Linear Drain Installation for Curbless Showers in Boise
The modern alternative to center drains. Linear drains enable single-direction floor slopes, seamless curbless thresholds, and large-format tile installations — the foundation of every high-end walk-in shower we build across the Treasure Valley.
A linear drain is a long, narrow drainage channel installed flush with the shower floor that collects water along an entire edge rather than at a single center point. Where a traditional round center drain requires the floor to slope inward from all four directions, a linear drain allows the entire shower floor to pitch in one direction only — creating a clean, consistent plane that is easier to waterproof, simpler to tile, and essential for curbless (zero-threshold) shower designs.
Linear drains have become the standard specification for high-end bathroom remodels across Boise, and for good reason. They eliminate the compound slopes that make large-format tile installation difficult, they enable the seamless floor transitions required for ADA-compliant and aging-in-place showers, and they deliver a minimalist aesthetic that center drains cannot match. Every curbless shower we build in the Treasure Valley starts with a linear drain because no other drain type can achieve a truly flush threshold between the shower floor and the adjacent bathroom floor.
Understanding the anatomy of a linear drain helps homeowners appreciate why these systems cost more than a standard center drain — and why the investment is worth it for curbless shower designs. A linear drain consists of four primary components, each engineered to work together as a watertight assembly.
Channel Body (Trough)
The channel body is the structural backbone of the system — a stainless steel or ABS trough that sits below the finished tile surface and collects water as it flows across the shower floor. Channel bodies are typically 2 to 4 inches wide and available in lengths from 24 to 60 inches. The body includes a built-in slope toward the outlet connection to ensure water moves to the drain pipe even at low flow rates. Premium channels from Schluter and Infinity Drain use 304 stainless steel for corrosion resistance in Boise's mineral-rich water supply.
Grate Cover
The grate sits on top of the channel body and is the only visible component once the shower is complete. Grates come in two fundamental styles: decorative metal grates with patterns (lines, squares, wedge wire) in brushed nickel, polished chrome, matte black, or oil-rubbed bronze finishes, and tile-in covers that hold a cut piece of the same tile used on the shower floor, creating a nearly invisible drain line. The grate is removable for cleaning and maintenance — a critical feature given Boise's hard water mineral buildup.
Bonding Flange
The bonding flange extends horizontally from the top edges of the channel body, providing the surface where the waterproofing membrane bonds to the drain assembly. This is the most critical detail in the entire installation — if the membrane-to-flange connection fails, water bypasses the drain and enters the subfloor. Schluter's Kerdi-Line uses a wide bonding flange specifically designed to integrate with their Kerdi sheet membrane, creating a factory-engineered waterproof connection. Other manufacturers provide flanges compatible with liquid-applied membranes like Laticrete Hydro Ban or RedGard.
P-Trap & Outlet Connection
The bottom of the channel body connects to a standard 2-inch P-trap via a vertical or horizontal outlet, depending on the subfloor configuration. The P-trap maintains a water seal that prevents sewer gases from entering the bathroom — the same function it serves on a center drain, just relocated to accommodate the linear channel's position. In Boise homes with crawl space access, the plumber can route the drain line from below. In slab-on-grade construction, the concrete must be cut to position the P-trap directly below the channel outlet.
Where you position a linear drain fundamentally affects the shower's drainage behavior, floor slope direction, tile layout, and visual design. There is no single “correct” placement — the best position depends on the shower footprint, the desired aesthetic, and whether the shower will be curbless.
Against the Back Wall
The most popular placement for curbless showers. The drain sits along the back wall, and the entire floor slopes from the shower entrance toward the wall at 1/4 inch per foot. Water flows away from the bathroom, keeping the threshold dry. This position hides the drain from direct view when standing outside the shower. It is the default specification for most of our Boise tub-to-shower conversions because it maximizes the usable flat area near the entry and works naturally with the room's floor level transition.
At the Threshold (Entry)
Positioning the drain at the shower entrance creates a water barrier that intercepts runoff before it reaches the bathroom floor. The floor slopes from the back wall toward the entry. This placement is ideal for curbless designs in tight bathrooms where the shower is directly adjacent to other fixtures, because it provides an extra layer of water containment. The trade-off is that the drain grate is visible and walked over every time someone enters the shower.
