You can get dirty water in Fallout 4 either by buying it, looting it, or (in Survival difficulty) actually filling bottles at dirty water sources.

Basic ways to get Dirty Water

  • Loot it from containers, coolers, and random world stashes, especially around urban areas and raider hideouts.
  • Buy it from vendors; for example, Scarlet at the Dugout Inn in Diamond City often sells a few bottles each refresh.
  • Steal a small stash of dirty water bottles from the counter near the noodle vendor in Diamond City if you are okay with theft.

Survival mode bottle filling

In Survival difficulty, there is an extra mechanic that makes dirty water much easier to farm.

  • Make sure you have empty bottles in your inventory (beer, Nuka-Cola, etc.).
  • Go to a dirty water source like a river, pond, or irradiated pool and activate it while on Survival; the game converts the empty bottle into a Dirty Water item.
  • If you instead use a settlement water pump while in Survival, the bottle fills as Purified Water, not dirty.

One-time “Survivor switch” trick

Some players use a small workaround to mass‑farm dirty water on non‑Survival playthroughs.

  • Temporarily switch your difficulty to Survival.
  • Step into a dirty water source and use the prompt to “grab Dirty Water” while you have empty bottles.
  • After filling as many as you want, change difficulty back; note that reports say this particular trick only works once per playthrough, so bring lots of bottles.

Extra tips for farming

  • Save all empty bottles you find; if you plan to cook a lot of soups (like veggie soup), dirty water becomes the bottleneck.
  • Check places rich in bottles such as breweries, cafĂŠs, schools, and Red Rocket stations so you can stock up before a filling run.
  • If vendor stocks feel too slow, combine Scarlet’s inventory with other general traders and rotate between them, waiting 48–72 in‑game hours for refreshes.

Quick HTML table of methods

html

<table>
  <thead>
    <tr>
      <th>Method</th>
      <th>Where/How</th>
      <th>Notes</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Looting</td>
      <td>Containers, coolers, world loot in cities and raider zones [web:5]</td>
      <td>Unreliable but free; pick up every bottle you see.</td>
    </tr>
    <tr>
      <td>Buying</td>
      <td>Vendors like Scarlet at Dugout Inn in Diamond City [web:5]</td>
      <td>Wait 72 hours to restock, then buy again.</td>
    </tr>
    <tr>
      <td>Stealing</td>
      <td>Counter by the noodle vendor in Diamond City, small stash [web:5]</td>
      <td>Counts as theft; watch for guards.</td>
    </tr>
    <tr>
      <td>Survival filling</td>
      <td>Use empty bottles at dirty water sources while in Survival difficulty [web:3][web:5]</td>
      <td>Most reliable long‑term farm if you play Survival.</td>
    </tr>
    <tr>
      <td>Difficulty swap trick</td>
      <td>Temporarily switch to Survival, fill bottles, then switch back [web:1]</td>
      <td>Reported to work only once per playthrough, so bring many bottles.</td>
    </tr>
  </tbody>
</table>

Information gathered from public forums or data available on the internet and portrayed here.