A peritoneal dialysis system configured to perform a method comprising: flowing dialysate along a first flow path through a manifold and into a dialysate reservoir, the manifold comprising a manifold body that defines a plurality of internal passageways and a plurality of ports providing fluid communication to fluid passageways external to the manifold body, the plurality of internal passageways comprising the first flow path, a second flow path, a third flow path, and a fourth flow path; weighing the dialysate in the dialysate reservoir to obtain a first weight; flowing the dialysate out of the reservoir, along a second flow path through the manifold, and into a peritoneal cavity; flowing the dialysate out of the peritoneal cavity, along a third flow path through the manifold, and into a drain reservoir; weighing the dialysate in the drain reservoir to obtain a second weight; and flowing the dialysate out of the drain reservoir and along a the fourth flow path through the manifold, the system comprising: the manifold; a dialysis machine in operable communication with the manifold and configured to flow the dialysate through the first, second, third, and fourth flow paths; the dialysate reservoir in fluid communication with the manifold; the drain reservoir in fluid communication with the manifold; a scale configured to weigh at least one of the dialysate reservoir and the drain reservoir; and a heater configured to heat dialysate in the dialysate reservoir. flowing dialysate along a first flow path through a manifold and into a dialysate reservoir, the manifold comprising a manifold body that defines a plurality of internal passageways and a plurality of ports providing fluid communication to fluid passageways external to the manifold body, the plurality of internal passageways comprising the first flow path, a second flow path, a third flow path, and a fourth flow path; weighing the dialysate in the dialysate reservoir to obtain a first weight; flowing the dialysate out of the reservoir, along a second flow path through the manifold, and into a peritoneal cavity; flowing the dialysate out of the peritoneal cavity, along a third flow path through the manifold, and into a drain reservoir; weighing the dialysate in the drain reservoir to obtain a second weight; and flowing the dialysate out of the drain reservoir and along a the fourth flow path through the manifold, the system comprising: the manifold; a dialysis machine in operable communication with the manifold and configured to flow the dialysate through the first, second, third, and fourth flow paths; the dialysate reservoir in fluid communication with the manifold; the drain reservoir in fluid communication with the manifold; a scale configured to weigh at least one of the dialysate reservoir and the drain reservoir; and a heater configured to heat dialysate in the dialysate reservoir. the manifold; a dialysis machine in operable communication with the manifold and configured to flow the dialysate through the first, second, third, and fourth flow paths; the dialysate reservoir in fluid communication with the manifold; the drain reservoir in fluid communication with the manifold; a scale configured to weigh at least one of the dialysate reservoir and the drain reservoir; and a heater configured to heat dialysate in the dialysate reservoir.