Center of the Shower
A center-placed linear drain runs across the middle of the shower floor, with the floor sloping toward it from both sides. This creates two slope planes rather than one, adding tile complexity, but it reduces the maximum slope height since each half has a shorter run. Center placement is occasionally used in very large showers (over 5 feet deep) where the total fall from wall to opposite wall would exceed comfortable standing tolerances at 1/4 inch per foot across the full distance.
Not all linear drains are created equal. The brands we specify for Boise installations are chosen for proven waterproofing integration, build quality, local supply chain availability, and long-term performance in Idaho's hard water conditions. Here is how the four leading brands compare.
| Brand | Price Range | Material | Best For | Waterproofing |
|---|---|---|---|---|
| Schluter Kerdi-Line | $300–$600 | 304 Stainless | Kerdi membrane systems | Kerdi band integration |
| Infinity Drain | $500–$1,200 | 304 Stainless | Custom lengths & tile-in | Universal flange |
| QuickDrain | $350–$700 | 304 Stainless | Shallow subfloors | ProLine flange system |
| Laticrete Hydro Ban | $250–$500 | ABS/Stainless | Liquid membrane systems | Hydro Ban bonding |
Schluter Kerdi-Line
Our most-installed linear drain because it integrates directly with the Schluter Kerdi waterproofing system we use on the majority of our shower builds. The Kerdi-Line's bonding flange accepts Kerdi band membrane strips that create a factory-designed watertight seal between the drain and the shower pan. This eliminates the guesswork of adapting a third-party drain to a membrane system. Available in 20 to 48-inch lengths with both tile-in and brushed stainless grate options. Readily stocked at Boise tile suppliers including Idaho Custom Tile and Floor Craft.
Infinity Drain
The premium choice for custom and luxury showers. Infinity Drain offers the widest selection of grate patterns, finishes, and custom lengths in the industry — including made-to-order sizes up to 96 inches for oversized showers. Their tile-in (site-sizable) grate covers are the best in the market for achieving a truly invisible drain line. The universal bonding flange works with both sheet and liquid-applied membranes. Higher price point, but the quality and design options are unmatched for high-end master bathroom conversions in Boise's East End, North End, and Eagle custom homes.
QuickDrain
QuickDrain's primary advantage is its low-profile channel body, which requires less subfloor depth than competing products. This makes it the go-to specification for remodels where joist depth or slab thickness limits the available space for the drain assembly. The ProLine series includes a pre-sloped channel body, reducing the precision required during rough-in framing. A practical mid-range option that performs well in standard residential installations across Boise.
Laticrete Hydro Ban Linear Drain
Designed specifically for use with Laticrete's Hydro Ban liquid-applied waterproofing membrane. The bonding collar accepts liquid membrane application directly, creating a seamless waterproof transition from shower floor to drain body. The most affordable option in our lineup and a solid performer for standard residential showers where the Laticrete waterproofing system is already specified. ABS channel body with stainless steel grate options.
The grate cover is the only visible part of a linear drain, and the choice between a tile-in cover and a decorative metal grate affects both the aesthetic and the maintenance profile of the shower. Both options perform identically from a drainage standpoint — the difference is entirely visual and practical.
Tile-In Grate Covers
Nearly invisible — the grate holds a cut piece of your shower floor tile, leaving only a narrow perimeter slot visible
Creates the cleanest aesthetic for minimalist and spa-inspired bathroom designs
Best paired with large-format porcelain or natural stone tiles where visual continuity is the priority
Slightly more difficult to clean because debris collects in the narrow perimeter gap
Requires precise tile cutting during installation to fit the grate frame exactly
Available from Schluter (Kerdi-Line frameless), Infinity Drain (site-sizable), and QuickDrain (TileIn series)
Decorative Metal Grates
Visible design element — available in wedge wire, square slot, linear slot, brick, and custom patterns
Finish options include brushed nickel, polished chrome, matte black, satin brass, and oil-rubbed bronze
Easier to clean because the full grate lifts out, exposing the entire channel for wiping and flushing
Can coordinate with other bathroom hardware (faucets, towel bars, showerhead) for a cohesive metal palette
Adds a subtle visual accent line that defines the shower zone in open-concept bathroom layouts
Slightly lower cost than tile-in options because no precision tile cutting is required for the grate itself
A linear drain must be sized to handle the total water volume delivered by all showerheads in the enclosure. Undersizing the drain creates standing water, pooling at the threshold, and potential water damage outside the shower area. The calculation is straightforward but often overlooked by less experienced installers.
