How much money can you save replacing an old high-flow toilet with modern low-flow toilets? My house is old enough that we still have toilets that use about 13 liters per flush 1 instead of the modern standard of 6 liters or less. (I bet some readers landed here hoping to catch me using “literally” incorrectly. Maybe they have caught me. I’m literally flushing away something I have to pay for (water), but I’m not literally flushing coins or bills. It’s an important debate to have while I’m somewhere else.) New dual-flush toilets use either 6 liters or 3.8 liters per flush depending on whether it is a big or small flush. This makes the water savings either 7 liters or 9.2 liters per flush. In my limited experience, low-flow toilets need more second flushes than my old toilets require. Combining this with the fact that small flushes are more frequent, I’ll call the savings an average of 8 liters per flush. For my 4-person family, I estimate that we flush about 20 times per...