Can my walk-in tub drain run horizontally to an offset floor drain?

Yes. Every Ella walk-in tub drain is a 2 inch gravity drain whose drain body hangs below the tub floor and ends in a four-port T-type PVC fitting, and from that fitting the pipe runs horizontally beneath the tub, in either direction, to the P-trap your plumber chooses. The floor drain therefore does not have to sit under the tub, and Ella publishes no maximum offset, because the limit is set by your floor and by the size and run of the house drain line rather than by the tub. How far can the floor drain be offset from the tub drain? covers the offset on its own; this page explains the horizontal run, the two accepted trap layouts, and what to keep reachable for service.

A Horizontal Run Beneath the Tub Is the Normal Connection

People asking about a horizontal drain usually mean one of two things: a drain line that runs sideways under the tub instead of dropping straight down, or a drain that exits through the wall. The first is how an Ella tub is always connected. The drain body can be connected from the left, the right or the center, the T-type drains have ports that let the pipe leave in either direction, and the tub can be shifted sideways within the space so its drain lands where the run is shortest. Your plumber picks the most direct path from the tub drain to the existing trap and runs PVC beneath the tub to get there, so pipe direction plus tub position bridges the offset without moving the floor drain.

The second meaning does not apply. Ella tub drains go to the floor rather than the wall, so a floor rough-in is the normal case, and a center floor drain left behind by a freestanding tub is simply a floor rough-in in a less usual spot. Can a Walk-In Tub Use the Center Floor Drain From a Freestanding Tub? walks through that case, including the wall a walk-in tub needs behind its long side that a freestanding tub never did.

The Two Accepted P-Trap Layouts

Most models have two drains, and the dual drain arrives mounted on the tub with four open 2 inch ports. Your plumber has two accepted ways to trap it, and the installation video on this page shows both configurations on a real job, including a customer who used two of the four ports and capped the unused side.

1. A P-trap for each drain. Each of the two tub drains gets its own P-trap and both run into the main drain line. This is the fastest draining layout and the one recommended when there is room under the tub for two traps.
2. One P-trap for both drains. The two drains are combined with a 2 inch tee or wye ahead of a single P-trap, which is the layout to use when only one connection point is available. A Y is preferred over a T because the water changes direction less.

In either layout the drain line runs through the P-trap to a 2 inch vent pipe, slopes downhill to the main, and is trapped and vented to local code. The branch line should be 1 1/2 inches to 2 inches, and standard house plumbing for a bathtub is an inch and a half drain. Two inch main drains are recommended for faster draining, but a T or Y connection into a house drain sized at 1 1/2 inches works. You can connect all four ports for maximum drain speed, or connect the two ports on the convenient side and cap the unused ports with the end caps that ship with the tub. Even one port still works, and there is no drain pump anywhere in the system, so a power failure never leaves you waiting to exit. Can a Walk-In Tub Connect to My Existing Drain and P-Trap? covers what to do when there is no drain line at all where the tub will go.

How Far the Offset Can Go

There is no published figure for how far is too far. The size and run of your house drain line and the clear space under the tub along the path decide what the plumber can connect, and those can only be measured in your bathroom. Before you order, have your installer measure the existing line, and give your Ella dealer or the team at (800) 480-6850 the model name so they can confirm the drain position for that model. With both numbers in hand, the installer knows the distance the pipe has to cover before the tub arrives, and building the new drain line before the tub is set saves a great deal of effort because the final connection is made on site to ports that are already on the tub.

The decision that has to come first is the door side. On every Ella walk-in tub the door is on one side and the drains are on the other: a right-side door tub drains on the left, and a left-side door tub drains on the right, with sides taken as you face the tub. Since the tub drains have to end up on the side nearest your house drain, choose the door side that puts the drain end over or beside your existing plumbing and the horizontal run stays short.

What Stays Reachable for Service

Plan the connections so they can be reached later without opening the floor. The drain line should have a clean out just uphill of the main line for future service, and easily accessible shutoff valves should be placed close to the newly installed tub, with 3/4 inch supply lines strongly recommended for faster filling. The tub itself has a magnetic access panel next to the door, which is where the serial number label sits and where the tub's own equipment is reached, while the drains are at the opposite end from that door. Before the tub comes into the house, the end panels, side panels and aprons must be removed to prevent damage, and once inside the tub must be properly leveled on its adjustable leveling legs, because without proper leveling the door may not function properly and may leak. Those steps, and the two drain configurations, are shown in the video.

If You Are Planning a Shower Base Instead

The flexibility above belongs to the tub, not to Ella shower bases. A shower base or one-piece stall is molded with the drain opening as part of the floor, so its drain cannot be moved on request, and a mismatch is solved by relocating the trap, choosing a base whose molded drain position matches, ordering a custom-size base with the drain placed to suit, or using the reversible SMC base. What if my existing shower drain does not line up with the Ella base? explains how to measure that mismatch from the Specification drawing before you order.

Watch: Ella's Bubbles: Installation Tips For The Ella Big4One with chapters and a full transcript.

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