Here are some examples of how you could use pronouns to replace "custodian" in a sentence:
* "The custodian is cleaning the floors." -> "They are cleaning the floors."
* "The custodian mopped the hallway." -> "He/She mopped the hallway."
To use a pronoun, you need to know the gender of the custodian (if applicable). If you don't know the gender, you can use the pronoun "they" which is considered gender-neutral.