Toto Home Additions & ADU Nationwide

Toto Home Additions & ADU: The Sunnyvale Owner’s Guide

Toto bathroom fixtures are specified in roughly 60 percent of the home additions and ADUs we build in Sunnyvale, typically running $900-$2,800 per bathroom depending on the series and rough-in configuration. A full Toto-equipped secondary bath in an ADU runs $4,500-$8,500 installed, including the Drake II or Ultramax II toilet, Guinevere or Soiree vanity faucet, and compatible valve rough-ins. We stock common Toto valve bodies, flappers, and fill valves on our Sunnyvale trucks, and we source bowls, tanks, and integrated washlet rough-ins within 24 hours from our San Jose supply house.

Call (650) 405-3637

Most Sunnyvale owners discover a Toto part issue during the final inspection walkthrough or the first month of occupancy. The washlet seat loses pressure, the dual-flush tower sticks, or the EcoPower faucet valve chirps. In Lakewood Village, we’ve seen hard water scale from the Hetch Hetchy supply clog the 1.28-gpf flush tower in under two years. The symptom looks like a weak flush; the cause is usually mineral buildup on the tower seal, not a bowl defect.

Which Toto Models This Applies To

Toto’s residential line breaks into three tiers, and the parts are not cross-compatible. The Drake II (CST454CEFG) and Ultramax II (MS604114CEFG) use the THU331 flush valve with a 3-inch flapper, while the older Drake original uses a 2-inch. The Carlyle II and Vespin II one-piece toilets share the same flush valve but use a different tank-to-bowl gasket. If you’re matching a part, check the sticker inside the tank lid: the model prefix tells us the series, and the suffix tells us the finish and height.

The washlet line (C100, C200, S300e, S500e, S550e) uses proprietary water lines and mounting plates. The C100 and C200 share a 7/8-inch T-connector; the S-series uses a slimmer electronic valve with a different thread pitch. We keep C100/C200 hardware in stock; S-series valves we order overnight. For faucets, the TLG series (Guinevere, Soiree, Wyeth) uses standard 1/2-inch NPT connections, but the EcoPower line requires a 0.5-gpm flow restrictor that most box stores don’t carry. We source OEM Toto parts through our Ferguson and HD Supply accounts; aftermarket equivalents exist for flappers and fill valves, but we specify OEM on anything electronic or pressure-dependent.

Signs Your Toto Home Additions & ADU Is Failing

• Weak or incomplete flush. The 3-inch flush tower on Drake II and Ultramax II units can develop calcium bridging from Sunnyvale’s moderately hard municipal water. The flapper lifts but the seal doesn’t break cleanly, leaving waste in the bowl. We see this most in ADUs where the toilet sits unused for days between guest visits.
• Constant or intermittent running. The Korky 528T fill valve, standard in most Toto tanks, has a float cup that binds if sediment enters the supply line. The valve thinks the tank is empty and refills every 10-15 minutes. In new construction, this usually traces to debris left in the rough-in during drywall.
• Washlet spray pressure drops or pulses. The internal filter on C200 and S550e units clogs with fine sediment. The user feels a stutter in the spray; the cause is a 100-micron screen that Toto recommends cleaning every six months, which almost no one does.
• EcoPower faucet chirps or cycles without hand presence. The micro-turbine in these sensor faucets generates its own power, but the capacitor degrades after 3-5 years. The chirp is the turbine hunting for enough charge to open the solenoid.
• Tank sweat or condensation pooling on the floor. The insulated tank on the Ultramax II can crack at the seam if overtightened during installation. The crack is hairline and vertical; the symptom is moisture that looks like condensation but doesn’t respond to room temperature changes.

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Replacement Cost & What’s Included

These are Sunnyvale market rates, calibrated to our 2024-2025 job data. The labor range moves with access: a toilet in a water closet with a pocket door takes longer than one in an open ADU bath. Under Clause 1 of the Haven Standard, every quote is a flat written price with parts, labor, and any subcontractor scope listed separately. No work proceeds without that signed number. Our 365-Day Done Right Promise covers the installation and the part; if the flush tower we installed sticks in month eight, we replace it at no charge.

DIY or Call Us?

What you can safely check: the water supply angle stop, the tank lid model sticker, and whether the flapper chain has too much slack. These take five minutes and a flashlight. If the fill valve is hissing, shut the stop and see if the noise stops; that tells you whether the issue is valve or supply pressure.

Where DIY goes wrong: the 3-inch flush tower on modern Totos requires a specific torque on the mounting nut. Too tight and the tower body cracks; too loose and it leaks slowly into the bowl, driving up your water bill for months before you notice. The washlet electrical rough-in involves a GFCI-protected outlet within 3 feet of the bowl; if you’re replacing a standard toilet with a washlet-ready unit, the electrical is not a homeowner job in California. We’ve been called to three Sunnyvale ADUs in the past two years where the owner ran an extension cord under the bathroom door. That’s a code violation and a genuine shock hazard in a wet location.

Call (650) 405-3637 and we’ll scope it in person. Estimates are free, and we bring the common parts on the first visit.

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