Fontan circulation involves a series of surgical operations for paediatric patients with congenital heart diseases (CHD) like hypoplastic left heart syndrome (HLHS). Despite surgery resulting in a univentricular heart structure, Fontan circulation remains palliative and can lead to complications such as heart failure and increased central venous pressure (CVP). Researchers have proposed mechanical assist devices to alleviate these complications, either a Left Ventricular Assist Device (LVAD) or Cavopulmonary Assist Device (CPAD). This preliminary study evaluates a novel balloon pump for Fontan circulation as a CPAD. The pump, connected to a vertical water column and driven by a linear actuator, made off rack and pinion mechanism, was tested at three water column heights. Statistical analysis of water displacement, battery power consumption, and sound intensity was conducted. Results showed the balloon pump prototype performed well, with an average water displacement of nearly 60 mm (4.4 mmHg of pressure) and a noise level below the NIOSH recommendation at 59.8 dB. The device, powered by a 12 V 5000 mAH battery, operated for over 4000 s. All results were within the target design range, supporting further development for potential clinical application in Fontan patients.