Shower Manual Valve Design

I have an initial hand-drawn concept for a new manual valve that will sit behind a residential shower trim plate. The idea is simple: give the user precise flow control while all but eliminating the chance of hidden leaks. What I need now is an engineer or product designer who can turn that sketch into a complete, production-ready solution. The core requirements are clear: • Manual valve system only – no thermostatic or digital electronics involved. • Components to be moulded in plastic; material selection should balance cost, durability, and resistance to hot, chlorinated water. • Primary function is flow control; temperature balancing will be handled upstream. • Leak-prevention is critical, so gasket selection, seal geometry, and any weep holes or moisture indicators you recommend should be addressed in the design package. I will provide the sketch, dimensional constraints from the existing rough-in cavity, and a short list of competitive products for reference. From you I’m expecting a full CAD model (SolidWorks or similar), exploded views with part numbers, a concise Bill of Materials, and any FEA or flow-rate simulations you feel are necessary to validate the design under typical home water pressures. If you have hands-on experience with shower cartridges, O-ring groove standards, NSF-compliant plastics, or have taken a plumbing fixture all the way to tooling, your insight will be invaluable. Let’s make a tight, reliable valve that installers and homeowners will trust for years.