My GT325 is like your set-up - two female hose connectors, one for city water and one for filling the potable tank.
After fruitless searching for a small pressure vessel to force the sanitizing fluid in, I'm in the process of making my own. I got a 24" length of 4" diameter schedule 40 PVC pipe. At both ends, I'm putting adapters that will go down from the 4" size to a garden hose connectors. At the input end, the first adapter is one that takes a screw-in cap.
The plan is to connect the output end to the RV potable water inlet through a short "white" hose, take the cap off the other end and pour in a gallon of bleach. Then I'll put the cap back on, hook a white hose to it and use our city water (about 55 psi) to blow the bleach in and follow it with water to fill the tank to about 75% full of bleach/water solution.
I'll let it sit a while, then drive the rig around to slosh the mixture everywhere in the tank. Afterwards, I'll run the mixture through the various faucets and the toilet. A couple of full tanks of clean water, with a drive around each time, should clear the chlorine smell and we'll be ready for the season.
Had we been able to complete our last trip with Anacortes city water, this rigmarole wouldn't have been necessary, but we had to add water for the last leg home. We got some city water that tasted peculiar.
I'll be curious to see how long the chlorine taste takes to clear. I was thinking originally of using Hydrogen Peroxide, but the cost is much higher than bleach.
Frank and Eileen
No longer RVers or FR owners