My landlord has back-billed me for 4.5 years of water utilities and are saying I owe them money. The lease does state that the tenant pays for water (split as a percentage with the adjacent duplex unit), however, it also explicitly states that this utility would be billed to the tenants every two months. We have never received a single bill from them regarding this utility, nor have we received any notification of violating our lease. They have failed to bill us and are charging it as a lump sum. I asked them why they never billed us, when they did send the percentage bill to the adjacent unit, and all they said was theyre "not sure" and may have "overlooked it". They are desperate to get me to move out since it is a rent-controlled unit and I feel like they have done this to cause issues and force me to default on rent. Is this a legal practice? Does the "billing every two months" in the lease have any hold on this issue if they breached their own lease? We honestly forgot about this utility on our end because our other utilities are on autopay, and without receiving any bills, it was out of sight out of mind. Is there anything we can do?
Can landlord backbill 4.5 years worth of utilities that were never billed to us bimonthly as directed in the lease?
Yes, since the bimonthly billing issue appears to be within the LA statute of limitations for claims of breach of contract: 10 years (see here). But you might want to check the actual legislative language of the statute referred therein and the prior or consecutive ones --all pertaining to statutes of limitations-- so as to ascertain the accuracy of information in the first link (navigating through the bunch of LA two- or three-line statutes for this and that gets annoying).
They are desperate to get me to move out since it is a rent-controlled unit and I feel like they have done this to cause issues and force me to default on rent. Is this a legal practice?
I am not knowledgeable of state legislation particular to rent-controlled units, but I highly doubt it is lawful for them to proceed that way. Other details you describe reflect that the company has been --or is being-- malicious or grossly negligent. If so, strictly speaking, the company's conduct (1) ought to weaken its position or merits in trying to force you out, and (2) tends to contravene the contract law covenant of good faith and fair dealing (see below).
If your lease mentions any statutes regarding rent-controlled units, you may want to search for case law at leagle.com to see how the statutes are applied.
Without knowing the terms of your lease, I think your priority should at all times be the rent itself so as to avoid eviction.
Does the "billing every two months" in the lease have any hold on this issue if they breached their own lease?
Maybe not. The repeated, yet sole, failure to send you the bimonthly billings falls short of landlord's breach of contract.
For your argument on breach of contract to prevail, you would have to prove that the landlord knowingly/deliberately let the water bills pile up prior to demanding you to pay everything at once. That would prove that the landlord is not meeting the covenant of good faith and fair dealing that is prerequisite in contract law.
Firstly, you did originally agree to pay them this money, so you have a moral obligation to pay at least some of it.
Secondly, there is limitation on how far back one can sue for money under a contract. If California, for breach of a written contract, it is four years, so you probably don't owe the first six months of the bill.
Thirdly, this money is not rent. Thus failing to pay it probably isn't a reason to evict you. (Consult your own paid-for lawyer to confirm that.) Edit Check your lease: the lease may make failure to pay such bills grounds for eviction.
Fourthly, there is a principle in some common law jurisdictions that if one party makes a mistake (not sending the bill), and the other party erroneously relies on that (by spending the money on something else), then the first party cannot later sue for the money. So if you have been piling up savings, then you have to pay; but if you have essentially nothing, then you don't. I don't know if this applies to California or not (I can't find the term to search for.) Edit A comment below strongly suggests this may not apply: Ohwilleke is rather more knowledgeable than me about law in American jurisdictions.
Given that this is a rent controlled property, it would probably be quite expensive to move somewhere else. As such, I suggest you write to them saying this is their error, and you have been (by mistake) relying on their error and have spent the money. As such, they should forgive one third of the debt (particularly as they cannot sue for the first six months anyway); and you will pay the remainder over the following two years (plus your rent and the future itemized bills as they become due).
Finally, given that this has the potential to cost you the roof over your head, I strongly suggest that you pay for at least a 30 minute consultation with your own lawyer.