Does Sunlight (UV) affect PVC pipe and fittings?
PVC Fittings and Pipes are generally subterranean Irrigation Supplies (they are generally used below ground). On occasion however, these Landscape supplies will be laid above ground. In these cases it is important to know of the adverse affect sunlight (UV) can have on PVC pipe and fittings.
PVC pipes and PVC fittings exposed to sunlight for periods of two years or longer will experience decreases in impact strength and resistance. This is not a major problem when dealing with PVC pipes and fittings as impact strength and resistance are not qualities generally associated with PVC. PVC Pipe and Fitting exposure to UV sunlight for periods of two years or less will not have any effect on the PVC's stiffness, pressure capacity, strength, or modulus. For periods longer then two years however, there can be minimal effects to these qualities. Generally, the thinner the pipe, the more the UV rays will affect the pipe's strength or flexibility.
Indications of UV exposure on the PVC Pipe or PVC Fitting will begin with a slight discoloration to the Landscape supply in question. Discoloration to the fitting or pipe will begin pretty quickly if the PVC fitting or Pipe is laid above ground. You will not need to worry about negative effects upon the flexibility or strength until after two years (as I stated before), but there are simple ways to prevent both the discoloration and the long-term negative effects upon the PVC.
Your first option is to use UV resistant Fittings (PVC UVR Fittings). UV resistant fittings are PVC fittings with a titanium dioxide additive that gives the PVC a beige tint. The pigment will reduce the UV light discoloration of the PVC polymers. The second option is to either paint or coat the PVC Pipe or Fitting. Covering the PVC will prevent negative effects from UV light. Just be sure that when you cover the PVC (if it is for storage purposes) you allow ventilation as the heat can do more damage to the PVC than the UV light you were trying to protect it from.