A dialysis machine includes an ultrafiltration pump that pumps fluid from a pump inlet to a pump outlet, and a calibration fluid container. The container including a bottom, an upstanding sidewall, a container inlet and a container outlet, the bottom and the upstanding sidewall defining a container interior. The container may be to the atmosphere. At least the container outlet being disposed in the sidewall proximate to the bottom. The first end of a first hose is fluidly coupled to the pump inlet, and the second end of the first hose is removably, fluidly coupleable to the container outlet. The first end of a second hose is fluidly coupled to the pump outlet, and the second end of the second hose is removably, fluidly coupleable to the container inlet. In this way, a calibration process may be performed when the second ends of the first and second hoses are fluidly coupled to the container outlet and the container inlet, respectively.