I have installed a water filter on the inlet side, just after the hose reel, in the water bay along with a "on the go" water softener following that. I have a very small water bay but was able to hang the filter and stand the softener just inside it. I use quick disconnects to be able to pull the softener out to recharge it.
This set up works great for security and heat. I do not have any pic's right now, but if you PM me I will send you some next weekend.
1998 MADP 4061