How to Install a Dual-Flush Conversion Kit
Updated February 25, 2026
Convert any standard toilet to dual-flush with a $20-$30 kit -- half flush for liquid, full flush for solids. Saves 15,000+ gallons per year.
Overview
A dual-flush conversion kit replaces your existing flush handle and flapper with a two-button system. Press the small button for a half flush (0.8 gallons), press the large button for a full flush (1.6 gallons). Since about 80% of flushes are liquid-only, you cut water use by roughly 40%. That is 15,000-20,000 gallons per year for a family of four. The kit installs in 15-20 minutes with no special tools. You keep your existing toilet -- just swap the internals.
What You'll Need
Safety First
- Turn off the water supply before starting. The flush valve is submerged and removing it with a full tank creates a mess.
- Some conversion kits are not compatible with toilets that have a 3-inch flush valve (common on newer Kohler and American Standard models). Check the flush valve size before buying -- 2-inch is the standard that most kits fit.
Step-by-Step Instructions
- Check Compatibility
Lift the tank lid. Measure the flush valve opening (the hole at the bottom of the tank where the flapper sits). 2-inch is the standard that fits most conversion kits. 3-inch (common on toilets made after 2005) requires a 3-inch specific kit or may not be compatible. Also check the overflow tube height -- the dual-flush valve needs at least 7 inches of clearance from the bottom of the tank to the tank lid.
Tip: The Danco HYR460 and Fluidmaster 550DFRK are the two most popular dual-flush kits. Both fit standard 2-inch flush valves. The Danco works with some 3-inch valves too -- check their compatibility chart. - Remove the Old Flush Handle and Flapper
Turn off water. Flush and drain the tank. Sponge out remaining water. Inside the tank, unhook the flapper chain from the flush lever. Pull the flapper off the overflow tube ears. Unscrew the flush handle nut inside the tank -- it is reverse-threaded (turn clockwise to loosen). Pull the handle and lever arm out through the front of the tank.
Tip: Reverse thread on the handle nut trips everyone up the first time. Think: you push the handle down to flush, so the nut tightens in the opposite direction to prevent loosening during use. Clockwise to remove. - Install the Dual-Flush Valve
The conversion kit has a tower-style valve that replaces the flapper. It drops over the existing flush valve seat at the bottom of the tank. Adjust the height so the top of the tower sits about 1/2 inch below the overflow tube. The silicone seal on the bottom of the tower sits on the flush valve seat -- same spot the old flapper sealed. Press it down to verify a clean seal.
Tip: The tower valve does not hinge like a flapper. It lifts straight up when you press the button. This is why it seals better than a flapper and is less likely to develop a slow leak over time. - Install the Push-Button Assembly
The dual buttons mount through the hole where the old flush handle was. Thread the button assembly through the front of the tank. Secure with the locknut inside the tank. Connect the lift cable or chain from the button mechanism to the top of the tower valve. Adjust the cable length so the small button lifts the tower partially (half flush) and the large button lifts it fully (full flush).
Tip: Cable too long? The button will feel mushy and the valve barely lifts. Too short? The valve lifts too far on the small button and you lose the water-saving half flush. Test both buttons before filling the tank. - Fill, Test, and Adjust
Turn the water back on. Let the tank fill. Test the small button -- it should release about half the tank water and stop. Test the large button -- it should release all the tank water. If the half flush is not clearing liquid waste, adjust the cable to lift the tower slightly higher. If both buttons feel the same, the cable needs shortening for the half-flush side. Flush each button 3-4 times and check for leaks at the valve seat.
Tip: The half flush may need a few adjustments to find the sweet spot -- enough water to clear the bowl but not so much that it defeats the purpose. Most kits have an adjustment dial or specific cable hole positions for fine-tuning.
Pro Tips
- A family of four flushes about 20 times per day. At 80% half-flushes (0.8 gallons) and 20% full-flushes (1.6 gallons), you save roughly 40 gallons per day vs an old 1.6 GPF toilet. That is over 14,000 gallons per year.
- If your water rate is $5 per 1,000 gallons, the $25 kit saves $70+ per year. Pays for itself in 4-5 months.
- The push-button style looks more modern than a handle. It is a cosmetic upgrade on top of the functional one. Chrome and brushed nickel button finishes are available to match your bathroom hardware.
- Not all toilets perform well with a half flush. Elongated bowls with a siphon jet (the small hole at the front bottom of the bowl) clear waste better on low-volume flushes than round bowls without a jet.
- If the conversion kit does not clear waste on the half-flush setting, adjust the cable for a 60-70% flush instead of 50%. You still save water -- just not as much.
When to Call a Pro
You do not need a plumber for this. It is fully DIY. The only scenario where professional help makes sense is if your toilet has a non-standard flush mechanism (Kohler AquaPiston, TOTO G-Max) that the conversion kit cannot replace. In that case, buying a factory dual-flush toilet ($200-$400) is the better path.
Frequently Asked Questions
When should I call a plumber to install a dual-flush conversion kit?
You do not need a plumber for this. It is fully DIY. The only scenario where professional help makes sense is if your toilet has a non-standard flush mechanism (Kohler AquaPiston, TOTO G-Max) that the conversion kit cannot replace. In that case, buying a factory dual-flush toilet ($200-$400) is the better path.
What are some expert tips to install a dual-flush conversion kit?
A family of four flushes about 20 times per day. At 80% half-flushes (0.8 gallons) and 20% full-flushes (1.6 gallons), you save roughly 40 gallons per day vs an old 1.6 GPF toilet. That is over 14,000 gallons per year. If your water rate is $5 per 1,000 gallons, the $25 kit saves $70+ per year. Pays for itself in 4-5 months. The push-button style looks more modern than a handle. It is a cosmetic upgrade on top of the functional one. Chrome and brushed nickel button finishes are available to match your bathroom hardware. Not all toilets perform well with a half flush. Elongated bowls with a siphon jet (the small hole at the front bottom of the bowl) clear waste better on low-volume flushes than round bowls without a jet. If the conversion kit does not clear waste on the half-flush setting, adjust the cable for a 60-70% flush instead of 50%. You still save water -- just not as much.
What tools do I need to install a dual-flush conversion kit?
You will need: Dual-flush conversion kit ($20-$35, includes valve, buttons, and hardware), Adjustable wrench (for removing old handle nut), Sponge and towels (for draining residual tank water), Tape measure (to verify flush valve size and tank clearance).
When should I call a professional instead of doing this myself?
You do not need a plumber for this. It is fully DIY. The only scenario where professional help makes sense is if your toilet has a non-standard flush mechanism (Kohler AquaPiston, TOTO G-Max) that the conversion kit cannot replace. In that case, buying a factory dual-flush toilet ($200-$400) is the better path.
How difficult is this project?
This project is rated easy. Most homeowners with basic tools can complete it.
How long does this take?
Plan for approximately 15 - 30 minutes. First-timers may need extra time.
How much will this cost?
The estimated cost is $20 - $35. Costs vary by location and materials chosen.