Can I withhold rent for every day that I do not have water?

Under New Hampshire law, a tenant is permitted to withhold rent in certain circumstances and still be protected from eviction for nonpayment. The reasons for which you are withholding your rent must be serious defects or substantial code violations which threaten the healthy or safety of the tenants who reside in the apartment; AND You give your landlord written notice of the defects at a time when your rent is current.  AND The landlord fails to correct the defects within 14 days of receiving the written notice of the defects. AND You, your family, or your guests did not cause the problem; AND Extreme weather conditions did not prevent the landlord from making the repairs. AND You did not prevent repairs by refusing to let the landlord into the unit.

Unfortunately under the laws of all states in this country you cannot legally withhold rent for every day you do not have water at your rental. The best way to resolve the issue of no water if the landlord is simply not using best efforts to get you such is to contact your local health department and ask fo an inspection of the rental. If such happens and the landlord is cited then you get the problem resolved immediately.