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The Shower Mixing Valve

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Traditional two-handle hot/cold valves are no longer acceptable in a custom shower system because they are unsafe. Even a sudden, minor temperature fluctuation creates thermal shock that might cause you to move and slip on the shower floor. A major fluctuation might actually cause scalding.

There are two main technologies avaialble today that reduce the risk of thermal shock, Thermostatic and Pressure-balanced.

The Pressure Balancing Valve

The pressure balancing valve automatically adjusts outgoing water flows of hot and cold water by balancing the pressures between the incoming hot and cold water supply lines, keeping the temperature of your shower within safe limits. Pressure balancing valves generally deliver less water flow than thermostatic valves. Most deliver about 5 gallons per minute at 80 PSI, enough to service at least two showerheads, using 2.5 gallons per minute (9.5 liters per minute), when they are turned on at the same time.

The Thermostatic Shower Valve

Thermostatic valves use technology that senses water temperature and automatically adjusts shower temperature to the level you select. Thermostatic valves come in larger sizes and are able to serve more shower outlets concurrently. And, because the thermostatic element restricts the flow of cold water on start-up, you won’t have to wait as long for the shower temperature to reach the level that feels comfortable to you.

Thermostatic valves range in delivery flows from about 12 to over 20 gallons per minute. They are the valve of choice when columns of body sprays are specified. They are also useful in tub applications where a handshower or showerhead are also used because they can fill the tub quickly and offer scald protection when using the showerhead or handshower.

Electronic Valves

These valves are quite new for shower systems and are just gaining acceptance. They are very popular in high-end custom shower systems. Kohler offers the DTV, which offers a control panel to operate up to six different outlets. These systems often allow you to program them with temperature and outlet preferences so you can call up your favorite shower with a simple preset.

Pressure Boosters

See our section on water pressure.

Step by step process to a shower system design

1. Determine which shower fittings – including showerheads, handshowers, body sprays and tub fillers – are desired, and how many will be on at one time

2. Determine the total maximum water usage. Consider if the flow regulators will be removed

3. Determine the water pressure available

4. Select a mixing valve that will deliver the required water volume. Two valves or a pressure booster may be required

5. Add volume control valves to control the volume of water to individual outlets. Diverter valves may be added to switch between different outlets and may allow shut-off control.

6. Consider adding a steam unit for a combination shower/ steam bath.

7. Ensure the drain is large enough to accommodate the maximum water usage

8. Useful links to resources on the Internet