Toilet bowl and seat shape, fixture mounting, and flushing type are some of the options to take into consideration when selecting water closets for a client.
by Siddharth Bhat, PE, LEED AP
The plumbing fixtures known as water closets are present in all types of buildings, and a large variety of selections is available in the market. Water closets can be categorized into various types depending on the design parameters involved, but not everyone is aware of the different types of water closets and how they should be selected. Thus, the following article provides plumbing designers with insight on the types of water closets present in the market as well as guidelines to selecting them depending on the application.
Toilet Bowls
Toilet bowls for water closets typically come in one of two shapes: round or elongated. Other shapes of toilet bowls are available in the market, such as D-shape or square shape, but these are mainly specialty items for aesthetic purposes. Round and elongated bowls account for the majority of fixtures.
Round bowls, as the name suggests, are round in shape, while elongated bowls are oval in shape. The elongated bowl extends 2 inches farther than the round bowl, thus increasing the target area for the fixture. Target area is the open area for the elimination of wastes in the water closet; thus, a larger target area prevents the bowl from being contaminated.
The elongated bowl is usually specified in commercial facilities and public restrooms where usage by a large number of people is expected over a period of time. Elongated bowls also look more aesthetic than round bowls, making them even more suitable for commercial installation. Since usage of a water closet in a commercial setting typically would be high, elongated bowls help maintain hygiene levels around the space. Round bowls tend to be a bit cheaper, although there may not be a significant cost difference now as in the past. However, one of the benefits of round bowl water closets, especially in residential restrooms, is that they allow for a bit more space in front of the fixture due to their smaller size.
Toilet Seats
Toilet seats come in various forms, from the shape of the seat to the load-withstanding capacity of the seat. In terms of the shape, the seat can be an open front or a closed front. In an open front seat, there is an opening near the lip as indicated in the graphic. Having an opening prevents the toilet seat from being contaminated, especially during urination. Initially, open-front seats were developed for women to allow them to wipe the perineal area after using the water closet without coming into contact with the seat. This also prevents genital contact with the seat. The Uniform Plumbing Code (UPC) requires open-front seats in public restrooms since they are used by lot of people, posing risk to user hygiene.
When selecting a seat, another important parameter to be taken into consideration is the load-carrying capacity of the seat. Seats are mainly available as heavy duty or extra heavy duty. As the name suggests, extra heavy-duty seats can carry more load than heavy-duty seats. If heavy, rough use of the water closet is expected, such as in large stadiums and auditoriums, it is a good idea to specify extra heavy-duty seats.
Fixture Mounting
Water closets can be installed in a number of ways based on mounting: floor mount or wall mount. They are further divided into floor-mount bottom discharge, floor-mount wall discharge, and wall-mount wall discharge. The selection of a specific type of fixture mounting depends completely on the owner’s preference, but designers can provide some pointers on the pros and cons of each type.
A wall-mounted water closet is mounted on the wall via a carrier that is mounted on the chase. One of the benefits of these water closets is that unlike floor-mounted water closets, wall-mounted water closets can be shifted from an ADA height to a non-ADA height just by modifying the elevation of the carrier and the associated drainage pipe in the wall instead of buying a completely new fixture. Also, having the fixture wall mounted allows for easy cleaning of the floor under the water closet by the janitorial staff, thus contributing to the overall hygiene of the space.
One of the major concerns owners typically have with wall-mounted water closets is that the carriers and, in effect, the water closets may loosen and become shaky over time. Having wall-mounted water closets also increases the size of the chase needed to accommodate the carrier installation, which needs to be coordinated with the architect during design.
Floor-mounted water closets do not present the design concerns mentioned above. However, with floor-mounted water closets, you may have to specify different units for ADA and non-ADA requirements since these requirements are based on the actual height of the unit rather than the elevation of the carrier as with wall-mounted fixtures. However, some owners may not like floor-mounted water closets since it may be difficult to clean the floor area around these fixtures.
Flushing Accessories
Depending on the type of flushing action, water closet systems may be divided into gravity flush tank, flushometer tank, and flushometer valve. Gravity flush tanks are mainly selected for residential units where usage is relatively low. In this type of system, water is stored in the tank, and when the user flushes, water is let into the bowl. The gravitational force of the stored water in the tank is used to flush the contents out of the bowl. One of the benefits of a flush tank is that unlike a flush valve, it does not have high pressure requirements, thus reducing the possibility of needing a booster system for the facility.
Flush valves are mainly selected for public restrooms and commercial facilities where simultaneous use of fixtures is likely to occur. A flush valve uses water pressure directly from the water line connecting to it to flush the water closet. Each of the flush valves has minimum incoming pressure requirements based on the manufacturer’s specifications, which need to be taken into account while designing the water system for a facility. One of the major benefits of this system in a commercial or public restroom is that unlike a flush tank, the user does not have to wait for the tank to fill up before he flushes, thus significantly reducing toilet usage time. Flush valves typically use more water than flush tanks. Also, flush valves mix air with water to achieve more pressure while flushing, so they may provide a cleaner water closet bowl.
Flush valves can also be categorized by the installation location: exposed or concealed. Like the name suggests, the entire assembly of a concealed flush valve is concealed, with only the flushometer button/sensor exposed. Some owners may prefer this due to aesthetic reasons. Some facilities such as correctional, behavioral, and healthcare may request concealed flush valves to prevent exposed flush valves from being used for harming oneself.
Flush valves also can be manual or sensor operated. Sensor-operated flush valves provide more hygiene since users are not required to touch the flush valve. Due to the recent pandemic, a lot of owners have opted for sensor-type flush valves to promote more hygienic restroom conditions. Sensor-type valves may be hardwired or battery powered. Using battery power can prevent additional costs for electrical connections during building construction; however, using battery-powered sensors means that maintenance staff would have to replace the batteries from time to time. However, manufacturers have been increasing battery life to last for three to five years before replacement is required.
Other Options
Other water closet features vary based on the type of facility. For instance, in a correctional facility the owner may opt for stainless-steel, anti-ligature, vandal-resistant fixtures, while in a commercial facility the owner may opt for vitreous china since the aesthetics of the fixtures is a major concern.
After reviewing all of the available options, the designer should consult with the owner and take their preferences into consideration while making a selection.
About the Author
Siddharth Bhat, PE, LEED AP, is a Mechanical and Plumbing Engineer at DLZ Corporation with specialization in correctional facility design.
The opinions expressed in this article are those of the author and not the American Society of Plumbing Engineers.
