Legal Question in Real Estate Law in California

You can, at most twice a year, withhold up to a month's rent to hire a contractor to fix a so-called "dilapidation," meaning things that make the rental property untenantable, such as no water. However, you have to give the landlord advance notice of the problem and a reasonable opportunity to make repairs. Further, you can't just withhold the money, you have to spend it to do the repair, and you'd better get receipts to prove how much you had to spend.

Since you didn't really say what the problem is, I can't say whether it amounts to a dilapidation or what relation the "water part" of what you owe the landlord has to do with the cost to fix the problem, if anything.