Creating a Custom Shower

Showers can be simple, showers can be luxurious. You'll come out clean either way, but as with many things in life, the journey is just as important as the destination. Those that crave personalization and/or indulgence live in fortunate times: the options for custom, multi-outlet shower installations are greater than ever. While conservation measures can put a damper on the most fanciful designs, most find that today's water-efficient shower heads actually are capable of creating a lavish experience without the waste.

There are a number of things to take into account when designing your system, as well as some preliminary concerns that need to be addressed before you get too far in. So if you're ready for a custom shower, here's some helpful information to get you started!

Code Restrictions

Federal law limits the total output of any shower system to 2.5 gpm, regardless of the number of heads/outlets. Some states, counties or cities may go even further: the California Plumbing Code states that showers can use only 2.0 gpm at any given time (this max flow rate will be reduced to 1.8 gpm in 2018). While this does prohibit the "car wash" systems of some dreams, multi-outlet systems with low-flow heads can be installed that are capable of providing surprisingly effective simultaneous sprays. However, most systems that meet such strict criteria have diverter valves that allow only one outlet to be active at a time. Be sure to check with your local code authority before proceeding.

Water Pressure

Do you know your home's water pressure? A system with 3+ outlets needs a minimum pressure of 50 psi to perform adequately. If your pressure is low, you'll need to look into a booster pump for the house.
If you're on well water, be sure that the pump and pressure tank will be able to keep up with the large demand a custom shower can create. Adjustments may need to be made to the float switch, or the pressure tank or pump itself may need to be upgraded. Discuss your plans with your plumber or well service.

Hot Water Supply

Although today's multi-outlet systems are limited to 2.5 gpm total output, older systems could put a strain on what used to be a sufficiently-sized water heater. To get an idea of the ideal hot water capacity for a given system, multiply the system's flow rate (the gpm of each outlet that's active) by your average shower length. This isn't exact - you won't only be using hot water - but it's actually pretty close: remember that water heaters have a tank capacity as well as a useable capacity that's around 70% of the tank capacity. So a 50 gallon tank will only have around 35 gallons of hot water available at a given time. If you're near that 70% mark, you might consider upgrading - even if you don't deplete the tank, less hot water will be available for other things while the water heater recovers.
How high you have the water heater temperature set also plays a role in how long a shower can be taken. The higher the initial temperature, the more cold water required to get it down to a nice shower temperature. While this will clearly increase your energy use, it will also give you a few more minutes of heat!
A tankless water heater (especially one dedicated to the shower) could be a solution to inadequate hot water supply, but do come with their own set of concerns. Modifications to the electric/gas supply and ventilation may be required. Be aware that things can get pricey with tankless.

Drainage

With federal regulations classifying even multi-outlet shower systems as a single showerhead, you shouldn't have to worry too much about drainage - only 2.5 gpm (or less) should be flowing down the drain at any given time!
Older multi-outlet, multi-flow systems could be sending upwards of 15 gpm to the drain - in which case a standard 2" shower drain won't suffice. A second drain - or a 3" version - may be required to avoid flooding the bathroom. And it's not just the size of the hole in the floor - ensure that drain piping is sufficient all the way down.
On a septic system? With older high-output systems, you may encounter issues with both the tank and the leach field from too much water discharge.

It's only after you know what's (legally) doable in your particular circumstance that you should start planning out the actual shower experience; putting cart in front of horse often leads to disappointment. The first thing you'll need to figure out is how many outlets or showerheads you want, and what valve will satisfy that; then figure out where everything is going to go!

The Valve

For convenience and safety, the valve must be a thermostatic or pressure-balancing mixing valve. These valves mix cold and hot water to a set temperature, which is maintained throughout the duration of the shower. Each outlet receives the same temperature water.
As mentioned above, federal law limits the maximum output of any shower system to 2.5 gpm at a time. This makes valve selection much simpler; prior to this clarification, each outlet could put out 2.5 gpm simultaneously, requiring you to have a valve capable of accommodating so much water. Most multi-outlet shower systems can be supplied with standard 1/2" pipes and controlled by a 1/2" valve.
For systems putting out 10+ gpm, the actual water supply lines should be 3/4". It's entirely possible to supply a 3/4" valve with standard 1/2" hot and cold pipes; you will get more water than out of a 1/2" valve, but the output will be diminished and probably lead to poor performance.
In the event you're allowed to go beyond the 13-16 gpm limit of a standard 3/4" valve (i.e. a car wash shower), you'll need to install a second valve. In this situation, it's highly recommended that your hot and cold water supplies be increased to 1" or larger to provide the necessary flow, or that dedicated 3/4" lines be plumbed directly to the valve from the home's main hot and cold water lines.

Outlet Placement

Placement of the outlets is of course up to the user(s). An important question to ask is: where do you want to stand when you shower? Some like to be closer to the wall, while others insist on being dead-center or far away. Consider your water pressure, as well as the force and coverage of the various sprays you'll be using. In standard showers, the average standing distance from the wall is 24-30 inches.
A standard shower head is ideally installed just above the height of the tallest regular user, but still within reach of the shortest adult or older child, should they want to adjust it or change spray patterns.
Rainshower heads have become highly popular for the "main" showerhead, often in conjunction with a handshower to make up for the limitations of the (typically) unadjustable, straight-flowing rainshower. For some, this simple setup can be the extent of their custom shower; for others, it's not a shower without body sprays.
If you're looking for a more personalized alternative to a standard or rainshower head, consider installing a handshower on a height-adjustable slide or wall bar. When mounted on the bar, the handshower acts just as a standard showerhead and can easily be moved up or down depending on the user. This setup is particularly helpful for children and those with limited mobility.
Body sprays are usually located at three levels: shoulders/upper back, waist/lower back, and thigh or knee height. For the best experience, it's recommended that the sprays not be on the same wall or spray the same direction as the showerhead. This falls in line with most people's preference to have sprays at the side or rear.
Planning on using a seat or bench in the shower? Take that into account when placing the body jets - how often will the seat be used, and do you want a jet hitting you when you're there? Would a separate volume control come in handy?
In cases where there's a big difference in height between regular users of the shower, consider installing a separate volume control for the highest body spray so water isn't wasted shooting over the head of the shortest user.
Most manufacturers of body sprays recommend a pressure balancing loop be used to supply the sprays with water from the mixing valve, as this ensures equal pressure between all of the jets (and so a better experience). Some plumbers will forego this recommendation, viewing it as necessary only when there's a large distance between sprays. Installing a pressure balancing loop will guarantee performance, but does require more time and materials. DIY installation? We recommend consulting with a plumber beforehand!

Controls

Make sure you keep in mind the basics when planning your shower system: water shouldn't aim at the door (no matter how much you trust it), and the valve and volume control should be accessible from just outside the shower (you shouldn't have to be inside to get things started).
The mixing valve is typically placed around average waist height (about 36"), with the volume control(s) located just above. Some valves and pre-made systems feature a combination mixing valve/volume control for a sleek look that takes up less wall space.
The diverter valve (responsible for sending water to the outlets you want it at) is usually found above or below the mixing valve and volume control. When using multiple diverters, it may be advisable to place them next to the spray or group they control.
As with the mixing valve, the volume control valve comes in 1/2" and 3/4" varieties. 1/2" volume controls should be fine for systems subject to low maximum flow rates. 3/4" volume controls are recommended for systems using more than 8 gpm.

Designing a custom shower correctly requires time, attention to detail, and an appreciation of limitations - of the house and its plumbing, as well as those imposed by local code. But it's well worth the effort: few renovations have the immense daily impact of a shower made just for you (and yours)!