Hi all,
I’m looking for installer advice on a replacement installation (not a new build).

Model:

• TOTO Hayon BTW – CW252PJT1WS / SW252JPT1/252-8P
• S7 Washlet – TCF4732AT
• S-trap adaptor – THX918 (spec rough-in 140–220 mm)

Site context:

• Existing toilet replacement
• Floor waste position is fixed
• Isolation valve is on the opposite side to the pan’s service opening
• Washlet requires two flexible water connections (cistern + washlet) plus power
• Water will be split at the angle valve / tee after isolation (nothing concealed behind the pan)

Important constraint:
This Hayon pan provides a service opening on one side only.
The opposite side does not allow practical routing of flexible hoses or the washlet connection.
Because the valve is on the other side, hoses must route behind the pan.

Reference images attached:

1. TOTO installation drawing showing “0 mm recommended dimension” (reference datum)
2. Product image of Hayon BTW with S7 Washlet

Clarification:
Back-to-wall describes concealed plumbing; it does not require the ceramic pan to be in physical contact with the finished wall tiles.

Question:
Although the drawing shows a 0 mm reference to the wall, in a real replacement install there are flexible hoses, bend-radius requirements, and a power cord.
To avoid hose compression or cable stress, is it acceptable practice to leave a small rear gap (~15–20 mm) on a BTW smart toilet, provided that:

• the S-trap adaptor is within spec range
• nothing is pinched or stressed
• isolation is at the valve
• all joints remain accessible

I’d appreciate confirmation from installers who’ve done similar TOTO BTW + washlet replacement installs.

Thanks in advance.

Toto