Shower Pressure Adjustment

Can shower pressure and temperature generally be adjusted in the wall? I have an old Delta shower handle whose pressure is lower than everything else in my house. the plumbing to it looks good, I've installed new pipes for another bathroom being installed and an outside faucet and they have great pressure too (not run off the same lines as the bathroom in question.) I'm a novice on this and cannot figure out if these can be adjusted or if I need to look at toward another angle. thank you, Roger

What are the pipes made of? If there is any galvanized at or near the shower, that could easily be a problem. Generally, the shower valve has more capacity than the restrictors mandated by the feds on new showerheads. A showerhead bought in the last several years is restricted to 2.5 gallons/minute. Depending on the pressure you have, and the quality of the head, many people find them less than great.

Sometimes, the valves have debris screens that can get clogged. Same with the showerhead. Sometimes, all it takes is cleaning the screens.