Toto Home Additions & ADU Nationwide

Toto Home Additions & ADU: The Mountain View Owner’s Guide

We stock and install Toto-compatible fixtures and rough-in components for home additions and ADU projects in Mountain View, with typical installed pricing for addition plumbing packages running $45,000-$130,000 depending on fixture count and slab conditions. Most Toto orders arrive within 3-5 business days, and we coordinate delivery so your plumber isn’t waiting on a toilet while framing sits exposed to Mountain View’s winter rains. Homeowners usually discover a Toto compatibility issue mid-project, when the Drake II or Ultramax II they bought online doesn’t match the 10-inch rough-in the architect spec’d, or when the Washlet+ connection kit conflicts with the wall-hung carrier the ADU plan requires.

Call (669) 215-4852

Which Toto Models This Applies To

Toto’s residential line breaks into three tiers, and each affects your addition or ADU differently. The Drake and Entrada series use standard 12-inch rough-ins and bolt-down tanks, what most Mountain View architects default to for rental ADUs because the parts are common and the flush valve (THU500) is stocked at most supply houses. The Ultramax II and Carlyle II are one-piece units with integrated tanks; they save space in a small addition bathroom but ship freight, and the rough-in tolerance is tighter, within 1/8 inch, or the skirted base leaves a gap. The Washlet+ and Neorest lines need a GFCI outlet within 3 feet and a dedicated water supply with a mini-stop valve; we’ve seen three downtown Mountain View ADU plans where the electrician missed the outlet placement and the tile had to come back up.

To identify your part, check the stamped model number inside the tank lid or on the trapway skirt, not the box label. The CST454CEFG#01 Drake II, for instance, takes a THU331 flush valve, while the MS604114CEFG#01 Ultramax II uses the THU338, and they are not cross-compatible. We source OEM Toto parts through our Ferguson and HD Supply accounts; aftermarket equivalents exist for fill valves and flappers, but we spec OEM for flush valves and carrier gaskets because the tolerance stack in a skirted bowl doesn’t forgive a 1/16-inch variance. Rowan Construction Group Mountain View is an independent service provider, not affiliated with Toto.

Signs Your Toto Home Additions & ADU Is Failing

• Phantom flushes or tank refilling every 20 minutes. The flapper seal (THU331S) is degrading, common in Mountain View where the chloramine-treated municipal water stiffens rubber faster than straight chlorine. The flapper looks fine but won’t seat flat.
• Weak swirl, incomplete bowl clearing, or need for double-flush. The rim feed holes under the bowl lip are clogging with mineral scale from the hard water that comes off the Santa Cruz Mountains aquifer. Toto’s Tornado flush depends on those jets being open.
• Water seeping from the base or staining the subfloor. The wax ring or the SmartSeal connector on a skirted bowl has failed. In an ADU over a crawl space, this can go undetected for weeks because the tenant doesn’t own the maintenance.
• Washlet+ seat losing power, heating, or spray pressure. The inline sediment filter is clogged, or the mini-stop valve’s flow restrictor is scaled shut. Both are serviceable, but the Neorest remote diagnostics require the original purchase receipt for warranty parts.
• Wall-hung bowl rocking or the carrier frame groaning. The bolts to the carrier plate have loosened, or the Geberit or Toto carrier frame was installed without shimming to the wall studs. This is structural; the frame holds 880 pounds and failure drops the fixture.

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Replacement Cost & What’s Included

The range depends on three things: whether we’re opening a finished wall to access the carrier, whether the flange needs re-poured in a slab-on-grade ADU, and whether the fixture is in stock or freight-shipped from Toto’s Morrow, Georgia distribution center. Our quote is a flat price with a written scope and a written warranty; under Clause 1 of the Haven Standard, that number is delivered before any work starts. Every visit includes a documented photo record as standard, not an upgrade. We also offer a Free Second Opinion on any written estimate, line by line, at no charge.

DIY or Call Us?

What you can safely check: the flapper chain length, the fill valve height, the supply line for kinks. These take a screwdriver and a towel. What goes wrong fast: the wall-hung carrier bolts torque to 44 foot-pounds, and over-tightening cracks the porcelain or strips the carrier insert. The skirted bowl’s SmartSeal connector requires the bowl be lowered straight down, no rotation, or the seal twists and weeps for months before it shows. We’ve been called to two Mountain View ADUs where the owner installed the carrier level to the tile instead of shimming to the studs; the bowl rocked, the tenant complained, and the repair required cutting drywall in the finished unit next door. If you’re mid-project and the Toto part doesn’t fit the rough-in, call (669) 215-4852 before the return window closes and the tile setter moves on.

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