I'm no engineer, but am always thinking about practical conservation ideas with enough inherent profit motive to create a win-win scenario, where the inventor/producer and the public both benefit.

While not my first idea in the plumbing fixture realm, I think this one could actually get done and be fielded quickly, providing savings of water and money.

Problem: Water levels in toilets today assume a "worst-case" preparation, ready to swiftly take away solid mass. But how many flushes per day, across the western world, consume twice the water than needed, when it's only liquid that needs carrying away?

Solution: provide two water levels. Higher level would be the one we all know now; the new second level would be lower, default level.

Toilet, when flushed, would fill to a lower-than-usual level, adequate for those many quick visits we all pay during the day. When we need to sit a spell, for those longer visits, we'd push a button that would mechanically fill the bowl and the tank to a higher level, providing the necessary coverage and flushing power. Once flushed, water is filled to the lower default level again.

Perhaps I'm naive, but my gut tells me that the button and filling aparatus would be a small engineering project versus a new fixture design with complex moving or electronic parts and/or a new casting. My solution could also - maybe - be a retrofit for existing setups.

One weakness I see is that children or the elderly may not select the higher level when needed, causing backups. Perhaps this new design should have the option to override the default, keeping it at the higher level. Hmmmm... What else am I not addressing here?