| Shower Configuration | Total GPM | Min. Drain Length | Recommended Drain |
|---|---|---|---|
| Single showerhead (standard) | 2.5 GPM | 24 inches | 24–30 inch |
| Handheld + fixed head | 4.0–5.0 GPM | 30 inches | 30–36 inch |
| Rain head + body sprays | 6.0–8.0 GPM | 36 inches | 36–48 inch |
| Dual rain heads (luxury) | 10.0+ GPM | 48 inches | 48–60 inch |
Flow rates based on EPA WaterSense standards (2.5 GPM max for fixed heads, 2.0 GPM for handheld). Actual GPM varies by fixture; always verify manufacturer specifications. We size drains with a minimum 25% safety margin above calculated total GPM.
The connection between the waterproofing membrane and the linear drain bonding flange is the single most important detail in the entire shower installation. If this joint fails, water bypasses the drain entirely and saturates the subfloor, framing, and potentially the ceiling below. Every leak we have repaired in a Boise bathroom that involved a linear drain traced back to a membrane-to-flange failure — not a failed drain body or a cracked tile.
Schluter Kerdi Membrane to Kerdi-Line
The Kerdi sheet membrane overlaps the Kerdi-Line bonding flange by a minimum of 2 inches on all sides. Schluter Kerdi-Band (a flexible waterproof strip) is applied over the overlap using unmodified thin-set mortar, creating a continuous waterproof envelope from the shower walls down across the floor and into the drain channel. This is a system-matched connection — every component is engineered by the same manufacturer to bond together, eliminating compatibility questions.
Liquid-Applied Membranes (Hydro Ban, RedGard)
For drains with universal bonding flanges (Infinity Drain, QuickDrain), the liquid membrane is applied directly over the flange using a brush or roller, building up to the manufacturer-specified mil thickness (typically 30-60 mils wet). A fabric reinforcement strip is embedded in the first coat over the flange-to-substrate transition to bridge any micro-gaps. A second coat is applied over the fabric after the first coat cures. This method requires precise application and full cure time verification before tiling.
Flood Testing Before Tile
Before any tile is installed, we flood-test the completed waterproof assembly by plugging the drain outlet, filling the shower pan with 1 to 2 inches of water, and monitoring for 24 hours. Any drop in water level indicates a membrane breach that must be identified and repaired before proceeding. This step is required by the Tile Council of North America (TCNA) and is our non-negotiable standard on every shower build in Boise.
The floor slope is the primary reason contractors and homeowners choose linear drains over center drains. A center drain requires a four-way compound slope where the floor pitches from all four walls toward the center point, creating a subtle pyramid shape. A linear drain requires only a single-direction slope — the floor tilts uniformly from one wall to the opposite wall where the drain is positioned.
The standard pitch for both configurations is 1/4 inch per foot, as specified by the International Plumbing Code and required for Boise permits. In a typical 5-foot-deep shower with a back-wall linear drain, the floor rises 1.25 inches from the drain to the shower entrance. This gentle slope is virtually undetectable underfoot but sufficient to move water efficiently toward the channel.
For tile installation, the single-direction slope is transformative. Large-format tiles (12×24, 24×24, and larger) can be laid flat across the shower floor with consistent grout lines because the substrate is a single plane. With a four-way slope for a center drain, these same tiles must be cut into triangular sections (called “pie cuts”) to follow the compound surface — an arrangement that looks dated, complicates waterproofing at the cut lines, and defeats the purpose of using large-format tile. If you are planning a shower floor with tiles larger than 4×4 inches, a linear drain with single-direction slope is the correct specification.
