Legal Question in Landlord & Tenant Law in Texas

Under Texas law, the landlord owes the tenant the duty to keep and maintain the property in a safe and habitable condition. The laandlord is also responsible for making all major repairs to the property. Furthermore, housing codes that require every landlord to provide "the basics": hot & cold running water, a roof that doesn't leak, safe wiring, etc. The landlord must provide habitable premises when you move in and make repairs to these basics as they are needed.

They may be in violation of the lease, read it carefully. Read also the Texas implied warranty of habitability but becareful on such actions like a rent strike. You may call the city to make sure the landlord is following "local housing codes" when in this case they are not providing hot water.