If you know only one thing about toilets these days, it's probably that they're required by law to limit how much water they use per flush. For many consumers, today's "low-flow" toilets are a big pain in the... you know. A toilet may use very little water, but if you have to flush it three times in a visit, its advantage is lost.

It was 10 years ago that Congress required all new toilets to flush no more than 1.6 gallons of water, less than half the previous level of 3.5 gallons. A USA Today article cites an Environmental Protection Agency estimate that as more and more low-flow toilets are placed in service, they could save nearly 8 billion gallons of water per day by 2020. (For context, consider that the soft-drink industry uses more than 12 billion gallons of water in carbonated soft drinks every year.)

Initial low-flow toilets left a lot to be desired, and many of those who installed them are only now getting around to replacing them. Toilet manufacturers have been working on win-win solutions. Take American Standard (NYSE:ASD), a leading maker of air-conditioning systems, plumbing products, and automotive braking systems. It's currently advertising its "Champion" toilet, which apparently can dispose of two dozen golf balls in a single flush. Credited for permitting this is a wider flush valve and trapway.

Other toilet innovations include a mold-reducing glaze coating and increased seat height. (Many toilets today have you perching at chair-height, which is more comfortable for the elderly, among others.) Privately held Kohler has introduced its "Ingenium" flushing system, featuring a longer period of swirling water. Its Cimarron toilet sports side jets to propel water. The Briggs Vacuity toilet, highly rated by Consumer Reports magazine, uses vacuum chambers to clear the bowl.

Some of the most ambitious toilets hail from Japan. Toto's Neorest toilet, for example, greets a visitor by lifting its lid automatically. It also boasts a seat warmer and air deodorizer -- and a price tag of several thousand dollars. Toilets of the future may do much more, such as give you a bit of a medical checkup, evaluating your output for red flags such as blood. One Toto toilet already can check sugar levels in urine, serving the diabetic market.

So, the next time you're strolling through the aisles of Home Depot (NYSE:HD), Lowe's (NYSE:LOW), or your local hardware store, spend some time in the plumbing department. New and improved toilets often command bigger bucks and generate bigger profits for retailers and manufacturers alike -- good news for investors.

If you're not interested in the Champion toilet, consider instead our new newsletter, Motley Fool Champion Funds, which delivers promising mutual funds to you each month.

Longtime Fool contributor Selena Maranjian does not own shares of any companies mentioned in this article. But she does own several toilets.