Not every shower renovation starts from a rough drain stub. Sometimes there's already a drain — with a clamping ring, a traditional bonded membrane connection, or another non-KERDI flange — and you need to convert it to work with the KERDI waterproofing system. That's exactly what the KERDI-DRAIN-A Adaptor Flange Kit is for.

The KERDI-DRAIN-A adaptor kit equips existing clamping ring-type shower drains with a KERDI-compatible bonding flange. Instead of removing the entire drain body from the plumbing rough-in (which can be a major undertaking in a slab or finished floor), you adapt what's there to accept KERDI membrane waterproofing. The 7-1/2" ABS flange is for larger drain openings in the floor assembly.

When you use this instead of a full KERDI-DRAIN

• Remodeling an existing shower with an existing drain body that's still functional
• Slab construction where replacing the drain body would mean concrete demo
• Converting a traditional membrane shower to KERDI waterproofing while keeping existing plumbing
• Any situation where the drain stub can't practically be changed, but the waterproofing system needs to be

How it works

The adaptor kit installs over or into the existing drain opening. Its bonding flange — covered in fleece, just like a full KERDI-DRAIN body — provides the surface for the KERDI waterproofing membrane to bond into mortar. Once installed, the KERDI membrane laps onto the flange in exactly the same way as a standard KERDI-DRAIN installation.

What it pairs with

• KERDI membrane (for full floor/wall waterproofing system)
• KERDI-DRAIN grate kits — Classic 4", Contour, Trendline, or Tile styles — select separately based on grate opening size compatibility
• KERDI-DRAIN-A with 4" SS grate (also available as a bundled kit)

Pro Tips

• Verify the existing drain diameter and outlet type before ordering — the 7-1/2" refers to the outer diameter of the adaptor flange, not the outlet pipe size. Match the adaptor to your existing drain opening
• If the existing drain body is loose, damaged, or at the wrong height, a full KERDI-DRAIN body replacement is the better long-term answer — don't adapt a compromised drain
• Use KERDI-FIX sealant around the adaptor flange perimeter before bonding the KERDI membrane — this seals the joint between adaptor and existing floor surface where mortar alone may not fully penetrate
• Document the drain body type and depth for future reference — this information is helpful if the installation needs service or a grate replacement years down the road