Each Rinnai tankless water heater is manufactured to be so rock-solid reliable, you can safely stake your reputation on it. And the new C199 commercial condensing tankless water heater is no exception. The robust C199 models come standard on the tankless rack system (wall mount or Freestanding) as well as individual units. Available in natural gas or Propane, the C199 is a dedicated commercial tankless model, precision engineered to produce an endless supply of hot water for even the most demanding applications—from restaurants to hotels to multifamily residences to schools and more. When the demands are greatest, Rinnai delivers.