Canyons are inherently risky. Flash floods occur without notice on sunny days. Technical skills & surrounding topography knowledge required yet does not eliminate risk.
Pumphouse Wash is the headwaters of Oak Creek. The canyon I describe spans 4 miles from FR 237 to the Pumphouse bridge on 89A. Kelly Canyon enters from the east near the top of Pumphouse Wash. James Canyon also enters from the east at the halfway point. James Canyon captures most of the water from an area around and across I-17 that you have likely driven over without knowing. Packed with narrows, pools and several waterfalls James Canyon is awesome but not really in the category of a day hike. The upper section of Pumphouse from James Canyon to FR 237 is wide and low. From James Canyon down to the Pumphouse bridge the canyon is narrow and much higher. Therefore I have split Pumphouse Wash into upper and lower descriptions.
From the parking area head down the steep slope into the canyon. I made it down no problem. The gal behind me slid down on her butt. Once in the wash head back under the bridge and up the canyon. The wash is rocky with mid size boulders from the beginning. Please note this is not an area to be exploring with rain in the forecast. You will find yourself a river ornament if you choose unwisely.
Large smooth finished gray boulders get you thinking about fierce currents in the canyon. Turning the first left bend the noise of 89A gives way to the peaceful wilderness. The going was easy having hiked this canyon after nearly four months with little rain. Usually numerous pools are passed. Some wall to wall requiring a swim. Many have scramble routes to one side or the other. Two pools may require a swim.
I passed several trees wedged in-between the canyon walls. Hopefully this should forewarn those planning a rainy day hike. Keep in mind it doesn't have to be raining in the canyon for a flash flood to occur. If it's raining to the north or east you're in trouble.
A short steep canyon enters from the east near the 1.5 mile mark. Continue on up to the larger and wider canyon coming in from the east which is James Canyon. Here I opt to turn around. You can continue on up Pumphouse, but a 14 foot fall is encountered soon. The only means of getting around is a steep scramble route to the right. It's easier getting up than down in my opinion so keep that in mind. You can also head on up James Canyon which is awesome. Though you'll probably just get into more than expected.
WARNING! Hiking and outdoor related sports can be dangerous. Be responsible and prepare for the trip. Study the area you are entering and plan accordingly. Dress for the current and unexpected weather changes. Take plenty of water. Never go alone. Make an itinerary with your plan(s), route(s), destination(s) and expected return time. Give your itinerary to trusted family and/or friends.