A peritoneal dialysis system comprising: a housing; at least one pump carried by the housing and configured to fill a patient with fresh dialysate and drain spent dialysate from the patient; and a logic implementer (112, 114, 118) configured in an ultrafiltration evaluation sequence to: (i) cause the at least one pump to pump fresh dialysate to the patient and to completely drain spent dialysate from the patient after a first dwell time; (ii) determine, as a portion of the first spent dialysate, a first amount of ultrafiltrate ("UF") removed from the patient for the first dwell time; (iii) cause the at least one pump to pump fresh dialysate to the patient and to completely drain spent dialysate from the patient after a second and different dwell time; (iv) determine, as a portion of the second spent dialysate, a second amount of UF removed from the patient for the second, different dwell time; (v) determine a third amount of UF removed from the patient over a third, different dwell time; (vi) fit a curve to the amount of UF removed from the patient for the first, second and third dwell times; and (vii) determine at least one of (a) a patient hydraulic permeability coefficient and (b) a patient fluid absorption coefficient from the curve. a housing; at least one pump carried by the housing and configured to fill a patient with fresh dialysate and drain spent dialysate from the patient; and a logic implementer (112, 114, 118) configured in an ultrafiltration evaluation sequence to: (i) cause the at least one pump to pump fresh dialysate to the patient and to completely drain spent dialysate from the patient after a first dwell time; (ii) determine, as a portion of the first spent dialysate, a first amount of ultrafiltrate ("UF") removed from the patient for the first dwell time; (iii) cause the at least one pump to pump fresh dialysate to the patient and to completely drain spent dialysate from the patient after a second and different dwell time; (iv) determine, as a portion of the second spent dialysate, a second amount of UF removed from the patient for the second, different dwell time; (v) determine a third amount of UF removed from the patient over a third, different dwell time; (vi) fit a curve to the amount of UF removed from the patient for the first, second and third dwell times; and (vii) determine at least one of (a) a patient hydraulic permeability coefficient and (b) a patient fluid absorption coefficient from the curve. (i) cause the at least one pump to pump fresh dialysate to the patient and to completely drain spent dialysate from the patient after a first dwell time; (ii) determine, as a portion of the first spent dialysate, a first amount of ultrafiltrate ("UF") removed from the patient for the first dwell time; (iii) cause the at least one pump to pump fresh dialysate to the patient and to completely drain spent dialysate from the patient after a second and different dwell time; (iv) determine, as a portion of the second spent dialysate, a second amount of UF removed from the patient for the second, different dwell time; (v) determine a third amount of UF removed from the patient over a third, different dwell time; (vi) fit a curve to the amount of UF removed from the patient for the first, second and third dwell times; and (vii) determine at least one of (a) a patient hydraulic permeability coefficient and (b) a patient fluid absorption coefficient from the curve.