The aim of this study was to evaluate the effects of a nutritional program with reduced crude protein (CP) content on water use and manure production. Forty gilts and 40 barrows (24.5±1.8 kg) were distributed in a randomized block design with two treatments, 10 replications per treatment and four animals per experimental unit. The feeding program was in four phases. Two diets were formulated for each feeding phase. The first one was adjusted by using InraPorc® model (LP) to adjust nutrient supplies to animal’s requirements, and the second was formulated according to standard Brazilian nutritional levels (SP). Water was supplied ad libitum and consumption was measured by using a water meter for each pen. The volume of the manure was calculated for every pen by measuring its height in the collector rails with a graduated ruler. The average protein content was 145 and 168 g/kg for LP and SP treatments, respectively. Nutritional adjustment allowed a reduction of protein intake by 13, 20, 14 and 15% in grower I, grower II, finisher I, and finisher II phases, respectively. There was no effect of treatments on water use (6.17 and 5.84 l/d for LP and SP respectively, P=0.78), and volume of manure produced (4.05 and 3.70 l/d for LP and SP respectively, P=0.61). It is reported in literature that, for each percentage point of reduction in CP, water intake is reduced by 2% and slurry volume is reduced by 4%. However, this effect was not observed in this trial, probably because the difference in protein content was not enough to influence water intake. Another reason could be the high ambient temperature (average 22 °C) which is also known to affect water consumption. The results of this trial indicate that water use and volume of manure produced by growing-finishing pigs are not affected in the range of protein levels evaluated in this study, at hight temperature.