Reference for Moed Katan 7:11
אמר ר' אילעא א"ר יוחנן גזירה מי גשמים אטו מי קילון רב אשי אמר מי גשמים גופייהו לידי מי קילון אתו
It is quite correct [to prohibit water] from a swipe-well, because that is a rather extra trouble; but rain water-what trouble is there [in using it]? - Said R'Ela, reporting R'Johanan: Rain water is prohibited as a precaution on account of the swipe-well.<span class="x" onmousemove="('comment',' If stored rain water is permitted, one will also work a shadoof.');"><sup>12</sup></span> R'Ashi said: Rain water itself may [sometimes] come to be [just as difficult to draw<span class="x" onmousemove="('comment',' When much of it has been drawn off he will have to go deep down with his bucket, with almost as much exertion as from a shadoof.');"><sup>13</sup></span>