Be cautious about:(1) who you take advice from regarding City/County laws and (2) making any alteration to rent (i.e. deductions) without first speaking with an attorney.
In many states there are valid reasons to withhold rent--HOWEVER, failing to withhold rent IAW your state's laws(there are fixed processes and procedures) can, and frequently does result in an unexpected evition for unlawful detainer against the tenant!
READ THIS BEFORE CALLING OR EMAILING ME: I am licensed to practice before the state and federal courts in Virginia. We have not established an attorney-client relationship unless we have a signed representation agreement and you have paid me. I am providing educational instruction only--not legal advice. You should speak with an attorney to whom you have provided all the facts, before you take steps that may impact your legal rights. I am not obligated to answer subsequent emails or phone calls unless you have hired me. I wish you the best of luck with your situation.
I am an attorney licensed in New York. I do not practice law in Texas.
Unless your lease or locality has a different provision, a Texas landlord who is not providing hot water of at least 120 degrees, must be informed by the tenant of the lack of adequate hot water, in the manner required by the statute, and as long as the landlord is properly notified and the tenant is paying the rent, the landlord must restore the hot water to the legal temperature.
As provide at: PROPERTY CODE -- TITLE 8. LANDLORD AND TENANT, CHAPTER 92. RESIDENTIAL TENANCIES at Chapter B:
"***Sec. 92.052. LANDLORD'S DUTY TO REPAIR OR REMEDY. (a) A landlord shall make a diligent effort to repair or remedy a condition if:
(1) the tenant specifies the condition in a notice to the person to whom or to the place where rent is normally paid;
(2) the tenant is not delinquent in the payment of rent at the time notice is given; and
(3) the condition:
(A) materially affects the physical health or safety of an ordinary tenant; or
(B) arises from the landlord's failure to provide and maintain in good operating condition a device to supply hot water of a minimum temperature of 120 degrees Fahrenheit.***"
You could check with your local code enforcement office and with a local lawyer. But it would appear from the statute that if you are not paying your rent you cannot use the statute to force the landlord to provide adequate hot water.
The answer provided to you is in the nature of general information. The general proposition being that you should try to avoid a bad outcome if you can.