There is no starker reminder of the inability of Palestinians and Israelis to live together than the recent revelation by the Israeli human rights group B’Tselem that both sides cannot even agree to purify their regional sources of drinking water. Without such a joint effort, neither community can thrive in the often parched region. That’s why finding agreement on such relatively uncontroversial matters should be a barometer of future cooperation. Indeed, it is to this and similar projects that U.S. mediators must turn their focus as they seek to build the confidence of both Israelis and Palestinians as to the fruits of dialogue.

In short, nearly 2 million of the 2.8 million Jews and Arabs living in Jerusalem and the West Bank is not being treated. The failure to act could result in “permanent contamination” of the region’s mountain aquifer, a main water source for both Jewish and Palestinian communities. In addition, only 81 of the 121 West Bank Jewish settlements are connected to a wastewater treatment plant. Worse, many of those operations are outdated and cannot handle the full load, according to B’Tselem.

For their part, the Palestinians suffer a double blow: The waste from the Jewish communities, mostly built on hilltops, flows down to them and into their springs and wells. Meanwhile, an astonishing 95 percent of Palestinian wastewater is not treated. Not only that, but the Palestinians reportedly have refused attempts by Israel to jointly deal with wastewater. The fear, according to the Palestinians, is this would legitimize the settlements.

Regardless of what does or does not happen in the peace negotiating arena, Israelis and Palestinians need to learn how to become drinking buddies.