Linear Drain System Specification 101 for Accessible Bathrooms and Wet Rooms

Streamlined shower design feature offers sophistication and sanitation
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Sponsored by Infinity Drain
By Kathy Price-Robinson

Modern Waterproofing Techniques

Modern waterproofing techniques are normally performed by the tile trade and fall into two types: liquid membrane and fabric sheet/membrane.

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Liquid membrane waterproofing techniques can be used to create benches in the shower.

Liquid membrane is a paint-on material that has the consistency of yogurt. It dries into a hardened, rubberized membrane that can fit any shape shower enclosure and can be used on benches, niches, and into the “dry” area of the bathroom (outside the area dedicated to the shower) to easily create a wet room (where the whole room is waterproofed).

Fabric membrane waterproofing uses a non-woven fleece fabric. It is applied to the sloped mortar bed using thinset. Cove and corner pieces are used to waterproof the entire shower enclosure. This can also be used as a vapor barrier if the shower contains a steam unit.

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Shown is a fixed-flange installation.

A fixed-flange installation uses a liquid membrane waterproofing. Instead of the sandwich of traditional waterproofing, this could be thought of as an open-face sandwich. It includes one mortar layer, waterproofing, thinset, and then tile.

Note that the channel shape is different than site-sizable or fixed-length drain and has a 1-inch flange on all four sides. Instead of tiling to the side of the channel as would be done with traditional waterproofing, tile is applied directly on top over the channel flange. Waterproofing is either painted on to the flange edge or fabric is glued to the edge to make the shower watertight. Thus, there is no waterproofing membrane to clamp onto, so a coupling is used to connect the channel outlet to the waste line.

Complete Shower Systems

Finally, under the umbrella of modern waterproofing is the newest innovation in shower construction: a complete shower system. This takes guesswork out of shower construction and saves time and labor at the job site.

A complete shower system includes a linear drain, a pre-sloped shower floor, and wall board. There may also be accessories such as benches and niches available as part of the system. The wall board and pre-sloped shower floor may be pre-faced with fabric or liquid waterproofing, or the waterproofing may need to be applied on-site depending on the manufacturer.

These types of complete showers usually come with a system warranty, which gives homeowners, installers, and specifiers a level of protection.

Considering Flow Rate

Flow rates of the specified shower fixtures need to be calculated early in the planning phase. The linear drain must be able to handle the combined flow rate of the fixtures installed in the shower. For example, a shower may include a rain head, hand-held, and traditional shower head, each with a flow rate of 2.5 gallons per minute. Standard linear drains can generally handle up to 9 gallons of water per minute and connect to a 2-inch waste line. High-flow versions that connect to a 3-inch waste line will accommodate a flow rate of 21 gallons of water per minute.

Latest Advances: Stainless Steel Shower Bases

One of the latest advances at the forefront of architectural and decorative drains is specification of a stainless steel shower base. This is seen by some as a game-changing option for shower installation. Look for a manufacturer that guarantees for life against waterproofing failure so that if the product should develop a leak, the manufacturer will bear the cost of labor, removal, and replacement, and will restore the installation with the same ‘like and kind’ materials originally used.

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A stainless steel shower base is a game changer for some in the plumbing business.

Stainless steel shower bases are an example of “innovative, customizable solutions that makes shower installation a far more seamless experience,” says Infinity Drain President Jonathan Brill. “As waterproofing methods continue to evolve from traditional to more time-saving approaches that eliminate steps in the process, we are reflecting that change in the products we develop.”

Stainless steel shower bases also dramatically reduce the amount of time required to install a new bathroom shower and decrease the need for coordination between several trades. Because it is ready to tile, pre-sloped, and does not require additional waterproofing on the walls, it eliminates many time-consuming steps that traditional methods require.

Depending on the manufacturer, stainless steel shower bases include a curb or curbless option and the ability to use any grate style or tile insert.

Where to Place the Linear Drain System

The most popular linear drain placement is along the back wall. If the shower has a curb, you can essentially place the drain along any side since there is a physical barrier between the dry and wet side of the bathroom.

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The most popular placement for a linear drain is along the back wall of the shower enclosure.

When removing a tub to create a large shower enclosure, site-specific conditions may require that the linear drain is placed along the wall with the shower fixtures. This is most likely where the tub drain was located. Depending on which way floor joists are running, the waste line may be able to be relocated closer to the finished wall.

Placing the drain along the threshold of the shower is popular for barrier-free or curbless showers. For this installation, a wall-to-wall fit is critical to keep water from traveling to the dry side of the bathroom. With this placement, it is always recommended that the dry side of the bathroom be waterproofed and pitched slightly toward the linear drain.

For a true wet room, which will be discussed in more detail later in the course, the entire bathroom is waterproofed and sloped toward the drain.


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Originally published in June 2020