Learn what factors need to be considered depending on the type of use and environmental conditions in nearby areas.
by Siddharth Bhat, PE, CPD, GPD, LEED AP, WELL AP
Floor drains are the most commonly used mode of drainage in buildings. The ubiquitous nature of this plumbing fixture makes it susceptible to negligence; hence, it is important to understand the options that are available to ensure proper performance.
Floor Drain Capacity
The basic function of a floor drain is to drain any fluids and residue effectively in the least possible time. This is where drain capacity becomes critical. An undersized drain may lead to water not being drained at a desired pace, causing an accumulation of water in the area or even splashing in the area around the drain, especially if water is released at a high flow rate such as with a clothes washer.
Drains requiring higher capacity are typically larger in size. It is critical to coordinate the expected flow in an area with the drain manufacturer prior to installation.
Another critical item is the depth of the floor drain. If the floor drain is too shallow, the water, especially if discharged at high speed, may hit the bottom of the drain body and spill out. This may even take place if the drain is sized sufficiently for the flow.
Floor Drain Shape
Floor drains are available in a variety of shapes. The most commonly available shapes are round, rectangle, and square. Some manufacturers may also provide customized shapes at a premium.
When selecting the floor drain shape, it’s critical to coordinate with the architect. Sometimes rectangular drains may be preferred where floor tiles are used so the drain can easily blend into the surroundings by matching the tile size rather than cutting through it.
Load Rating
The load rating of a floor drain is the maximum load the unit can withstand prior to failure. Floor drains are typically located in spaces where you can expect pedestrian and vehicular traffic. If the floor drain is not selected for the right type of load rating, it can fail prematurely.
The three common categories of load rating are light duty, medium duty, and heavy duty. Heavy-duty floor drains typically can withstand loads up to 8,000 pounds. Medium-duty and light-duty floor drains typically can withstand loads up to 5,000 pounds and 2,000 pounds respectively. This may vary from manufacturer to manufacturer and from product to product, so it is critical to coordinate with manufacturer specifications.
Floor Drain Material
The most commonly used materials for floor drains are cast iron and stainless steel. Cast iron is typically used in noncorrosive environments, while stainless steel is used in corrosive environments. Stainless steel floor drains are more costly than cast iron floor drains.
Stainless steel floor drains are made of Type 304 and Type 316. The main difference is that Type 316 contains molybdenum, while Type 304 does not. Molybdenum makes the drain more resistant to chlorine-based and saline environments.
Strainer Material
Strainers are available in numerous materials including bronze, cast iron, chrome plated, nickel bronze, and stainless steel. Nickel bronze is the most commonly used strainer material as it provides an aesthetic finish and is easy to clean.
Other Features to Consider
ADA and Heel-Proof Grates
The slots or openings in grates are critical to consider when selecting floor drains. For instance, if high-heel foot traffic is expected over the drain or if the drain must be Americans with Disabilities Act (ADA) compliant, you will need to select products accordingly. These units typically have smaller grate openings so heels or wheelchair wheels do not get stuck. These features are typically indicated on the manufacturer’s specifications.
Flushing
Some types of drains contain flushing rims. They are specified in areas such as hospitals or morgues where you could expect hazardous waste such as blood that may accumulate in gaps around the drain and solidify. If there is not an effective way to clean the drain, bacteria would accumulate, leading to unhygienic conditions. Hence, flushing rims are required.
Sometimes the drain is connected to the flushometer valve of a urinal or water closet, which sends water through the drain anytime the flushometer valve is activated, thus ensuring periodic cleaning.
Vandal-Proof Grates
If a floor drain is located in an area that may be subject to vandalism, it is critical to provide vandal-proof grates in these situations.
Security Fasteners
These are typically provided for floor drains in high-security and healthcare settings. Security fasteners ensure that the floor drains are tightly secured to the floor, so the risk of tampering or suicide is reduced.
Trap Protection
Trap protection is primarily provided in two forms. One is known as trap primer protection, while the other is in the form of trap seals. If a trap primer is used as the mode of seal protection, you need to ensure that floor drains are provided with a trap primer connection. If trap seals are selected, you need to ensure that they are ASSE certified.
Adjustable vs. Nonadjustable Tops
Floor drains come with adjustable and nonadjustable tops. Adjustable tops are typically preferred since they make it easier to level the floor drain with the adjacent floor.
Securing Flange
Securing flanges are provided as additional protection against accidental spills around the floor drain. The flange extends beyond the floor drain and allows the spilled fluid to drip through the weep holes to the interior of the drain, thus preventing fluid accumulating on the floor.
In conclusion, many factors need to be considered when selecting a floor drain that depend on the type of use and environmental conditions in nearby areas.
About the Author
Siddharth Bhat, PE, CPD, GPD, LEED AP, WELL AP, is a Mechanical and Plumbing Engineer 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.
