Can a Walk-In Tub Connect to My Existing Drain and P-Trap?

Yes. An Ella walk-in tub connects to a standard P-trap and to the house drain you already have, and when the floor drain is not directly under the tub the connection is made by running PVC beneath the tub to the trap. Every Ella tub drain is 2 inches and gravity driven, most models have two drains that each end in a four-port T-type PVC fitting, and your plumber ties them into a 1 1/2 inch or 2 inch house drain with a standard T or Y fitting, as laid out in Plumbing and drain configurations: connecting your walk-in tub to the house drain. This page covers the two accepted P-trap layouts, what to do when there is no drain line at all where the tub will go, and what a center floor drain left behind by a freestanding tub means for the plan.

The Two Accepted P-Trap Layouts

The dual drain arrives mounted on the tub with four open 2 inch ports, and your plumber has two accepted ways to trap it.

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. One P-trap serving both tub drains is typical, and 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, with a clean out just uphill of the main line for future service. The branch line should be 1 1/2 inches to 2 inches. 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.

When There Is No Drain Line Where the Tub Will Go

A tub does not need a drain already in the right spot. Installers often move the drain and supply lines, 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 one thing the new line cannot ignore is the door side. On every Ella walk-in tub the door is on one side and the drains are on the other, so 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, and two-seat models drain in the center. Settle the door side first, because it fixes the end of the tub the new drain has to reach.

Ella does not publish a single fixed rough-in point for the drain, because the exact outlet position can vary slightly from tub to tub. The sequence that works for a new floor or slab is described in What Plumbing and Electrical Rough-In Does a Walk-In Tub Need in New Construction? and comes down to this:

1. Confirm the door side on your order, which fixes the drain end.
2. Ask your Ella dealer or the team at (800) 480-6850 for the spec sheet and the approximate drain distances for your model.
3. Rough in the trap with a slight allowance in both directions rather than a rigid stub.
4. Set the tub level in its final spot, measure the actual outlet, and make the final trap connection.
5. Have your plumber confirm the house drain is sized and vented correctly.

This is the opposite of an Ella shower base, where the drain position is molded into the base and fixed for each model, as explained in Can I Choose a Left, Right, or Center Drain on an Ella Shower?. A shower rough-in is set to a drawing, while a tub rough-in is finished after the tub is on site, which is exactly what gives the tub its flexibility with an existing trap.

A Center Floor Drain Left by a Freestanding Tub

If the old tub was a freestanding model with the drain and the water supply in the center of the floor, that rough-in can usually be used. Ella tubs have no fixed drain direction, so the plumber routes the connection whichever way suits the room. The drains sit at the end opposite the door, and when the house drain lands elsewhere, including the center of the floor, the piping is run underneath the tub, where there is roughly 3 inches of clearance above the floor for 2 inch PVC. Keep that run short, and consider a flexible P-trap or a no-hub coupling at the joint under the tub so the tub can be removed later without cutting pipe.

Two more things change when a walk-in tub replaces a freestanding one. The back of a walk-in tub needs a wall, or a contractor-built knee wall, where the freestanding tub may have stood in open floor, and the tub needs a dedicated GFCI protected outlet nearby for its equipment. On the supply side, the Ella faucet connects with 3/4 inch female pipe thread and the two included braided lines are 5 feet long, so the shut-off valves need to sit within that reach of the faucet position on the deck.

A 1.5 Inch House Drain and an Offset Floor Drain

A 2 inch house main is recommended for the fastest emptying, but a standard T or Y into a 1.5 inch house drain works. The step down is made with a 2 inch to 1.5 inch reducing coupling on the tub side of the P-trap riser, or by running a 2 inch PVC 90 off the drain body and reducing ahead of the trap, as detailed in My House Drain Is 1.5 Inches. Will the 2 Inch Tub Drain Work?. A dual drain cannot fix a slow house line, so confirm the existing drain flows well before anything else.

When the floor drain is to one side of where the tub drain lands, the drain body lets the plumber connect from the left, the right or the center, the T-type ports let the pipe leave in either direction, and the tub can also be shifted sideways within the space so its drain is offset from the house drain. Ella does not publish a maximum offset, because the practical limit is set by your floor and by the size and run of the house drain line rather than by the tub, and How far can the floor drain be offset from the tub drain? explains how the installer measures that before you order.

What to Send Before You Order

Give the team your model name and door side, the location of the existing drain measured from the walls, the distance from that drain to where the tub drain will land, and the size of the house drain line, or send photos of the open floor. With those in hand the drawings for your model can be checked against the space before anything is ordered, and your plumber knows the distance the pipe has to cover before the tub arrives. Ella does not send technicians, so the trap and the final drain connection are made by your local licensed plumber, with the team available by phone or video for questions about the tub side of the connection.

Related Guides

• Connecting the Dual Drains in a Tight Space and What the Drain Package Includes
• How does the Ella dual drain speed up draining a walk-in tub?
• Is the Flexible Drain Hose Still Available? The PVC Elbow That Replaced It

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