A dual flush toilet is a type of toilet designed with two flush buttons or handles to allow for a choice between two flush volumes – a full flush for solid waste removal or a partial flush for liquids. Dual flush toilets provide the flexibility of using the water volume required for the specific flush need, helping to conserve water.
How Does a Dual Flush Toilet Work?
Dual flush toilets have two flush mechanisms and buttons/handles to activate either a full or partial flush. Here is how they work:
Full Flush
- Activating the full flush button opens both the full flush and partial flush valves in the tank. This releases the maximum amount of water stored in the tank into the bowl – usually around 1.6 gallons (6 liters) for the high-efficiency models.
- The full volume of water creates a strong siphon effect and forceful flush action to effectively clear solid waste and fully rinse the bowl.
Partial Flush
- Activating the partial flush button opens only the smaller valve in the tank. This releases around 0.8-1.1 gallons (3-4 liters) of water into the bowl.
- The lesser water is still enough to rinse liquid waste, light toilet paper and other light debris through the trapway without clogging. The reduced water helps save water.
- Some models have only a single flapperless valve that releases partial or full flush volumes based on which button is pressed.
Summary
- Full flush button releases full tank volume for maximum bowl rinse.
- Partial flush releases smaller amount just to rinse liquids and light waste.
- Dual valves or flapperless valve allows choice between two flush volumes.
What Are the Benefits of a Dual Flush Toilet?
Installing a dual flush toilet offers several benefits:
Saves Water
- Dual flush toilets save water by allowing a partial flush for just liquids using 0.8-1.1 gallons per flush. The Environmental Protection Agency estimates this saves nearly 13,000 gallons per year for a family of four compared to an inefficient 3.5 GPF toilet.
- The full flush volume is also just 1.6 GPF for dual flush high efficiency toilets, which still saves 30% over outdated 3.5 GPF models. The combined water savings are significant.
Lower Utility Bills
- The water savings from dual flush toilets directly translates into lower utility bills and water expenses over time. The more occupants in a home, the more potential savings.
High Efficiency
- Dual flush toilets meet the latest high efficiency standards for water conservation and performance. Their effective siphon flushing action also keeps the bowl cleaner.
Cleaner Bowl
- The two flush options help optimize bowl rinsing for waste type and reduce the need for double flushing. Less waste residue means a cleaner bowl.
Environmentally Friendly
- Dual flush toilets reduce residential water waste and anthropogenic water use, which is important for environmental sustainability, especially in drought-prone regions.
What Are the Parts of a Dual Flush Toilet?
Dual flush toilets consist of several components:
Toilet Bowl
- Elongated or round front bowl to accept and rinse away waste. Some models have a shrouded (concealed) trapway.
Tank
- Storage tank mounted behind the bowl. Holds fresh water to be released for flushing.
Dual Flush Valves
- Two interconnected flush valves (or flapperless assembly) that release partial and full volumes of tank water.
Actuation Buttons/Handles
- Buttons or handles on the tank top or side to manually activate partial and full flush.
Float Ball/Sensor
- Regulates water level and refills tank after a flush.
Flush Pipe
- Carries water from tank to bowl.
Drain Trap
- Curved waste passage behind bowl. Keeps sewer gases out of bathroom.
How Much Water Do Dual Flush Toilets Use?
The flush volumes for dual flush toilets are:
- Full flush – 1.6 gallons (6 liters). Provides full force siphon rinse.
- Partial flush – 0.8-1.1 gallons (3-4 liters). Saves water for just liquids.
- Total daily avg. – 16.6 gallons, assuming 5 full flushes and 5 partial flushes.
For comparison, non-efficient 3.5 GPF toilets use 3.5 gallons per flush and 56 gallons daily for 10 flushes. So dual flush toilets save over 30,000 gallons per person each year!
What are the Different Types of Dual Flush Toilets?
There are several design styles and installation types for dual flush toilets:
Two-Piece Toilets
- Toilet bowl and separate tank mounted behind the bowl. Most common dual flush design.
One-Piece Toilets
- Bowl and tank fused into single vitreous china unit. Sleeker style, easier cleaning.
Wall-Hung Toilets
- Bowl mounts directly to wall bracket. Tank mounts separately or is concealed. Space saver.
Floor-Mounted Toilets
- Toilet installed directly onto floor flange. No separate tank. Used with macerating toilets.
Round or Elongated Bowl
- Round bowls are more compact. Elongated bowls are oval-shaped for comfort. Both available.
