Capitalism doesn't "win"; just like anarchism, it has downsides. In anarchism, as you said, nothing has market value, so priorities are nebulous. Well, the downfall of capitalism (from an ethical standpoint) is that everything has a price, including human life, labor, and injury.
Ethically, I prefer the side of the fence that grimaces at such valuation, even if things are less efficient for that side. Why? Well, because on the other side, the greatest efficiencies are only accessible to the wealthiest people: There is an "efficiency" (quality of life) gradient that is directly tied to personal wealth, and it's disgusting. We've known for a long time now that wealth does not necessarily follow virtue or hard work.
Is there something particular about sewers that prohibits them from being public works? Further, no moral society allows sewage to be solved by pure capitalism, because the obvious consequence would be to let the poor rot in their own filth. Sadly, in many parts of the world, this is the case.
A glance at the world's countless poor and downtrodden shows that global capitalism is a miserable failure, so I think it's unfair to point out theoretic deficiencies of anarchism or other systems as reason to persist with the status quo. "Don't point out the splinter in another's eye when there is a log in your own."