How to replace an 18 inch rough-in toilet
There are no modern toilets manufactured with an 18-inch rough-in, forcing homeowners to figure out how to retrofit standard models to their existing bathroom. This process is complicated by older four-bolt setups that use floor studs instead of a standard flange. Without a standard flange, people are left guessing exactly where the plumbing pipe is centered.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1Build a custom false wall to bring the wall closer to 12 inches
- 2Blowing up the bathroom floor to change plumbing
- 3Leaving front bolts redundant or removing them
- 4Using the existing closet collar for the back bolts
- 5Asking online plumbing communities for compatibility advice
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“they were able to replace 2/3 but the one in the Owner bathroom had a 18 inch rough-in measurement.”source ↗
“And after research their are no modern Toliets with an 18inch rough-in.”source ↗
“Does anyone have any experience on how to retrofit to a modern toilet?”source ↗
“My main question is its 12” from wall to back bolts, I assume the pipe is centered between the bolts?”source ↗
“What about because my existing toilet has 4 bolts? I’d assume (but I don’t know) that they are studs coming from the floor, not a flange.”source ↗
Where this came up
People with this problem also raised
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