Is the PEX plumbing causing low water flow in my new shower?

Check the showerhead before you start cutting into the drywall. Modern fixtures are heavily restricted by federal law, ussually to 1.8 or 2.0 gallons per minute, and that low-flow feeling is almost always caused by a plastic **flow restrictor** tucked inside the neck of the showerhead. Take the head off and look into the threaded inlet. You’ll usually see a colored plastic disc with a small hole. Pop that out with a pair of needle-nose pliers and you will likely get all the volume you need without touching the plumbing behind the wall. If that doesn't solve it, your concern about those PEX crimp fittings is valid. Standard PEX-B uses insert fittings that significantly neck down the internal diameter at every junction. If your installer used a series of 90-degree elbows instead of making wide, sweeping bends with the pipe itself, you are dealing with alot of friction loss. It’s essentially creating a series of bottlenecks before the water even reaches the mixing valve. Swapping to copper or even **PEX-A (expansion PEX)** whould improve the flow becasue those systems don't use the thick-walled inserts that sit inside the pipe.

Since you have a plumber coming and access from the back is easy, having them look at the layout is a smart move. If the

I'm in a similar boat and someone mentioned looking at the "scald guard" inside the handle. Is it posible the installer just didn't dial the mixing valve all the way open? Also, if you do end up swapping to copper, maybe ask about ProPress? I'm terrified of torches near old wood and wires too, and those press tools don't need any heat. Seems like a safer bet if you're worried about that electrical conduit.

Check the integral stops on the valve body before you start cutting any pipe. Most modern mixing valves have small screw-shutoffs on the sides that control the flow right at the source. If the installer didn't back them out all the way, you'll get that weak pressure no matter what pipe you use.

Also, look for construction debris. If the lines weren't flushed, PEX shavings or sediment can jam the cartridge or screens. It’s much easier to pull the cartridge and flush it than to repipe the whole wall.

Don't overlook the actual valve brand and model. Some of those budget contractor-grade valves have tiny internal ports that restrict flow no matter what pipe you use. Also, have your plumber check the house PRV (pressure reducing valve) while he's there. If your static pressure is sitting low, like under 45 or 50 psi, those PEX-B fittings are going to feel alot more restrictive than they would at 60 psi. It’s a quick gauge test on a hose bib that’ll tell you if you’re fighting a losing battle with the street pressure before you start ripping out walls.

Check the actual riser pipe from the valve up to the showerhead. If the installer used 1/2-inch PEX-B for that run, the internal diameter is alredy smaller than copper (.485" vs .527"), and those crimp elbows at the top neck it down to about .35". It's a massive choke point right before the water hits the head. Since your plumber is already coming, ask him to swap that specific vertical stretch to a brass nipple or copper. Keeping that last two feet as wide as posible helps with the velocity. Since you have back-side access, it's a quick fix that avoids the main valve mess.