To savesome water while shaving in the shower - I have a "modern"mix valve with no volume control - I got a valve for just before the showerhead at Home Depo. It allows me to cut the water flow as low as I want but not change the temp setting. If you go this route don;t waste your money on the push button type (about 6 bucks), go for the type that has a regular twist knob (around 10 bucks). The push button ones eventually get stuck and are impossible ot repair. I'll guess I saved the cost of the valve in hot water use reduction in under 6 months.