Hot water pipes are painted black why?

Answer: To absorb more heat.

Explanation:Dark colors absorb more heat than light colors, therefore if you spray painted black on a waterpipe the only reason could be to have it absorb more heat, the reason it needs to absorb more heat is is undentified.

Answer: Absorb heat

Explanation:

Hot water are painted black so as to absorb more heat and since black surfaces have low emission levels (emissivity), pipes painted black would retain hot water longer than normal pipes.

In essence, hot water pipes are painted black because of it's high absorption (good absorber of heat) and low emission of heat. Hence it prevents lose of heat within the pipes much better than regular pipes.