Dilution rates water to feed may affect the apparent total-tract digestibility (ATTD) of barley-wheat diets fed to growing-finishing pigs. The experiment lasted 52 d and it was divided in 2 studies of 26 d each. In the first study 16 female pigs (46.7 ± 1.98 kg of body weight, BW) were individually allotted and assigned to 1 of 4 treatments (n = 4). Treatments consisted in 4 water-to-feed ratios: in dry form (CON), with no added water, and ratios of 0.6:1, 2.1:1 and 2.7:1. In the second study the same animals (65.4 ± 3.14 Kg of BW) were again assigned to 4 new treatments: CON and 1.35:1, 2.7:1 and 3.5:1 ratios. Each pen was provided with a free-choice nipple drinker. Diet was fed close to “ad libitum” trying to avoid refusals, a 0.3% of TiO₂ was added to the feed as an indigestible marker and fecal grab samples were collected from the rectum twice a day the 2 last days of each study. Data of ATTD of OM, GE and nutrients were analyzed by one-way ANOVA using the GLM procedure of SAS and differences among mean values were assessed by the Tukey t-test. In the first study, pigs fed diets with ratios 2.1:1 and 2.7:1 had higher organic matter digestibility (OMd) and gross energy digestibility (GEd) than CON (P < 0.05). Pigs fed diets with a ratio of dilution 2.7:1 also had higher (P < 0.05) intake of digestible organic matter (DOMi) and digestible energy (DEi) than pigs fed CON. In the second study, pigs fed water diluted diets (the 3 ratios) had better OMd and GEd than CON (P < 0.05) but no differences were found in DOMi. Compared with CON, the dilution of 3.5:1 also showed a higher (P < 0.05) digestibility coefficients for crude protein (CP), ether extract (EE) and crude fiber (CF) and the dilution 1.35:1 and 2.7:1 also for CF. Using a quadratic regressions approach, the maximum feed OM and GE digestibility coefficient was found with dilution rates of 1.83:1 and 2.70:1 for the first and second study, respectively. In conclusion, the water-to-feed ratio which optimized OM and GE digestibility varies depending on the age of the animals; being lower ratios better for young pigs and higher for finishing pigs. Despite the fact that dilution rates below 2.5–2.7:1 are not usually achieved in liquid feeding commercial farms.