DIY dual-flush toilet: eco-friendly and easy

Jeffrey Anderson | Improvement Center Columnist | May 7, 2013

One of the easiest methods for making your home a little more eco-friendly is to install a dual-flush toilet. Even better: it's a DIY-friendly project that can often be done without the assistance of a professional plumber.

What you need to know about dual-flush toilets

The concept behind dual-flush models is fairly simple: it shouldn't require as much water to remove liquid wastes as it does solids. Instead of a single flush setting, these fixtures have two choices available when emptying the bowl -- which you pick determines how much water is used during the flush cycle.

dual flush buttons
Dual-flush toilets offer two flush cycle buttons

dual flush feature
Three dots for liquids; nine for solids

Even if you don't live in one of the regions that have recently experienced historic droughts, using water more efficiently should be everyone's concern. Of course, if you get your water from a local utility, reduced usage could result in a lower monthly bill which is always a good thing.

Just about every major plumbing fixture manufacturer now offers eco-friendly dual-flush toilets in numerous styles and configurations. While their outer appearances may differ, most models allow you to choose between a flush that uses less than a gallon of water or the more standard 1.6 gallons.

The Sierra Club reports that a family of four may save up to 7,000 gallons of water annually by upgrading to a dual-flush toilet from a basic 1.6 gallons per flush model. If you have older fixtures in your home, the amount could be even higher.

Removing the old toilet

There's no getting around it: removing your old toilet can be an unpleasant and somewhat messy job. You may be able to limit the clean-up needed after the project by using a wet-vac to suck out any water in the tank and bowl before disassembling. If you sit the removed sections in your shower or tub to allow any remaining water to drain, that should help as well.

Jim Mallery provides an outstanding tutorial on how to remove an old toilet in an eight-part article on bathroom remodeling. Follow his steps until all that remains where the fixture once stood is the waste line flange. The flange should be PVC, or cast iron if you have an older home, and near the level of the finished floor.

Installing a dual-flush toilet

Putting in a dual-flush toilet is very similar to installing a standard model -- the primary differences are inside the tank which usually needs little attention during a new installation. The most common toilet configurations are one and two piece fixtures. A two piece model has a separate tank and bowl which must be joined together on the jobsite. A one piece toilet is manufactured with the two sections combined into a single fixture. This tutorial describes installing a two piece model, but can be used with single piece toilets as well.

Always inspect the toilet and tank after they've been unpacked from their boxes -- every once in a while they may be damaged during shipping. In many cases, all the hardware needed to install the toilet is included in the box with the exception of a new wax ring. However, it's a good idea to check before starting the project. If you need to purchase a toilet installation kit, they're available at most home improvement stores.
new dual flush toilet
Inspect fixtures for shipping damage. An extra set of eyes can be helpful.

new wax ring for toilet
Purchase a new wax ring for the project, and be sure you have an installation kit.

One item you'll definitely need to buy is a new wax ring. This is a gasket that prevents water from leaking around the bottom of the toilet bowl where it attaches to the waste line flange. When you have all the parts, follow these steps to install your dual-flush toilet:

  • Place the wax ring -- The bolts that secure the toilet bowl fit into slots in the sides of the waste line flange. Center them in the slots with the threaded sections facing upward and sit the wax ring down onto the flange. The wax should help hold the bolts in place.
    installed wax ring
  • Set the toilet bowl -- When you look at the bottom of the toilet bowl, an opening with a throat should be easily visible. This throat fits down into the wax ring and waste line opening. Line up the openings and gently sit the bowl down. When you're sure it's seated properly, apply a little downward pressure to adhere the wax around the opening.
    toilet bowl installation
    Bottom of bowl showing throat opening and holes for bolts.
  • Secure the toilet bowl -- Place the nuts on the toilet bowl bolts and tighten them down. Switch back and forth while tightening so both sides of the bowl go down gradually and at the same time. Be very careful not to over-tighten as it's possible to crack the bowl. If the bowl wobbles, you may need to loosen the bolts and install a few shims between the floor and bowl for support.
    dual flush toilet bowl
    Bowl bolted down -- large opening at rear is where the tank will be placed. The small holes are for the tank-securing bolts.
  • Set the tank-- The toilet tank should constantly contain water when the fixture is assembled. Unfortunately, there are three places at the bottom of the tank where leaks can occur. That makes it very important that the rubber washers be situated properly when attaching the tank to the bowl -- there should be one at each bolt and a large gasket at the big opening. Install the washers and gasket where needed, and sit the tank onto the bowl. Tighten the bolts gently, but securely.
    dual flush toilet tank bottom
    Bottom of tank showing gasket at large opening and washers for bolts

    inside of dual flush toilet tank
    Inside of tank showing connecting bolts at bottom. White and blue flappers are for the two flush cycles.

  • Connect the water -- The old water supply line that extends from the floor or wall can be reused with your new dual-flush toilet. Attach it to the bottom of the tank taking care to ensure it's seated correctly.
  • Turn on the water -- You should now be ready to make the toilet operable. Turn on the water at the valve on the supply line and allow the tank to fill.
  • Install the tank lid -- This dual flush toilet operates with buttons rather than a lever and in this case they're located on the tank lid. Place the lid on the tank and press one of the buttons to ensure the toilet flushes.
  • Install the seat -- Almost all toilets are sold without seats. Your old seat can be reused or you may wish to purchase a new seat. Be sure to choose a shape that fits your new fixture -- most are sold as either elongated or round.
  • Check for leaks -- You're almost sure to have a leak somewhere if this is your first toilet installation. The two most likely spots are around the bolts that hold the tank to the bowl and at the base of the fixture. In both locations tightening the bolts a little more should remedy the situation, but don't over-tighten!

dual flush toilet assembled
Assembled dual flush toilet with water line attached at rear.

Your dual-flush toilet is now ready for use. If the flushing cycle needs a little adjustment, follow the manufacturer's troubleshooting tips that should be in the installation instructions.

Dual-flush manufacturers and pricing

As mentioned above, almost all major plumbing fixture manufacturers now have dual-flush models in their line-ups. A few of the most well-known are: American Standard, Kohler, and Sterling.

Pricing varies depending on configuration, style, and color. Budget-friendly models such as the American Standard H2Option shown in the tutorial can be purchased for about $260. However, if you're looking for a unique fixture for your bathroom remodeling project, there are stylish dual-flush toilets in designer colors that can exceed $1,000.

About the Author

Jeffrey Anderson has a Degree in English from V.M.I., and served as an officer in the Marine Corps. He worked in Residential and Commercial construction management for 25 years before retiring to write full time. He spends his time writing, remodeling his old farmhouse, and in animal rescue.