What's the deal with low-flow and dual-flush toilets?

flush buttons
Dual-flush toilets were invented in Australia and use more water when they're flushing solid waste.

Once upon a time -- in the United States, anyway -- we didn't have much choice when we were in the market for a new toilet. Did we want the white porcelain model that used 7 gallons of water per flush ... or the other white porcelain model that used 7 gallons of water per flush? If you were lucky you might be able to find one that used 3.5 gallons. That all changed in 1992, when the Federal Energy Policy Act decreed that new toilets sold in the U.S. could use no more than 1.6 gallons of water per flush.

The law was an environmentally sound policy, for sure, but consumers were none too happy with their new toilets when it went into effect in 1994. The low-flow models didn't flush quite as efficiently as the old ones, with many people reporting that they had to flush twice to get everything down the pipes. But over the years the designs and flushing mechanisms were streamlined, and now you'd be hard-pressed to tell the difference between a low-flow and a water-guzzler. You will see a difference in your water bills, though; according to the Environmental Protection Agency, low-flow toilets will decrease your water bills by about $100 a year.


Most low-flow toilets are indistinguishable from old-school models, but if you've traveled internationally you might have seen a toilet with a two-section push-button flusher. These are dual-flush toilets that were invented in Australia -- they use more water when they're flushing solid waste. They haven't quite caught on in the United States, though, but the tide is definitely turning in favor of high-efficiency toilets.

Benefits of Low-Flow Toilets

There's really nothing not to like about low-flow toilets. To the naked eye, there's absolutely nothing that differentiates them from the traditional toilets we all know and love. For the most part, they're identical -- same size, same shape, same plumbing fittings, same flushing apparatus. But the inner workings are newfangled and more efficient -- which is what really matters. After the debacle of the 1990s, low-flow toilets now work just as well as their gallon-guzzling forebears.

The benefits issue is basically moot, anyway, because we don't exactly have a choice about toilets these days. You can't buy gallon-guzzling models anymore, so our purpose here is not to convince you to buy a low-flow toilet. The low-flow law was decreed long ago, and now it's the only option out there. So unless you live in an older home with original toilets, low-flow it is -- and low-flow is good.


If you do have to buy a low-flow toilet -- either for a new home or as a replacement for an older model -- many municipalities offer rebates and incentives for them, usually in the neighborhood of $100 each. So if you're still watching 7 gallons swirl down the tubes every time you flush, there's really no reason not to switch. You'll be helping the environment and your wallet to boot!

Benefits of Dual-Flush Toilets

There's really no downside to dual-flush toilets, either. They use about .8 gallons per flush for liquid waste and the standard 1.6 gallons for solid matter, a concept that makes total sense -- we actually wonder why it took this long to implement it. The American Water Works Association says that the average dual-flush user flushes 4.8 gallons per day, as opposed to 8 gallons for toilets that use 3.5 gallons per flush. When you compare a dual-flush to a conventional low-flow toilet, the dual-flush uses about 25 percent less water.

Because your annual water bill will decrease by about $100 (or more with a dual-flush), investing $100 to $300 in a high-efficiency toilet is actually a money-saving endeavor. And when you take into account that installing a low-flow or dual-flush toilet is no more difficult than installing a traditional toilet, the decision becomes even more of a no-brainer.


If you still don't want to shell out the money for a new toilet, there are plenty of DIY options for making your old porcelain throne into a low-flow. All you have to do is take a sand- or pebble-filled half-gallon plastic jug and sink it in your toilet tank -- this will save you a half-gallon per flush. You can also buy extremely inexpensive, easy-to-install converter kits that can make your toilet into a dual-flush in a matter of minutes.

So, now that you know the ins and outs of low-flows and dual-flushes, there's really no reason not to take the plunge and buy one already! On the next page you can learn more about the inner workings of toilets.


Lots More Information

Related Articles

  • Chiras, Dan. "Best Options for High-Efficiency Toilets." Mother Earth News, April/May 2010. (July 8, 2012) http://www.motherearthnews.com/green-homes/best-options-for-high-efficiency-toilets.aspx
  • Nash, Jenny. "The Lowdown on Low-Flow Toilets." HGTV.com. (July 8, 2012) http://www.hgtv.com/decorating/the-lowdown-on-low-flow-toilets/index.html
  • Thomas, Justin. "The Best Low-Flow Toilets." Treehugger, Aug. 29, 2005. (July 5, 2012) http://www.treehugger.com/bathroom-design/the-best-low-flow-toilets.html