Low-Flow Toilets: How to Choose

Replacing an old water-guzzler with a new low-flow toilet can shave as much as $90 off your annual utility bill and send thousands fewer gallons of water down the drain.

A lot has changed since 1994, when low-flow toilets became the law of the land. Early versions created a bit of a stink, because while they were good at saving water — using only 1.6 gallons per flush versus as many as 7 gallons — they weren’t necessarily good at doing a toilet’s main job.

Today’s low-flow models don’t have those problems. Not only are they much better performers, some also use even less water than the federal standard. So if you’re in the market for a new throne, it pays to consider a high-efficiency toilet (HET). You’ll save a bundle: According to the EPA, replacing pre-1994 guzzlers with new HETs will shave more than $90 off your annual utility bills. Plus, you’ll be sending thousands fewer gallons a year down the drain.

Look for high performers

The EPA’s WaterSense label on the box identifies HETs that have been certified by independent laboratories. They’re rated according to Maximum Performance (MaP) testing protocols, which measure the toilets’ ability to remove waste. MaP scores range from 250 to 1,000, based on the number of grams completely evacuated in a single flush. The EPA has adopted 350 grams as its minimum performance threshold, and “anything over 500 is very good,” says Terry Love, a plumber in Washington state who conducts his own thorough testing of low-flow toilets.

Choose a flush mechanism

Like standard low-flow toilets, HETs come with different flush options. The one you choose depends on how “green” you want to be, how much you’re willing to spend, and your tolerance for noise. Most residential toilets in the U.S. are gravity-flush, which, as the term implies, relies on the weight of water flowing into the bowl to help remove waste. Pressure-assist toilets compress air at the top of the tank to increase flush velocity, so they can do the job with as little as 0.8 gallons of water. While this turbocharged action makes for a powerful flush, the loud whoosh! may cause small children to jump out of their socks. (Somewhat counterintuitively, these also require good household water pressure to work properly.)

Some low-flow designs, like the minimalist Kohler Hatbox — so streamlined that it doesn’t even have a tank — flush with the aid of an electric pump. While that delivers a powerful flush without the noise, unlike a standard toilet it requires electricity, which can make for more complicated installation and costlier maintenance.

Calculate your savings

Toilets account for about 27%  of a household’s indoor water usage, so trading up to a high-efficiency toilet can yield big savings. According to the EPA, a family of four that replaces its home’s older toilets with WaterSense-labeled models will, on average, save more than $90 per year in reduced water bills and $2,000 over the lifetime of the toilets. You can pocket even more by taking advantage of rebates and vouchers offered by many states and municipalities. The city of Austin, Texas, for example, gives residents up to three HETs for free, though there is a modest fee for certain design features, such as an elongated bowl or a seat that meets the ADA-required height of 17 inches.

And, of course, you’ll be saving a lot of water. Pre-1994 toilets send between 3.5 and 7 gallons down the drain with every flush. For a family of four, that adds up to about 76 gallons a day. And if the toilet leaks — that is, if it continues to run after you’ve flushed or sometimes trickles mysteriously on its own — it could be chugging up to 200 extra gallons daily.

To maximize water savings, consider a dual-flush HET. The tank has two buttons that let you choose between a half flush and a full flush, depending on whether liquid or solid waste needs to go down. Caroma, a brand made in Australia (where dual-flush is mandatory), started selling these in the U.S. about a decade ago and offers nearly a dozen dual-flush lines.

Do some comparison shopping

The good news is that all this efficiency comes at a reasonable price — about $200 on average, no more than a conventional low-flow toilet. Keep in mind that price doesn’t always guarantee quality or correlate to MaP score. Before you make a purchase, check consumer reviews for specific models, noting track records for maintenance and common gripes that crop up about specific brands. Once you find a model you like, it’s easy to compare prices at Web sites such as pricegrabber.com, shopzilla.com, and nextag.com (be sure to factor in shipping and return policies). Certain features, such as elongated bowls and high-tech finishes like Toto’s SanaGloss, might add 20% to the price, but considering how long it will be until you buy your next toilet, that extra bit of ease and comfort is quickly amortized.