Ding a bit of research, and came across this
The Four C Trail is a really easy trail to hike, with one issue. You need to supply your own water. The ponds and streams aren't safe to drink from even if you boil it. The water is contaminated with low levels of heavy metals and even filtering doesn't pull those out. In an immergency you'd probably be okay, but guzzeling liters of it is a bad idea. To hike the trail in cool weather you probably still need at least four liters of water along to drink and cook. More if you need to wash dishes. Now, that's a lot of weight to haul up and down hills. Luckily it is really easy to stash bottles of water along your path. The Four C Trail crosses several roads that connect the different trailheads so as you just stop the car, hop out and cache water near the trail/road intersection.
Road Crossings: CR 511-3, FS 526, FS 512, NF 517, CR 1175, Big Slough Wilderness Road, CR 1170, FS 536, HW 227, FS 521-E
If you want to stash water halfway (near the Walnut Creek Campsite) leave your water just off FS 511-2. It's about 1/2 mile from the campsite.
He hikes the same basic route we're talking about, starting at the north end:
We started hiking from the north end and it took about four hours to get to the Walnut Creek campsite. This did include losing the trail twice. The first time the trail was following a logging road then takes a sharp right turn into the woods after crossing a bridge. The white trail blaze was gone so we continued walking to the end of the logging road. Grrr. Backtracking eventually got us back of track. A similar thing happened the second time. Several blazes were removed which lead us to wander some until we stumbled across a bridge on the trail. Basically, keep an eye on the map/gps.
He says that Pond Camp is small with no facilities, but didn't stop. He gives a good description of Walnut Creek Camp but, IIRC, its closed.
Guess I'll strap on the 2 qt canteens.