Gravity Flush vs Pressure Assisted
- Gravity flush relies on siphon action to rinse bowl. Pressure assisted uses compressed air in tank to increase flush power. Both options available.
What Are the Best Dual Flush Toilet Brands?
Some of the best brands for dual flush toilets are:
- Toto – Industry leader. Renowned for innovation, quality, and reliability. Broad dual flush model range.
- Kohler – Excellent designs, durable finishes, and reliable flushing systems. Numerous dual flush options.
- American Standard – Offers Champion, Cadet, and VorMax dual flush model lines with excellent value.
- Woodbridge – Budget-friendly option. Simple contemporary styles. Good performance for the price.
- Swiss Madison – Stylish contemporary dual flush toilets. European-designed. Good range of models.
- Niagara – Known for very high-efficiency 0.8/0.4 GPF Stealth model. Effective siphon bowl rinse.
What Should You Look for When Buying a Dual Flush Toilet?
Key criteria to evaluate when selecting a dual flush toilet:
- Water usage – Lower is better. 0.8/1.6 GPF or 0.8/1.28 GPF are good options.
- Bowl shape – Round or elongated to suit bathroom space and comfort needs.
- Bowl rinse – Ensure the full flush provides a powerful siphon for clearing waste.
- Valve design – Well-engineered dual flush valves are critical for reliability.
- Flush ratings – Look for high MaP flush scores (grams of waste cleared).
- Style – Match toilet style to your existing bathroom decor.
- Comfort height – Ideal seat height is 16-19 inches for easy sitting and standing.
- Warranty – At least 1 year on porcelain and 5 years on parts.
How Do You Install a Dual Flush Toilet?
Here is an overview of dual flush toilet installation:
Turn Off Water Supply
- Turn off toilet supply valve and flush tank empty. Towel up any residual water.
Remove Old Toilet
- Disconnect and remove supply line. Unbolt toilet from floor and remove it.
Install New Toilet
- Set bowl on flange. Insert bolts through base holes and tighten nuts.
Install Tank
- Lower tank onto bowl bolts. Hand tighten nuts under tank. Attach supply valve.
Connect Water Supply
- Connect supply line to valve and turn on water. Fill tank and check for leaks.
Seal Toilet Base
- Apply new wax ring seal between bowl outlet and drain flange.
Adjust Toilet
- Adjust tank bolts to level bowl and allow proper flushing.
How Do You Fix a Dual Flush Toilet?
Common dual flush toilet repairs include:
Partial Flush Not Working
- Clean or replace flush valve seal. Check chain/lever activation. Clear obstructions under small flush valve.
Full Flush Poor Performance
- Clean flush valves, siphon holes. May need flush valve replacement. Remove obstructions in trapway.
Toilet Leaking
- Replace cracked tank components. Clean or replace flush valve seal. Tighten loose bowl bolts.
Toilet Won’t Fill
- Adjust or replace fill valve. Clear obstructions under float cup. May need new flapper flush valve.
Noisy Tank Refill
- Adjust water level. Clean fill valve. Replace fill valve if worn.
Water Trickling Into Bowl
- Clean or replace flush valve seal. Check chain/lever not sticking. Replace valves if worn.
Frequently Asked Questions
What is the best dual flush toilet?
Some top choices are the Toto Drake II, Kohler Highline Classic, and American Standard Champion 4. All provide excellent water savings along with robust flushing performance.
How do you flush a dual flush toilet?
Press the full flush button or lift the handle fully for solid waste. Press the partial flush button or lift the handle slightly for just liquids.
Do dual flush toilets clog easily?
No. Their siphon jet action creates a strong rinse. But very large masses or excessive TP can clog any toilet. Proper use helps prevent clogs.
Do dual flush toilets save money?
Yes, a dual flush toilet can save a family of 4 over $100 per year on their utility bills by reducing water usage by 30% or more.
Can you convert a regular toilet to dual flush?
It is generally not possible. The tank and inner workings would need complete replacement. Easier to install a new dual flush toilet designed for the purpose.
Conclusion
Dual flush toilets provide flexible flush options and significant water savings compared to regular 1.6 GPF or older 3.5 GPF toilets. Their two button or handle system allows a light flush just for liquids or a full flush for solid wastes. Dual flush toilets employ precision-engineered dual valves to control the two flush volumes. Top models provide robust siphon flushing action while using just 0.8-1.6 gallons per flush. When shopping, look for efficient water usage, an elongated bowl, quiet operation, and a reliable warranty from a reputable brand. With proper installation and maintenance, a dual flush toilet can provide many years of optimal water conservation and waste clearing performance.