C. Charles Hahn said:
Before deciding to offer or not offer a warranty, be sure to read through all of the obligations and responsibilities you as the installer would incur. While I have not yet seen the paperwork and information in its entirety, it is my understanding that part of the cost of performing warranty repairs falls on the installer (namely the cost of correction chemicals and labor). In those instances you may want to consult your CPA to determine how those items would be expensed out as well as whether you need to carry and track a "pre-paid warranty" asset account on your balance sheet as a means to write off potential repair concerns.
The administrative complexities may or may not be worthwhile depending on your business model and/or your comfort level in dealing with all of the implications involved, even if the chances are a claim wouldn't be filed often (if ever).