The successful use of polymer components in solar hot water systems requires an understanding and method of predicting the degradation of the material in the operating environment. In the present work, the degradation of polymer tubes exposed to potable water is studied. The relevant degradation mechanism is oxidation. Degradation from oxidation can be delayed through the use of antioxidant additives. However, once the antioxidants have been depleted, the oxidation of the polymer and subsequent loss of mechanical integrity occur rapidly. A model of the rate of antioxidant loss is developed for polyolefins. A parametric study of the effect of tube geometry is presented.