Short definition
A tub-shower combo is a tub fitted with both a tub spout (for filling) and a shower head (for showering), all served by a single mixing valve. A diverter — a tub-spout pull-up or a three-handle center diverter — routes water to either the spout or the head. Modern combos must use an ASSE 1016 anti-scald valve (max 120°F discharge) per UPC 408.3.
What it is
The plumbing components in a tub-shower combo:
- Mixing valve. Single-handle (modern, ASSE 1016) or two-handle hot/cold; sits behind the trim plate at faucet height.
- Tub spout. Mounted lower on the wall (4 to 6 inches above tub rim, manufacturer recommendation).
- Shower arm and head. Mounted higher (shower head typically 78 to 84 inches above floor).
- Diverter. Either integrated into the tub spout (pull-up rod) or a separate handle on a three-handle valve.
Vertical run between valve and shower arm goes up the wall; the tub-spout supply tees off the same vertical at the bottom. Diverter operation closes one branch and opens the other.
Code, per UPC 408.3 and WAC 51-56:
- All new tub-shower-combination control valves must be ASSE 1016 (anti-scald / pressure-balance or thermostatic mixing).
- Maximum discharge temperature: 120°F.
Why it matters to a homeowner
Tub-shower combos are the standard residential bath layout in WA tract and production housing built since the 1950s.
The most common homeowner-noticed problems:
- Diverter failure (tub-spout pull-up doesn’t stay up, or both spout and head run together). Replace the tub spout. $20 part; 15-minute DIY.
- Shower scalding when toilet flushes. Pressure-balance valve failure — see anti-scald valve. The fix is a new ASSE 1016 valve.
- Three-handle valve dripping at one or more handles. Compression-style faucet repair on each handle (washers).
For homes built before 1990, the original valve is often not ASSE 1016. Any code-permitted bathroom remodel triggers the upgrade — a single-handle ASSE 1016 valve replaces the older two- or three-handle setup. Costs:
- Tub-shower valve plus trim (rough-in part): $120 to $400.
- Pro install in new wall: $400 to $800.
- Pro retrofit through existing tile and wall: $800 to $2,000.
Common variants
- Single-handle tub-shower (modern, ASSE 1016). Code-compliant default for new install.
- Three-handle tub-shower (older). Hot, cold, and diverter as separate handles. Pre-1990 design; not compliant in new install.
- Two-handle tub-shower. Hot and cold; tub-spout diverter. Older; typically not compliant for new work.