Mikvaos 6:2-3

Mikvaos 6:2

If a bucket full of utensils is immersed, they’re purified; if the bucket isn’t immersed, the water in it isn’t considered joined with the mikvah unless it’s joined by a hole the size of a waterskin’s spout.

Mikvaos 6:3

Let’s say that there are three mikvahs, two of which have 20 seah of valid water in them and one of which has 20 seah of drawn water, and the one with drawn water is on the side. If three people immerse in these mikvahs and their waters combine, then all three mikvahs are valid and those who immersed are purified. If the mikvah with the drawn water is in the middle and three people immersed in them and the waters combine, the mikvahs maintain their status quo and those who immersed maintain their status quo.