Two buttons on the tank lid, one bigger than the other, and a nagging feeling that you have been pressing the wrong one for years. Dual-flush toilets have been standard in Canadian homes for well over a decade, yet they come with almost no instructions. Here is dual flush buttons explained in plain terms: what each button does, how the mechanism works, how to fix the usual faults, and when to call a plumber.
The short answer: small button for liquids, large button for solids
On nearly every dual-flush toilet sold in Canada, the smaller button (or the smaller segment of a split button) triggers the reduced flush, and the larger button triggers the full flush. The reduced flush uses roughly half the water of the full flush and is meant for liquid waste and paper. The full flush is for solid waste.
Some manufacturers use symbols instead of size: a single drop and a double drop, a half-filled circle and a full circle, or a small and a large wave. Less always means less water. On a rocker button or two-way lever, a short press or a push in one direction usually gives the reduced flush. When in doubt, lift the lid, try each one and watch the tank: the reduced flush leaves noticeably more water behind.
How a dual-flush toilet actually works
An older gravity toilet uses a flapper lifted by a chain, and every flush empties the tank. Most dual-flush toilets replace the flapper with a tower-style flush valve, often called a canister or drop valve. Pressing a button lifts the seal straight up off its seat. The two buttons lift the valve to different heights, or hold it open for different lengths of time, which controls how much water leaves before the seal closes again. Some designs add a small float to the valve that shuts it early on the reduced flush.
Under the buttons, a linkage turns your press into that lift: usually two nested plastic rods pushing on a lever arm, or on some models a pair of thin cables. Wall-hung toilets from brands such as Geberit, TOTO and Duravit put the same idea inside a concealed in-wall cistern, with a flush plate on the finished wall instead of a lid-mounted button.
Because the bowl must clear on a reduced volume, trapway shape and rim jets matter as much as the tank. A well-engineered toilet clears reliably on the small button; a bargain unit may need the full flush every time and save nothing.
Why the choice matters in Canada
Most Canadian municipalities meter residential water, and rates have been climbing from Victoria to St. John's. Toilets are usually the largest indoor water user in a home, so defaulting to the small button shows up on the bill. The National Plumbing Code of Canada includes water-efficiency requirements for fixtures, and provinces and municipalities adopt it with their own amendments, so defer to your local authority for what applies. When shopping, look for a CSA B45 or cUPC listing, which confirms the toilet meets the standards Canadian inspectors expect, and consider the WaterSense label, which caps full-flush volume and requires a bowl performance test.
Fixing the common dual-flush button problems
Most button faults come from the linkage between the button and the valve rather than the valve itself. Work through these in order.
- Button sticks or feels mushy. Remove the tank lid; the button assembly usually unscrews from underneath. Clean mineral scale from the button barrel with white vinegar and confirm the rods are seated in their lever cups and not bent.
- Both buttons give a full flush. Look for a small slider or float on the side of the flush valve, often marked with plus and minus. It sets the reduced-flush volume, and if it has been knocked to maximum the small button will empty the tank. Adjust it down in small steps and test.
- Small button barely flushes. The reverse of the above. Also check that the fill valve brings water up to the marked line on the overflow tube; low water weakens either flush.
- Toilet runs or trickles between flushes. Shut the supply valve and flush to drain the tank. Lift out the canister (most twist a quarter turn) and inspect the rubber seal at its base. Grit, scale or a hardened seal stops it seating. Clean or replace the seal, a common part for most major brands.
On well water or in a hard-water region such as much of the Prairies and parts of southern Ontario, expect scale to be the culprit more often than not. An annual vinegar soak of the seal and button barrel goes a long way.
Common mistakes
- Pressing both buttons at once. There is no super flush. Most designs simply give the full flush, and a few can jam the rods.
- Holding the button down. A short, firm press is all it needs. Holding keeps the valve open past its intended volume.
- Double-flushing the small button. Two reduced flushes usually use more water than one full flush. If it did not clear, press the large button.
- Drop-in bleach tablets in the tank. They harden rubber seals and are a common cause of running toilets. Many manufacturers exclude in-tank chemical damage from their warranties.
When to call a licensed plumber
- The toilet is wall-hung with a concealed cistern. Access is through the flush plate and the parts are brand-specific, so a plumber familiar with in-wall systems will save you a headache.
- You have replaced the seal and adjusted the valve and it still runs. The valve seat or a hairline tank crack may be the real problem.
- Water is appearing at the base of the toilet. That is a wax ring or supply issue, not a button issue, and it damages subfloor quickly.
- You are replacing the whole toilet, or winterizing one in a seasonal property. In many provinces plumbing is a licensed trade and some municipalities require a permit for fixture replacement. A cottage toilet in Muskoka, the Laurentians or the Kootenays holds water in the tank, trapway and fill valve that must be drained or protected before the first hard freeze.
Related products worth a look
If you are replacing rather than repairing, the dual-flush toilet collection covers one-piece, two-piece and wall-hung options from TOTO, Kohler, Duravit, Geberit, Icera, Caroma and others, shipped across Canada. If you would rather not think about buttons at all, smart toilets often flush automatically after use. Contractors can join the trade program, and for more buying advice, browse the Vatero guides hub.
Frequently asked questions
Which button is the half flush on a dual-flush toilet?
The smaller button, or the smaller segment of a split button, is almost always the reduced flush. With symbols, the single drop or half-filled shape is the reduced flush. Watch the tank level if you are unsure.
Does the small flush still save water if I occasionally need to flush twice?
Yes. One full flush when needed still uses less water over a week than pressing the large button every time. If you regularly need two flushes for liquid waste, the tank water level or valve adjustment is probably off.
Can I convert my old single-flush toilet to dual flush?
Retrofit dual-flush valve kits fit many standard two-piece tanks, but results vary because the bowl was never designed to clear on a reduced volume. If water savings are the goal, a purpose-built dual-flush toilet with a CSA or cUPC listing will perform better.
Are dual-flush toilets required by code in Canada?
Not specifically. The National Plumbing Code of Canada sets water-efficiency requirements for fixtures, and dual flush is one way to meet them, but single-flush high-efficiency toilets also qualify. Check your provincial code or municipal building department for what applies.
