What Is a Shower Dam and How Does It Keep Water In?

A shower dam is a flexible, collapsible rubber strip that runs across the open entry of a curb-less shower base and does the job a curb would normally do. On Ella's wheelchair accessible barrier-free bases it ships standard as the collapsible rubber dam, also called a water retainer, flexible shower dam or collapsible threshold. It flattens when a wheelchair or walker rolls over it, springs back once the wheels pass, and keeps the shower water inside the stall. The base it belongs to is described in What is a roll-in shower and how does it work?, and this page covers the dam itself: why it exists, how it works, how it is installed and how it compares with a raised threshold.

Why a Roll-In Shower Needs a Dam

A conventional shower keeps water in with a curb. Ella's one-piece and three-piece shower stalls have a 4 inch threshold, and a 3 inch step-in base is offered for anyone who prefers a slightly raised edge. A roll-in shower is defined by having nothing to step or roll over, and ADA standards generally limit the threshold in a roll-in shower compartment to a maximum of 1/2 inch. Ella's AcrylX barrier-free bases have a beveled roll-in entry of 3/4 inch to 1 1/8 inch depending on size, and the SMC bases are 1 inch or 1 1/8 inch, the lowest entries Ella makes.

With the entry that low, the slope and drainage channels molded into the floor carry water to the drain, but nothing stops water from running out the open side while someone showers. The dam gives the stall the water control of a curb without the curb. The video on this page ends with a demonstration of how well the dam contains water once it is in place.

How the Dam Works

• Material. The dam is a flexible, compressible, waterproof rubber strip. The wheels of a wheelchair, walker or shower chair roll over it while entering or exiting, the material compresses under the wheel, and once the wheel passes it returns to its original shape.
• Mounting. It attaches with strong, water-resistant self-adhesive tape, protected by a red backing that is peeled away during installation. No drilling is involved, and the base threshold must never be drilled, because drilling the threshold voids the base warranty.
• End caps. A plastic end cap is fitted at each end of the strip and sealed with silicone, so water cannot escape at the wall.
• Where it belongs. The dam is made for exclusive use with a barrier-free wheelchair accessible shower base. The low-threshold acrylic and cultured marble bases have a molded threshold instead, so they do not use a dam.

How the Dam Is Installed

The installation is a careful adhesive job rather than a plumbing job, and the video on this page shows each step. In order:

1. Measure the entry precisely.
2. Clean all surfaces thoroughly with alcohol. The video uses denatured alcohol. If the mounting surface is not clean, the adhesive will not bond.
3. Lay a tape line on the floor as a guide for the dam.
4. Measure how much material is needed, mark it and cut carefully.
5. Insert the plastic end cap at each end as indicated and apply silicone to any gaps.
6. Pull the red tape backing away about an inch and set the dam down snugly against the shower wall and floor, then slowly pull the backing away as you work down the length of the dam.
7. Press firmly along the entire length to secure the adhesive.
8. Remove the guide tape, clean all surfaces again and lay painter's tape on both sides of the dam.
9. Run a thin bead of silicone along the lower edge of the dam on both sides and smooth it, making sure both end caps are sealed as well.

Two rules protect the result. On a tile floor, the grout line beneath the dam must be caulked so water cannot travel under it. And the base threshold is never drilled, for any reason, because the base warranty depends on it. The dam attaches to the base with the adhesive and silicone alone.

Shower Dam Compared with Other Entry Options

What the differences mean: the lower the entry, the easier it is to roll or step in, and the more the design relies on the floor slope, the drain and, at the bottom of the range, a dam to keep water where it belongs. A dam is the only one of these options that a wheel can pass over without being lifted. If the person bathing walks in and simply wants less to step over, a 3 inch step-in base or a low-threshold base gives a fixed edge with no strip to maintain. How Deep Is a Shower Pan and Does Depth Matter? compares the threshold heights in more detail, and What is a roll-in shower and who is it designed for? explains the ADA reference figure and why the barrier-free line is the one to look at when an inspector is applying an accessibility code.

Which Bases Include the Dam

The dam comes standard with Ella's roll-in barrier-free bases. Those bases share a 60 inch length and come 30, 32 or 36 inches wide, each with a left or right drain, and the 32 by 60 inch barrier-free base is offered in left and right configurations and is ready to ship. Shower products are sold per item rather than as a bundle, so a complete roll-in shower is put together from the base in your size and drain position, a wall system sized to it, and the dam that ships with the base. Caregiver options such as a weighted anti-bacterial nylon curtain, a stainless curtain rod and a slide bar with hand shower can be added. What is a roll-in shower and who should get one? lists the sizes, seats and accessories, and your Ella dealer or the team at (800) 480-6850 can confirm which drain position matches your floor.

Related Guides

• What sizes do roll-in shower bases come in, and which include a seat?
• Shower Base Sizes and Thresholds Compared: AcrylX Barrier-Free, SMC Linear-Drain, Molded-Seat and Cultured Marble Bases
• Installing Ella Shower Bases, the Flexible Shower Dam, and Shower Walls

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