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How Close to the Wall Can the Drain Be on a Custom Shower Base, and Can It Be Centered?

Updated September 2026

▶Glossary7
  1. Why 9 Inches Is the Minimum
  2. How to Specify the Drain Position
  3. What Happens Before Production
  4. Related Reading
  5. Related Guides
  6. Common Questions
  7. Still Need Help?

On a custom-size Ella shower base, the drain must sit at least 9 inches from the back wall and at least 9 inches from the nearest side wall, measured from the outside edge of the base. This limit comes from the molds used to form the base, so it applies to every custom size and threshold option. Within that limit the drain can be centered or offset, and the team confirms the exact drain measurements with you in writing before the base goes into production, so nothing is built until you have approved the numbers.

Why 9 Inches Is the Minimum

Custom bases are made from a molded acrylic sheet backed by high-density foam. That construction is what makes them light, and it is the only way a custom size can be produced. The drain position is set by the molds available, and those molds cannot place the drain closer than 9 inches to an edge that meets a wall. A drain has occasionally been placed a little closer for a specific project after the molds were reviewed, but that is not a standard option and cannot be promised. If your existing drain line is closer than 9 inches to a wall, ask the team to review your dimensions before you order, and plan with your plumber for the possibility that the drain connection under the floor will need to move.

The base also cannot be trimmed on site. It arrives at the exact size you ordered, so measure carefully and have your contractor confirm the numbers before you approve them. Custom size ranges, threshold options and construction are covered in the main custom base article.

How to Specify the Drain Position

The order asks for two drain measurements, called C and D, which together locate the center of the drain opening. The drawing the team sends shows exactly where each one is measured from.

  1. Measure the overall width and depth of the space wall to wall, and tell the team whether the base sits in a three-wall alcove or another layout.
  2. Choose the threshold. Custom bases are made with a 2-inch or a 4-inch threshold; a zero threshold is not available on a custom size.
  3. Measurement C sets the drain position across the width of the base. For a centered drain, C is half the width. On a 36-inch-wide base, for example, C is 18 inches.
  4. Measurement D sets the drain position from front to back. It must leave at least 9 inches to the back wall.
  5. For an offset drain, state clearly which side the drain is nearest and keep at least 9 inches to that side wall. The team will double-check which side you mean before production.
  6. Send the measurements in writing, ideally as a simple dimensioned sketch, and wait for the team's written confirmation.

What Happens Before Production

When an order simply says "left-hand drain" or "right-hand drain," the team reaches out by email for the specific C and D numbers so nothing is left to interpretation. If the position you request cannot be made with the available molds, the team tells you the closest position that can be made and asks you to approve it. Once you approve, the base is built to those numbers.

For a comparison of standard bases and thresholds, see shower base sizes and thresholds compared. For how the acrylic base is set on the floor, see how the acrylic shower base is installed.

Common Questions

Can the drain be exactly centered on a custom shower base?
Yes, as long as the centered position keeps the drain at least 9 inches from the back wall. Give the team a C measurement equal to half the base width, and the team confirms the exact C and D figures with you before production.
What if my existing drain is closer than 9 inches to the wall?
Standard custom bases cannot be built with the drain closer than 9 inches to a wall. A closer placement has occasionally been reviewed for a specific project, but it cannot be promised. Ask the team to review your dimensions before ordering, and talk with your plumber about relocating the drain line.
Can I trim a custom shower base to fit my space?
No, a custom Ella shower base cannot be trimmed on site. The base is constructed from a molded acrylic sheet backed by high-density foam, and this construction prevents it from being cut or trimmed. You must order the exact size needed for your space, and your contractor should verify all measurements before you approve them for production.
What do the C and D drain measurements mean?
C locates the center of the drain across the width of the base, and D locates it from front to back. Both must respect the 9-inch minimum from any wall. Send them in writing so the team can confirm them before production.
Is a zero threshold available on a custom base?
No, a zero threshold is not available on a custom-size Ella shower base. Custom bases are manufactured with either a 2-inch or a 4-inch threshold. For a comparison of threshold options available on standard shower bases, you can refer to the shower base sizes and thresholds compared article.
Why does the team email me about the drain position after I order?
The team emails you about the drain position after you order because a general note like "right-hand drain" is not specific enough for production. The team needs the exact C and D measurements, which locate the center of the drain opening, to ensure the drain is placed precisely where your plumbing requires it. Production of your custom shower base will not begin until you have confirmed these specific drain measurements in writing.

Still Need Help?

Open a ticket at ellasbubbles.com/support or call (800) 480-6850 and have your model and serial number ready.

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