May one wash floor rags on Chol Hamoed? 
Yes.<a href="#_ftn1" name="_ftnref1">[1]</a> One may do so if there are no other rags available.
<a href="#_ftnref1" name="_ftn1">[1]</a> As they become dirty constantly, and hence falls under the allowance of the Michaber in 534:1

Shulchan Aruch HaRav | Washing floor rags on Chol Hamoed

May one wash floor rags on Chol Hamoed? Yes.[1] One may do so if there are no other rags available. [1] As they become dirty constantly, and hence falls under the allowance of the Michaber in 534:1