets of filters so I can put a clean set in as soon as I fill the tub up. Then I soak, rinse, and store my dirty set. Always worked well for me.

Is what your dealer recommended wrong? Hard to say. Maybe he wants you to tear up filters faster so you come in to buy more? You could contact the manufacturer and ask how they recommend doing it...