Replace your old toilet with a high efficiency toilet.
High efficiency toilets save approximately 1/3 of a gallon of water per flush compared to standard toilets and save 2 to 4 gallons compared to pre-1994 models. Most of these toilets meet the high reliability standards required to be certified as Water Sense toilets. That means they are efficient and flush well every time. Make sure you select Water Sense certified toilet when you make the switch.
One of my favorite brands is TOTO. They have a variety of toilets that have earned the Water Sense certification and are available in contemporary styles. If you are more traditional, there are options for you as well. For instance, this American Standard model also uses a high efficiency flush and receives excellent customer reviews.
There are a couple of other options for the more adventurous of you out there. The first one is a dual flush toilet model. Dual flush models provide two different volumes of flush to be determined by the user, either 1 gallon or 1.6 gallon flushes. That ends up about 0.3 gallons higher or lower than the standard 1.28 gallon high efficiency toilets discussed above. Most people decide it is not worth the hassle for something that will likely average out to the 1.28 gallons anyway. Plus, there is the potential confusion that a two-button option could cause guests. I for one am willing to throw caution to the wind and let my guests keep pushing buttons until something happens! If you are with me, these are some good options to check out. EGAO’s sleek one piece and American Standard’s H2Option Siphonic.
The least desirable option for decreasing water usage at the toilet is a retrofit kit.
Some of these do work, but the results will be sub par compared to a new dual-flush or single-flush high efficiency toilet. High efficiency toilets have larger diameter internal cast ceramic piping and shorter goose necks allowing for quicker evacuation of solids and liquids than older toilets allow. So, if you retrofit an old toilet with a new plunger and handle system, you still have your old toilet’s piping. There is no way around that with a kit. That means that the best retrofit systems only adjust the flush meant for liquids. If your toilet is pre-1994, you could still be flushing away very large amounts of water on half your flushes (flushes for solids) since old toilets typically used 3.4 gallons per flush instead of the maximum 1.6 gallon flush volume required today. Having said that, lots of people end up quite happy with good retro fit kits like this, and they are much happier paying $30 instead of a few hundred to replace a toilet. Both replacing a toilet and installing a retrofit kit are possible for a handy DIYer, so, one way or the other, take the plunge and start using less water!