Hydro Penis Pump. The Hydromax Hydropump is a hydro-therapy system that works using the natural strength of water. The hydropump can be used easily and safely in the bath or the shower. It makes impressive erections possible and can lead to a permanent enlargement of the penis. Transparent. Complete length of pump 26.5 cm ? suitable for a max. penis size of 14.5 cm (when erect). ? 5 cm. Material: PC (polycarbonate), TPE.