Since it was in the lease agreement, the Judge is likely to believe that you knew about the water bill and the landlord will argue you aren't released from your obligation. However, under the doctrine of laches,
"In California, a plaintiff who has unduly delayed seeking equitable relief to the prejudice of a defendant may be barred by the doctrine of laches. (Concerned Citizens of Palm Desert v. Bd. of Supervisors (1974) 38 Cal. App. 3d 257, 265-266.) In that case, the court found that there was substantial evidence of unreasonable delay plus prejudice supporting the trial court decision to sustain the defense of laches.
Laches is ordinarily a question of fact, and therefore, the trial court can exercise considerable discretion in deciding whether the defense should be sustained."
that was from Frank Chen's post of several months ago. So one may argue that you are prejudiced by the failure of the landlord to forward the bills to you and should not be hit with the $1500 because of his failure to forward the bill. I would caution you against allowing an eviction lawsuit to be filed against you on this basis because it can make it difficult to rent elsewhere, so think carefully how to proceed and seek local legal counsel for advice. I can only provide legal information here, not legal advice.
The landlord may have a legal claim to seek payment of the water bill by you because of the terms in the lease agreement. However, as the previous attorney stated, you may have an equitable defense to the landlord's claim known as Laches.
Simply stated, laches is the principle whereby the defendant would be unfairly prejudiced by the Plaintiff's delay in properly bringing his/her claim.
Prejudice may be shown by the defendant's change in position, suffering of certain consequences, or otherwise taking actions he/she would not have had the plaintiff properly brought suit without delay.
This response does not create an attorney-client relationship between you and I. I am not your lawyer and I am not representing you in the underlying issue stated in your question. The response I have offered is not intended to be relied upon, you should seek out an attorney to assist in this matter.