Toto Home Additions & ADU Nationwide

Toto Home Additions & ADU: The Chula Vista Owner’s Guide

Toto fixtures in Chula Vista home additions and ADUs typically run $450-$1,200 per bathroom install, with full ADU plumbing packages from $8,500-$18,000 depending on fixture count and rough-in complexity. We stock Toto Ultramax II, Drake II, and Washlet-compatible valves and flappers on our Chula Vista trucks, and we can usually source same-day for less common Toto commercial-grade units. Most homeowners realize there’s a problem when the Toto toilet in their new addition runs continuously, the Washlet seat loses heating, or the pressure-assisted flush weakens after the first year of use.

Call (619) 536-0571

Which Toto Models This Applies To

Toto’s residential line breaks into three tiers that matter for Chula Vista additions and ADUs. The entry-level Drake and Entrada series use standard 2-inch flush valves with 3-inch outlets, easy to match. The mid-grade Ultramax II and Carlyle II use Toto’s proprietary Double Cyclone (now Tornado Flush) system with a 2.125-inch flush valve that requires the THU331 valve-and-flapper assembly, not a generic 2-inch replacement. The integrated Washlet models, G400 and G500, carry a dedicated inline water filter and a heated-seat circuit that fails in coastal humidity if the bathroom venting is undersized.

To identify your part, lift the tank lid and check the stamped model number inside the bowl rim or on the underside of the tank lid. The ST number (like ST743S) is the tank; the CST number is the complete toilet. For Washlets, the model is on a label under the seat hinge. We carry OEM Toto parts and quality equivalents from Korky and Fluidmaster where the spec matches, but we won’t substitute a generic flapper on a Tornado Flush unit, the seal geometry is wrong and it will leak in six weeks.

Signs Your Toto Home Additions & ADU Is Failing

• Continuous running or phantom flushing. The flapper or flush valve seal has hardened. In Chula Vista, the combination of municipal water chloramine and summer tank temperatures above 80 degrees degrades rubber faster than the manufacturer rates for.
• Weak flush despite full tank. The fill valve (typically a TSU99A.X on newer Toto models) is delivering water too slowly, or the rim feed holes are clogged with scale from the Otay Water District’s moderately hard supply.
• Washlet seat not heating or spraying cold. The inline strainer is clogged, or the thermistor has failed. We see this in ADUs where the owner skipped the dedicated GFCI circuit Toto specifies.
• Water pooling at the base. The wax ring or the Toto-specified rubber gasket has compressed, or the closet flange was set too low during the original rough-in, a mistake we catch often in additions where the plumber rushed the slab pour.
• Handle loose or tank rocking. The mounting bolts have corroded, or the china has micro-cracked from overtightening during install. Toto tanks use specific bolt spacing; a universal bolt kit won’t seat flat.

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Replacement Cost & What’s Included

For Toto fixture repair and replacement in Chula Vista additions and ADUs, here is what we quote in writing before work starts:

The range depends on access (crawl space vs. slab), whether we need to modify the rough-in for a different Toto model, and if the shutoff valve needs replacement. Every quote is flat price with written scope. Under Clause 1 of the Haven Standard, that number does not change unless you sign a change order. Our 365-Day Done Right Promise covers the workmanship; Toto’s manufacturer warranty covers the china and electronics.

DIY or Call Us?

Here’s where the line sits. A homeowner can safely shut off the angle stop, sponge the tank, and check whether the flapper chain is kinked or the fill valve float is stuck. That takes ten minutes and a towel.

What goes wrong past that point: the Tornado Flush valve nut is reverse-threaded and cracks the tank if you torque it standard direction. The Washlet seat has a live water connection and a 120V circuit within inches of each other; we have seen homeowners bridge that gap with a metal screwdriver and trip every GFCI in the ADU. And if you’re replacing a toilet in a new addition, the flange height relative to the finished floor determines whether you seal properly or rot the subfloor in two years. We pull permits for ADU plumbing modifications, pass inspection, and document the photo record so you have evidence of proper flange setting and venting. For Toto work in Chula Vista, call (619) 536-0571 and we’ll schedule a free estimate with the written price.

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