Water conservation wise, how long can you let the yellow mellow?

“If it’s yellow, let it mellow. If it’s brown, flush it down.”

Fine. But how long can you let the yellow mellow?

I’m the only one that uses my toilet. Of a morning I might have 3–5 yellows by the time I’m up, showered and dressed.

Traditionally, I don’t brown more than once a day, and that’s not always in the morning and not always at home.

I’m guessing that we’re not advocating leaving the toilet unflushed for 24 – 48 hours or more? It is going to be really, really rank, and eventually lead to some intense scrubbing.

So, what’s the guideline? The cutoff?
“If it’s yellow, let it mellow [until]...”