I always tee (or technically "cross") presoak, tire cleaner, and air into one check valve and tee the tubing lines in the room. It's simpler with one less check valve to go bad and it will work the same in the bay. This is how I like the manifold:
The long nipple under the central cross is stainless steel. After 20 years of high pressure and chemical flow, a brass nipple will get really thin. When it breaks, you'll have a lot of trouble getting it apart with standard pipe extractors.