There are three main types of chimney liners. These include clay tile liners, cast-in-place liners, and metal liners. All three types provide adequate protection but which liner is appropriate for your home, should be determined by a professional.
Often when having a new natural gas or propane water heater installed, a new chimney liner is recommended, or even mandated by code. This requirement is a critical safety consideration for your property and addresses several issues.
Information provided by Lindemann Chimney and Fireplace 2018