Gerber Toilet Fill Valve and Flapper Replacement

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Quick answer from a licensed plumber: For the fill valve, Gerber makes one part for all its gravity toilets: the GA711048 Universal Fill Valve. You set its height and flow restrictor for your tank number. Flappers are model-specific: Gerber’s parts list for the Viper 1.6 gpf (tank GVP38590) names flapper GA715067, and Gerber’s dual flush toilets have no separate flapper at all. Find the tank number on the back wall inside the tank, near the water line.

Replacing a Gerber fill valve? Gerber’s own universal part is the GA711048. See the Gerber GA711048 on Amazon

Gerber Toilet Parts at a Glance

The fill valve is the easy part: Gerber makes one universal valve for its gravity toilets. Flappers are model-specific. The Viper’s product page on gerber-us.com links an Illustrated Parts List that names the exact flapper, so look for the same document on your model’s page.

Step 1: Find the Tank Item Number

Gerber says the model number of a two-piece tank is “on the back wall inside the tank, near the water line,” along with the cast date and a bar code and serial number (the D & S code). On a one-piece toilet it is in the same place. The bowl has its own number under the rim, so do not mix the two up: the parts you need for a running toilet follow the tank.

Older Gerber 1.6 gpf tanks have numbers in this style, per Gerber:

Step 2: Test the Flapper Before You Buy

Gerber’s test: first make sure the chain has a little slack and is hooked to the tank lever so it lifts the flapper fully. Then “pour a bit of food coloring into the toilet tank water” and check back in 15 minutes. If the bowl water has changed color, the flapper most likely needs replacing. If a new flapper does not stop it, Gerber says the whole flush valve may need replacing.

Gerber also says to look at what the flapper seals against. With the flapper off, check the flush valve’s seat for damage or warping; if the seat is damaged, a new flapper will not seal and the flush valve assembly has to be replaced.

Step 3: Replacing the Fill Valve

Gerber’s Universal Fill Valve, GA711048, is the one to buy for a Gerber gravity toilet. Gerber says it fits Viper, Avalanche, Maxwell and more, and it comes with every flow restrictor. The two settings that are specific to your tank are the valve height and the refill restrictor color. Gerber’s Fill Valve Info page on gerber-us.com takes your tank item number and gives both.

1. Close the shutoff, flush and sponge out the tank.
2. Disconnect the refill tube from the overflow tube, remove the coupling nut and the locking nut, and lift out the old valve.
3. Set the new valve’s total height and float position to the dimensions for your tank.
4. Install it and tighten the locking nut; Gerber gives 5 to 8 ft-lbs (60 to 96 in-lbs).
5. Fit the colored refill restrictor for your tank model and clip the refill tube so it flows directly into the overflow tube.
6. Turn the water on and adjust so the tank fills to the water line marked on its back wall.

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Slow Fill? Check These First

Gerber says a single flush 1.6 or 1.28 gpf tank generally fills in 30 to 60 seconds. If yours takes longer, Gerber’s list is: the supply valve fully open, the water level set to the line, the flapper sealing (“a flapper that is not meant to go with your toilet tank may cause your toilet tank to take longer to fill”), and debris in the fill valve. On some valves Gerber shows pulling a small filter out of the fill valve shaft with needle-nose pliers to clean it, for example the GA711044 used in certain Maxwell tanks.

What to Buy

The genuine Gerber fill valve, plus a flapper option:

• Fill valve: Gerber GA711048 Universal Fill Valve, sold by Gerber Plumbing Fixtures and shipped by Amazon. Its listing says one valve is designed to fit all Gerber gravity-fed toilets.
• Flapper for a 3-inch Gerber flush valve, aftermarket: Fluidmaster 5403 universal 3-inch flapper, sold by Amazon. Its listing says it “fits most 3-inch flush valve toilets” and is not for 2-inch valves. It is not a Gerber part and Gerber does not list it, so compare it with your old flapper. We did not find the genuine GA715067 shipped or sold by Amazon when we checked; Gerber’s parts line is 1-888-648-6466.

For a Gerber Dual Flush Tank

Only for the dual flush tanks Korky names:

• A dual flush seal, if yours is a Gerber dual flush tank on Korky’s chart: Korky 444 Dual Flush Seal D, sold by Amazon. Korky’s listing says it fits Gerber tank models DF-29-530, DF-28-528 and DF-28-190 with flush valve model B4200. It is a Korky part, not a Gerber part.

When to Call a Licensed Plumber

• Gerber’s test says the flush valve itself is the leak, which means taking the tank off the bowl.
• Both the toilet and the tub fill slowly. Gerber says that means your bathroom water system has low pressure, not a toilet problem.
• The shutoff valve will not close.

FAQ

What fill valve does a Gerber toilet use?

Gerber makes one Universal Fill Valve, GA711048, that it says fits all Gerber gravity-fed toilets, including Viper, Avalanche and Maxwell. Set its height and refill restrictor color for your tank using Gerber’s Fill Valve Info page.

Where is the model number on a Gerber toilet tank?

On the back wall inside the tank, near the water line, per Gerber, with the cast date and a bar code and serial number. The bowl’s number is separate, under the rim.

What flapper does a Gerber Viper use?

Gerber’s parts list for the Viper 1.6 gpf GVP31502 series, tank GVP38590, lists flapper GA715067, with fill valve GA711048 and flush valve GA712032. Other Viper tanks may differ, so check your tank’s parts list.

How do I test a Gerber flapper for a leak?

Put a little food coloring in the tank and wait 15 minutes, per Gerber. If the color shows up in the bowl, the flapper most likely needs replacing. Check that the chain has slack and lifts the flapper fully before you test.

How long should a Gerber toilet take to refill?

Gerber says a single flush 1.6 or 1.28 gpf tank generally takes 30 to 60 seconds. Longer than a minute points to a partly closed supply valve, a leaking or wrong flapper, debris in the fill valve or low house pressure.

Why Trust Plumbing Picks

Plumbing Picks is written by a licensed Georgia journeyman plumber. Every part number, size and fit on this page comes from the manufacturer pages and documents listed below, which we opened and read; product details come from those makers and from the Amazon listings, not from hands-on testing. Each linked product was shipped or sold by Amazon, new and in stock, when we checked on September 24, 2026. Nobody pays to be included here. Where a link goes to Amazon we may earn a commission at no extra cost to you. More on who writes this and how we pick.

Sources

• Gerber: Where Can I Find The Model Number For My Gerber Product?
• Gerber: How can you identify an old Gerber 1.6 Gravity Toilet Tank Collection?
• Gerber: How to test toilet flapper for a leak?
• Gerber: My Toilet Flush Valve Does Not Close Properly
• Gerber: How Do I Remove and Replace The Fill Valve from a Toilet Tank?
• Gerber: Fill Valve Info (height and restrictor lookup)
• Gerber: Universal Fill Valve for Gerber Toilets, GA711048
• Gerber: What should I do if my toilet tank is refill slowly than usual?
• Gerber: GA711044 fill valve filter for Maxwell tanks
• Gerber: Viper 1.6 gpf two-piece elongated toilet, GVP31512
• Gerber: Viper GVP31502 series Illustrated Parts List

Bottom Line

Read the tank number, run Gerber’s food-coloring test, and buy the part it points to: the GA711048 fill valve for any Gerber gravity toilet, or the flapper named on your tank’s parts list. Dual flush tanks take a seal, not a flapper.