Converting from a standard tub drain or center shower drain to a linear drain involves plumbing modifications that must comply with City of Boise and Ada County codes. These are the specific considerations our plumbing team evaluates on every linear drain project in the Treasure Valley.
Drain Line Relocation
Most existing tub and shower drains are centered in the fixture footprint. Moving to a wall-mounted linear drain typically requires relocating the 2-inch drain pipe 18 to 30 inches from its current position. In homes with crawl space access — common across the Boise Bench, North End, and Southeast Boise — this relocation is done from below without disturbing the finished ceiling of the floor below. In slab-on-grade homes found in parts of Meridian, Nampa, and newer West Boise subdivisions, the concrete must be saw-cut, the pipe repositioned, and the slab patched.
Vent Requirements
Idaho plumbing code (based on the IPC) requires every shower drain to be vented to prevent siphoning of the P-trap water seal. When relocating a drain for a linear channel, the existing vent connection may need to be extended or re-routed to maintain proper venting within the code-required distance from the trap. Our licensed plumbers verify vent compliance during the rough-in phase, before any waterproofing or tile work begins.
Pipe Sizing & P-Trap Access
Residential showers in Idaho require a minimum 2-inch drain pipe. All linear drain brands we install connect to standard 2-inch ABS or PVC waste pipe via a solvent-welded or compression fitting at the channel body outlet. The P-trap must remain accessible for maintenance — in homes with crawl spaces, this is inherently satisfied. In slab-on-grade installations, we use a cleanout fitting at the trap to provide maintenance access without demolishing the shower floor.
Linear drains cost more than standard center drains, but the premium buys you curbless capability, single-direction sloping, large-format tile compatibility, and a modern aesthetic that center drains cannot deliver. Here is the cost breakdown for linear drain installations in the Boise metro area.
| Component | Cost Range | Notes |
|---|---|---|
| Linear drain unit | $300–$1,200 | Varies by brand, length, and grate finish |
| Plumbing rough-in / relocation | $300–$800 | Crawl space access vs. slab-on-grade |
| Subfloor framing & slope prep | $200–$500 | Single-direction slope build-up |
| Waterproofing integration | $150–$350 | Membrane-to-flange connection + flood test |
| Additional tile labor | $200–$400 | Precision cuts around drain channel |
Total premium over a standard center drain installation: $700 to $2,000. For context, the total cost of a typical tub-to-shower conversion in Boise ranges from $8,000 to $15,000, making the linear drain upgrade a 5% to 15% addition that fundamentally changes the shower's design capability and long-term usability.
Costs reflect 2026 Boise-area pricing including materials, labor, and permit fees. Actual costs vary by home construction type, drain brand selection, and scope of plumbing modifications. Slab-on-grade homes typically incur higher plumbing relocation costs than homes with crawl space access.
Linear drains require slightly more maintenance attention than center drains because the elongated channel body and narrow grate slots can accumulate debris and mineral deposits faster. In Boise's moderately hard water environment (7–11 grains per gallon municipal, up to 15+ grains on well water), calcium and lime scale buildup is the primary maintenance concern.
Every 2 weeks: Lift the grate cover and remove the hair trap basket. Clear any accumulated hair, soap residue, and debris. Rinse the basket under running water before replacing. This takes less than two minutes with tool-free grate removal designs from Schluter, Infinity Drain, and QuickDrain.
Monthly: With the grate removed, wipe the interior of the channel body with a cloth dampened in white vinegar solution (1:1 vinegar to water). This dissolves early-stage mineral deposits before they harden into scale that requires more aggressive removal.
Quarterly: Apply a calcium-lime-rust (CLR) remover or citric acid solution to the grate, channel body, and the narrow gap between the grate frame and surrounding tile. For tile-in grate covers, use a thin brush or old toothbrush to clean the perimeter slot where mineral deposits concentrate.
Annually: Flush the channel body and P-trap with hot water and enzymatic drain cleaner to clear any biofilm or organic buildup in the trap. Inspect the grate for any warping, finish deterioration, or gasket wear. Replace hair trap baskets if the mesh is deformed or corroded.
Can a linear drain be installed in any shower in Boise?
