On Tue, 20 Apr 2010 00:00:31 +0000 (UTC), Brent wrote:

What's the difference from a practical standpoint for
outdoor 12-hours-a-day-in-the-sun 2-inch OD pool water pipes
between black ABS and white-painted-black PVC pipe?

"The Effects of Ultraviolet Radiation on PVC Pipe"
http://www.uni-bell.org/pubs/uni-tr-5.pdf

Summarized by the PVC Pipe Association he
http://www.uni-bell.org/faq.html

Further summarized by yours truly below:
Q: What effect does ultraviolet exposure have on PVC pipe?
A: Not much but enough to warrant a thin coat of opaque paint!

Modulus of Elasticity = unchanged after two years of sun
Tensile Strength = unchanged after two years of sun
Impact Strength = reduced drastically (by 75%) after two years of sun
Structural Integrity = unchanged after two years of sun
Pressure Capacity unchanged after two years of sun

The loss of impact strength stopped deteriorating as soon as the pipes were
protected by the sun so it's directly related to the UV radiation.

Luckily, the presence of an opaque surface between the sun and the pipe
prevents UV degradation, since UV radiation will not penetrate thin shields
such as paint coatings or wrappings or burial.

Why black? What's more opaque than black? Electrical PVC outdoor pipe is
gray. Go figure.

PS: I heard some paint won't stick to PVC so maybe you need special PVC
paint?