Zurn Z5551-K Toilet Review
A research-based look at the Zurn Z5551-K: a commercial-grade 1.6 gpf, two-piece, ADA-height elongated siphon-jet toilet with a 3-inch flush valve and 2-1/8-inch trapway.
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The Zurn Z5551-K is a two-piece, vitreous china toilet with an elongated, ADA-height bowl that flushes with 1.6 gallons through a 3-inch flush valve and a siphon-jet bowl. Zurn markets the model for commercial spaces, and the spec sheet reflects that: chloramine-resistant internal parts, a concealed sanitary bar and an extra-large footprint for retrofits. For a home, its main drawback is water use, since 1.6 gpf is the federal maximum rather than a high-efficiency rate.
This review is based on Zurn’s product page, specification sheets and installation instructions. We have not physically tested the Z5551-K; our methodology page explains how we research products.
Status as of November 2026: The Z5551-K is current. Zurn’s website has a product page for it, and Zurn’s spec sheet for the model was revised in December 2025. It is also listed at Home Depot. Note that an older model without the -K suffix (Z5551) is listed as discontinued by some sellers, so make sure the number ends in -K.
Zurn Z5551-K specifications
These figures come from Zurn’s two spec sheets (revised August 2022 and December 2025) and the installation guide.
Zurn Z5551-K specifications
| Brand | Zurn |
|---|---|
| Model | Z5551-K |
| Bowl shape compatibility | Elongated; ADA height (16-1/2 in. rim per 2025 spec sheet) |
| Seat material | Vitreous china |
| Heated seat | No |
| Bidet features | No |
| Water heating | 1.6 gpf (6.0 Lpf), gravity siphon jet |
| Warm-air dryer | No |
| Installation requirements | 12 in. rough-in |
| Power requirements | None |
| Warranty | 3-year limited |
| Dimensions | Unverified |
| Feature | What Zurn lists |
|---|---|
| Construction | Two-piece, vitreous china |
| Bowl | Elongated front rim, ADA height |
| Rim height | 16-1/2 in. (2025 spec sheet); the 2022 sheet lists 16-23/32 in. |
| Flush rate | 1.6 gpf |
| Flushing system | Gravity, ZURN-HPT high-performance siphon jet |
| Flush valve | 3 in. |
| Trapway | 2-1/8 in., fully glazed |
| Trap seal | 2-1/2 in. |
| Water surface | 9 x 11 in. |
| MaP (manufacturer-listed) | 1,000 g |
| Rough-in | 12 in. |
| Seat | Sold separately (Zurn recommends its Z5958SS-EL closed-front seat) |
| Other | Chloramine-resistant internal parts, chrome-plated metal handle, concealed sanitary bar, bolt caps included |
| Shipping weight | 92 lb |
| Warranty | 3-year limited (Zurn product page) |
| WaterSense | No; 1.6 gpf is above the 1.28 gpf WaterSense limit |
Design and flushing system
Siphon jet with a 3-inch valve
The Z5551-K is a gravity toilet. When you press the handle, water drops from the tank through a 3-in. flush valve into the bowl, and a jet at the bottom of the bowl pushes water into the trapway to start the siphon that pulls waste out. Zurn calls this its HPT (High Performance) design. The 2-1/8-in. trapway is fully glazed inside, which reduces friction for waste moving through it.
Built for commercial conditions
Several details point to the model’s commercial roots. Zurn lists chloramine-resistant internal components. Some water utilities use chloramine as a disinfectant, and Zurn calls out these parts specifically to resist it. The concealed sanitary bar and chrome-plated metal handle are durability and cleanliness touches you see on fixtures meant for public restrooms. The extra-large footprint helps cover the outline left by an old toilet.
ADA height
Zurn’s spec sheet says the toilet meets ADA and ANSI A117.1 requirements when installed according to those standards. The ADA Standards set seat height at 17 to 19 in., measured to the top of the seat, so the seat you choose matters. Zurn’s 2025 sheet adds that not every combination of options will comply, and suggests contacting Zurn’s customer care if you need confirmation for a particular project.
