Installing Flow Restrictors in Your Shower
Flow restrictors do not make for quite as nice a shower experience as low-flow shower heads, but they get the job of lowering your water heater bill done.
FYI: A flow restrictor just restricts the amount of water that gets through it, increasing the pressure of the flow. It does not aerate the water.
Internal flow restrictors, which are metal or plastic disks with holes in them, are easy to install. Make sure you get one that is the same diameter as your shower's water pipe.
All you need to install a flow restrictor is an adjustable wrench. Unscrew the old shower head. (In case you are wondering, yes, the water in the shower should be turned off.)
Next, run a bar of soap or some liquid soap around the threads of the pipe in the wall. This will make it easier to replace the old shower head.
Now place the internal flow restrictor against the washer in the shower head neck and screw the shower head back on. That's it.
External flow restrictors are usually more effective than the internal ones and are just as easy to install. The only difference is you will see one from the outside since it does not rest inside the shower head and water pipe. Again, remove the old shower head. Put the external flow restrictor between the old shower head and the water pipe and screw the shower head back on. Fun, no?