Installing two shower heads in one shower is a great way to create a spa-like feeling in the bath. Frequently called "his and hers" shower heads, these two water sources may be operated independently from one another, or they may operate on the same valve. A common problem of this shower setup, however, is loss of water pressure when both are in use. This problem can be solved, provided you can determine the source of the problem.
Check Your Water Source
In many residential areas, cities supply the water. In some communities, however, wells supply water. The output from a well may be 5 gallons of water a minute -- GPM -- or less. The average shower head uses roughly 5 gallons of water a minute; installing two shower heads would exceed the well's capabilities, resulting in only 2.5 GPM per shower head, which would translate into a loss of pressure. To solve this issue, upgrade your well pump, or add a water storage tank to your home to increase the GPM to a minimum of 10.
Check Your Internal Plumbing Pipe Size
Plumbing pipes come in a multitude of sizes. The water coming into your home may be traveling in a 1-inch or 3/4-inch supply line. When it enters your home, however, this frequently shrinks to 1/2-inch pipes. This drop in size can mean up to a 75 percent loss in pressure and water volume. By upgrading the size of your pipes leading to the bathroom to 3/4 inch, you will increase the pressure at each shower head. To do this, you will also need to upgrade the shower valves to handle 3/4-inch supply as well.
Use a Thermostatic Shower System
There are two types of shower valves: pressure balance valves and thermostatic valves. If the two shower heads run off of the same valve, it is most likely a pressure balance system. This means that the valve will try to keep the pressure even through both shower heads, which may result in a loss of pressure, particularly if both heads are not needed at once. A thermostatic valve has a separate volume control for each shower head. You can increase or decrease the amount of water coming out of each shower head, potentially increasing volume and pressure to each. You can also shut off one shower head when it is not in use, increasing pressure to the remaining head.
Use Low Pressure Shower Heads
Shower heads come in a wide variety of sizes and types. One measure is the GPM of the shower head. Some shower heads, like rain style shower heads, use up to 10 GPM, but have very low water pressure, because the water is meant to simulate rain. Other shower heads have much lower GPM and can operate under higher pressure because the internal size of the shower is tighter. There are also shower heads that are designed just for low pressure showers. They help to concentrate the water by holding it in a small reservoir while pressure builds up behind it, so you see a noticeable difference in flow.