What we like
- 3-in. flush valve and siphon-jet bowl with a 1,000 g manufacturer-listed MaP result
- 2-1/8-in. fully glazed trapway and 2-1/2-in. trap seal
- ADA-height elongated rim
- Chloramine-resistant internal parts
- Large footprint for retrofits
Things to consider
- 1.6 gpf uses more water than 1.28 gpf models and is not WaterSense
- Seat sold separately
- 3-year warranty is shorter than the lifetime chinaware coverage some residential models list
- Utilitarian styling
- 12-in. rough-in only; Zurn's sheet says not to use its dimensions for pre-plumbing
Z5551-K vs Zurn’s related models
Zurn’s 1000g two-piece toilet sell sheet groups the Z5551-K with two siblings that share the same 1.6 gpf tank and siphon-jet bowl system, and with 1.28 gpf EcoVantage models.
| Model | Flush rate | Bowl | Height | Water surface |
|---|---|---|---|---|
| Z5551-K | 1.6 gpf | Elongated | ADA | 9 x 11 in. |
| Z5552-K | 1.6 gpf | Elongated | Standard | 9 x 11 in. |
| Z5553-K | 1.6 gpf | Round front | Standard | 9 x 11 in. |
| Z5555-K | 1.28 gpf | Elongated | ADA | 10 x 8 in. |
The sell sheet dates from 2015, so check each model’s current Zurn page before ordering. Zurn’s site has a current product page for the Z5555-K, a 1.28 gpf elongated high-efficiency siphon-jet toilet.
Installation notes
Zurn’s installation instructions cover the Z5551-K, Z5552-K and Z5553-K together. The process is the familiar two-piece sequence: remove the old toilet and scrape off the old wax, test-fit the floor T-bolts and cut them to length, place a new wax gasket on the bowl outlet, set the bowl, then mount the tank and connect a 3/8-in. supply with a shutoff valve if the installation is new.
Two details stand out. Zurn warns repeatedly not to overtighten the floor or tank nuts, because the china can break or chip. And the tank nuts should be tightened evenly until the tank touches the front and back sanitary bars on the bowl shelf, then stop. The fill valve is factory set to 1.6 gpf. If you are unsure about the flange or shutoff valve, call a licensed plumber.
Who it’s for
- Light-commercial and heavy-use spaces such as offices, shops, garages and rental units, where durability matters more than styling.
- Homes on chloraminated water that have had trouble with tank parts wearing out.
- Anyone who needs an ADA-height elongated bowl at a standard 12-in. rough-in. Our bathroom accessibility guide covers grab bars and other changes that go with it.
It is a weaker fit for a primary bathroom where water efficiency or appearance is a priority. A 1.28 gpf toilet will use less water every flush; our water estimator can show the difference for your household.
What to check before you buy
- Local water rules. 1.6 gpf meets the federal limit, but some states and cities set lower limits for new toilets. Check with your local building department or plumber.
- Model suffix. Confirm “Z5551-K,” not the older Z5551 or the standard-height Z5552-K.
- Rough-in. Measure 12 in. from the finished wall to the center of the floor bolts.
- Seat. Budget for an elongated seat. Zurn recommends a closed-front seat with a stainless steel check hinge, and its installation guide advises a self-sustaining seat with check hinges for extra-heavy-duty plastic seats, to protect the rim.
- Cleaners. Zurn’s installation guide warns that in-tank toilet bowl cleaners void the warranty on Zurn toilets.
- Weight. At a 92 lb shipping weight, plan for two people to carry and set it.
Frequently asked questions
Is the Zurn Z5551-K discontinued?
No. As of November 2026, Zurn’s site lists it and its spec sheet was revised in December 2025. Some sellers list the older Z5551 (without -K) as discontinued, which is a different listing.
Is the Z5551-K WaterSense certified?
No. It uses 1.6 gpf, and WaterSense toilets must use 1.28 gpf or less. Zurn’s Z5555-K is a 1.28 gpf alternative.
Does the Zurn Z5551-K include a seat?
No. Zurn’s installation guide lists the toilet seat as sold separately. Zurn recommends its Z5958SS-EL elongated closed-front seat.
What warranty does the Z5551-K have?
Zurn’s product page lists a 3-year limited warranty, consistent with the three-year term Zurn’s general terms give for commercial fixtures.
Bottom line
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