Cindy and I visited Zion National Park in late September and stayed in our TM 3124KB at the Watchman Electric Campgrounds located near the Park Visitor's Center. As noted in the campground name, this campground has electricity but does not have city water or sewer on the RV sites. Potable water is located at the dump station near the campground entrance. The ater spigots near the restrooms don't have threaded connections for hoses, that's why you need to use the potable water at the dump station. RV campers should fill their fresh water tanks before proceeding to their specific campsite. Most of the RV sites are shaded in this particular campground. These campgrounds must be reserved during the prime season (through October) at least several weeks in advance.
I tried to return to the same campground a couple of weeks later and there were no campsites available and I had to use the Ferber Resort (
http://www.zioncamp.com/) at the Quality Inn just outside the Park. This RV Park has full connections to include Cable TV for $27 a night. There are other RV parks between Zion and the town of La Verkin, Utah. Zion River Resort RV Park and Campground (
http://www.zionriverresort.com/) is the newest and more expensive.
Below are some photos of some of the lesser known sites at Zion. You can see pics of Zion famous sites by viewing Google Images of Zion National Park.