My House Drain Is 1.5 Inches. Will the 2 Inch Tub Drain Work?

If my house drain is 1.5 inch, will the 2 inch tub drain work? Yes. Every Ella tub drain is 2 inches and gravity driven, and a 2 inch house main is recommended for the fastest emptying, but a standard T or Y fitting into a 1.5 inch house drain works. The first thing to understand is that the house drain size does not change how the tub connects: on dual drain models the two drains join under the tub into a single house connection, so you need one P trap and one reducing fitting, not two drain pipes in the slab. There is no drain pump anywhere in the system.

Likely Causes

• The plumber assumed two drains need two house connections. Both tub drains join under the tub.
• The 2 inch brass outlet looked incompatible with the 1.5 inch riser. A 2 inch to 1.5 inch reducing coupling ahead of the P trap solves it.

What to Check, in Order

1. Confirm the house drain flows well. A dual drain cannot fix a slow house line.
2. Plan one house connection. Connect two of the four T type ports on the convenient side and cap the unused ports with the caps that ship with the tub. All four gives the fastest drain, and even one port still works. The port layout is in plumbing and drain configurations.
3. Step down with a standard fitting. Fit a 2 inch to 1.5 inch reducing coupling on the tub side of the P trap riser, or run a 2 inch PVC 90 off the drain body and reduce ahead of the P trap. Details are in connecting the 2 inch drain to 1.5 inch house plumbing.
4. Use one P trap and prefer a Y. One P trap serving both tub drains is typical, and a Y with fewer elbows drains better than a T because the water changes direction less.
5. Route under the tub if the house drain is on the far side or in the center. There is roughly 3 inches of clearance under the tub for 2 inch PVC, so the plumber can run the drain to either side.
6. Keep the run short, and consider a flexible P trap or no hub coupling at the joint under the tub so the tub can be removed later without cutting pipe, as covered in common plumbing questions.

The video shows a real before and after install with dual P traps and the new main connection, explains that a 2 inch main is recommended but a T or Y into a 1.5 inch drain works, and shows a customer's install using two of the four ports with the unused side capped. Drain speed is explained in dual drain technology and drain speed. Watch: Ella's Bubbles: Dual Drain Technology and House Drain Connection with chapters and a full transcript.

When to Open a Ticket

If your plumber wants to confirm the layout before cutting the slab, open a ticket at ellasbubbles.com/support with your model, the door and drain configuration on your order, a photo or sketch of where the existing house drain sits, and its size. Your Ella dealer or the team at (800) 480-6850 can send the drawing for your model so the rough in lands under the drain end.

Related Guides

• Will a 3-Inch Sewer Line Make My Walk-In Tub Drain Slower Than a 4-Inch Line?
• Connecting the Dual Drains in a Tight Space and What the Drain Package Includes
• Draining to a Washing Machine Box or a Drain Higher Than the Tub: Why Gravity Drains Need a Pump
• Does the Fast Dual Drain Overwhelm Standard Household Drain Piping?

Common Questions