A landlord's failure to fix plumbing issues resulting in water that is undrinkable constitutes a breach of the rental ageement as well as violations of the California Civil Code related to tenantability of the dwelling unit. I recommend you have an attorney send a demand letter to the landlord stating that if these conditions are not repaired by X date, you will vacate the unit and sue for your damages. You should give the landlord the opportunity to repair the unit first before deeming the contract breached and vacating, but you don't have to wait forever for that to happen. Also, some conditions are so unhealthy and dangerous that it necessary for the tenant to move out right away. I do not know if that is the case for you. You can find a great tenant attorney on this website by clicking the Find a Lawyer tab. I will add that you can also make a complaint with the local housing code enforcement agency. They may red tag the building, which may cause you to have to vacate sooner than you may like to, but you can then sue for your damages.
The information provided herein is general information only and not legal advice. The information provided herein does not create an attorney client relationship and is not a substitute for having a consultation with an attorney. It is important to have a consultation with an attorney as the information provided in this forum is limited and cannot possibly cover all potential issues in a given situation.
I agree with the above that there is question as to the habitability of the premises. Keep in mind that in addition to damages for breach of the rental agreement, you could potentially be entitled to relocation fees for your moving costs. A full consultation with an attorney is always recommended for planning a tailored strategy.