Afaik, most people don’t use running water anymore. try this:
https://whyfilmphotography.wordpress.com/2019/01/29/the-ilford-wash-method/
regards,
Frank
This.
I have processed film (dilute developer, reused stop and fixer, wash after fixing) with as little as
one gallon of water for two 120 rolls (loaded onto a single reel in a Paterson type tank). I know the quantity with some precision, because I was pouring from a jug of "drinking water" purchased at the local supermarket.
In the unlikely event the link above rots, the "Ilford wash" for film is pretty simple and quick: after pouring out the fixer (and shaking a tank a couple times to minimize carry over), fill the tank with tap or filtered water, and invert five times; pour out (down the drain is fine, most places). Fill the tank, and invert ten times; pour out. Fill the tank a third time, and invert twenty times. Pour out. Refill the tank for wetting agent if you use it (you should; used correctly it eliminates the need to squeegee the film, hence reducing risk of scratches).
Ilford has also espoused a similar water-saving regimen for prints, as long as they're on RC paper: fix in rapid fixer only, for no longer than (thirty seconds? one minute?), then wash for just five minutes with water changes every minute. This will use five trays full of water; for 8x10 that's less than a gallon (per print or small group of prints).