In most cases, yes, but there are structural and plumbing prerequisites that must be evaluated first. Linear drains require the shower floor to slope in a single direction toward the drain channel, which means the subfloor framing must allow for the necessary pitch — typically 1/4 inch per foot across the full width of the shower. In slab-on-grade homes common in parts of West Boise and Meridian, cutting a trench into the concrete for the drain channel body and repositioning the P-trap adds significant labor. In homes with crawl space access — typical across the Boise Bench and North End — relocating the drain line from center to wall position is more straightforward because the plumber can work from below. Our site evaluation checks joist direction, subfloor depth, existing drain location, and available fall to determine if a linear drain is feasible without major structural modifications.
How do linear drains compare to center drains for curbless showers?
Linear drains are the preferred choice for curbless (zero-threshold) shower designs because they collect water along an entire edge rather than a single point. With a center drain, the floor must slope from all four directions toward the middle, creating a compound pitch that is difficult to tile with large-format tiles and nearly impossible to make truly flush with the bathroom floor at the threshold. A linear drain positioned at the shower entrance or against the back wall allows the entire floor to slope in one direction at a consistent 1/4 inch per foot. This single-direction slope is easier to waterproof, simpler to tile, and produces a cleaner visual line. For ADA-compliant and aging-in-place showers — which are increasingly requested across Boise — linear drains are effectively the standard because they enable the seamless floor transition that wheelchair access and walker clearance require.
What maintenance does a linear drain need with Boise's hard water?
Boise's municipal water is moderately hard at 7 to 11 grains per gallon, and well water in surrounding areas like Star, Eagle, and Kuna can exceed 15 grains. This mineral content causes calcium and lime scale to accumulate on the drain grate, inside the channel body, and around the hair trap basket faster than in soft-water regions. We recommend lifting the grate and cleaning the hair trap basket every two weeks, wiping the channel interior with a white vinegar solution monthly, and descaling the grate with a calcium-lime-rust remover quarterly. Tile-in grate covers require extra attention because mineral deposits build up in the narrow gap between the grate frame and the surrounding tile. Most linear drains from Schluter, Infinity Drain, and QuickDrain are designed for tool-free grate removal, making routine cleaning a two-minute task. Neglecting maintenance in a hard-water environment eventually restricts flow capacity and can cause water to pool at the shower threshold rather than draining efficiently.
How much does a linear drain installation cost in Boise?
The total cost for a linear drain installation in the Boise metro area ranges from $800 to $2,700 depending on the drain brand, length, finish, and the complexity of connecting to existing plumbing. The drain unit itself runs $300 to $1,200 — a basic 24-inch Schluter Kerdi-Line is at the lower end, while a 48-inch Infinity Drain with a custom tile-in grate is at the upper end. Installation labor adds $500 to $1,500 beyond what a standard center drain installation would cost, because the installer must frame and slope the shower pan in a single direction, cut and position the channel body precisely, connect the P-trap and drain line (often requiring relocation of the existing 2-inch drain pipe), and integrate the waterproofing membrane to the drain flange. The premium over a standard center drain is typically $700 to $2,000 total, which is a modest investment relative to the total cost of a tub-to-shower conversion project in the $8,000 to $15,000 range.
Does Boise building code allow linear drains for shower installations?
Yes. The City of Boise and Ada County follow the International Plumbing Code (IPC), which permits linear drains provided they meet specific requirements. The drain must connect to a minimum 2-inch waste pipe (the standard for residential showers in Idaho), include an accessible P-trap, and the drain body must be listed to an approved standard such as ASME A112.6.3. The flow rate of the drain must meet or exceed the combined flow of all showerheads served — for a standard single-head shower at 2.5 GPM, any linear drain 24 inches or longer will exceed this requirement with significant margin. For multi-head or rain shower configurations common in master bathroom conversions, we size the drain to handle the combined GPM and verify the vent configuration meets IPC requirements. All of our linear drain installations are completed under permit and pass City of Boise or Ada County plumbing inspection.
Linear drains are one component of a complete tub-to-shower conversion. Explore related services and guides to plan your full bathroom remodel project.
The following government agencies, industry organizations, and official resources provide additional information relevant to your remodeling project.
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