The Gerber 28-590 is a common older Viper toilet tank, but replacing its lid can be less straightforward than typing “28-590 lid” into a search box. Similar model numbers, different production versions, and listings that use either the tank number or lid number can make two different parts look like the same replacement.
If your toilet is a Gerber Viper, use the tank markings, rough-in, measurements, and underside shape together before ordering.
What is the Gerber 28-590?
Gerber identifies the 28-590 as a Viper 1.6 GPF tank with a 12-inch rough-in. In Gerber's older 1.6 GPF Viper family, related tank numbers include 28-592 for an insulated 12-inch tank, 28-594 for a 14-inch rough-in, and 28-595 for a 10-inch rough-in.
That means the “28-590” marking is primarily a tank model number. Replacement lids are often described using the TC-28-590 designation.
Where to find the model number
Remove the lid carefully and inspect the inside walls of the tank. Look for Gerber branding and numbers in the ##-### format. If the original lid is available, inspect its underside as well.
Do not rely only on the bowl number. Gerber's Viper 1.6 GPF family used separate bowl numbers, including 21-552 for a round-front bowl and 21-562 for an elongated bowl. The tank number is the more useful starting point when you are replacing the tank lid.
Why “28-590” alone may not be enough
FixALid has encountered more than one physical lid profile associated with 28-590-family replacement searches. To reduce wrong-fit orders, we catalog those physical profiles separately instead of assuming every lid marketed under the same family terminology is interchangeable.
Our current catalog separates them as:
- Gerber 28-590 Version 1 — the older, larger profile in our catalog.
- Gerber TC-28-590 Version 2 — a smaller profile that must be matched separately.
“Version 1” and “Version 2” are FixALid catalog labels used to distinguish the physical lids we have documented; they should not be treated as official Gerber generation names.
Check the rough-in
The rough-in is the distance from the finished wall behind the toilet to the center of the floor bolts. Gerber lists the 28-590 as a 12-inch rough-in tank.
This is useful because neighboring Viper tank numbers can represent different rough-ins or insulated versions. If the tank marking is hard to read, the rough-in is another clue—but it still should not replace a direct tank-number match.
Measure before ordering
Measure both the tank opening and the original lid when possible. Record the maximum left-to-right width and front-to-back depth. A difference of even a fraction of an inch can matter if the underside lip or locating feet do not line up with the tank.
Also compare:
- front-edge curve,
- rear-edge shape,
- corner radius,
- underside ribs,
- ceramic feet or locating tabs, and
- any molded or inked numbers underneath.
Photos are often more useful from underneath
A top photo may show a plain white rectangle. An underside photo shows the structure that actually keeps the lid centered on the tank.
For a Gerber 28-590 identification, a useful photo set includes:
- the complete toilet from the front,
- the markings inside the tank,
- the top of the old lid,
- the underside of the old lid, and
- measurements with the tape visible.
Do not use color as the primary identifier
Gerber produced toilets in more than one finish. White and biscuit lids can share the same basic shape, while two white lids can belong to different tanks. Confirm the physical fit first and the finish second.
Gerber 28-590 replacement checklist
Before buying, confirm as many of these as possible:
- Brand: Gerber
- Tank family: Viper
- Tank marking: 28-590 if present
- Rough-in: 12 inches for the standard 28-590 tank
- Lid profile: compare top and underside photos
- Measurements: compare the actual lid and tank opening
- Color: confirm only after the model match
The goal is not to find a lid that merely looks close. It is to identify the exact physical cover that seats correctly on your tank. FixALid keeps separate listings when we find meaningful physical differences so shoppers have more information before ordering.