The problem is that the US Armed Forces are required by law to meet US civilian water purity standards. There are plenty of portable devices or methods out there that produce adequately safe drinking water -- not least Chlorine or Iodine tablet; Aquamira Tablets, among others, are better than either. The problem is that the tablets and most of the devices or filters don't meet the EPA standard. That standard is massive overkill but the bureaucracy will have its way...

For current bulk water production this is used (LINK .pdf) and it is to be replaced by this (LINK) with increased capability and it mounts in / on a HMMWV instead of a HMTT or Mk28 MTVR. The Army has a large number of Water Purification and Distribution units and was prepared for a major war and making much pure water. They were not prepared for a small war and making a little bit of pure water.

There are several smaller variants, including a number of Kärcher units and SOCOM in particular buys and uses outpost sized units. For regular Army Co / Plat size patrols, units buy these (LINK) with own funds. They don't advertise that they have and use them due to the extremely stringent US EPA Water Safety standards. This new item (LINK .pdf) apparently meets the standards and is to be bought on a major contract. Note that it already has a NSN and a GSA contract.

I would make a comment about just ignoring civilian rules in combat zone but that might be considered subversion so I will not do that. Sigh...