The Last Caretaker Water Guide: Water Pump, Purifier and Dehumidifier

Fresh water takes three machines: a Water Pump draws salt water from the sea, a Water Purifier turns it into fresh water, and the fresh water goes into a Water Tank or straight to the machine that uses it.

You can’t build a Water Pump. Use the one at the stern of your boat or the pumps already installed at the Lazarus Complex.

Run a hose from the pump’s salt-water outlet into the purifier’s lower salt-water inlet; the fresh water comes out of the purifier’s upper outlet. Hover over a port to see which one it is, and click a hose connection to change the way it flows.

The Water Purifier is a skill-tree unlock at Tier 7. It takes 2 Alloy Frames, 1 Compression Pump, 3 Connector Ports and 1 Filtering System, and draws 8 kW while it runs.

No. A Water Tank holds fresh water only and salt water can’t be stored, so a tank hosed straight to the pump stays empty: put a Water Purifier between them.

A Water Tank unlocks at Tier 11 and takes 2 Alloy Frames, 2 Connector Ports, 1 Filtering System and 2 Storage Cylinders.

The wiki gives the Water Tank 2,000 L.

Not confirmed yet

Every machine in the chain has its own power switch: the pump, the purifier and whatever takes the water, such as a Lazarus rack or a Food Processor. A water system with one machine switched off does nothing.

Each machine also needs a power cable and enough power behind it. Forgetting the purifier’s cable is a common reason for no water.

How much power the pump itself draws is not settled: the wiki gives 5.6 kW and says it scales, while a February 2026 player gives 10 kW.

Not confirmed yet

Channel37: a Lazarus rack also shows “No Power” when it has no working fresh-water supply. If the water is connected, save and reload, then try again, or recover a previous auto-save.

Put Water Tanks between the purifier and the Lazarus racks. They store fresh water while the purifier works, so the racks and other machines draw from the tanks instead of waiting on the purifier.

A flashing yellow light on the pump or purifier may mean the receiving tank is full, or that the water has nowhere to go; attaching a tank has fixed it.

Not confirmed yet

A hose that stops passing water can come back after you disconnect and reconnect one end.

Not confirmed yet

How many purifiers one pump can feed is not settled. The wiki’s figures (a pump giving 20,000 L and a purifier taking 10,000 L an hour) suggest two; players have reported one each, three, and up to ten.

Not confirmed yet

Put Water Tanks between the purifier and the Lazarus racks. They store fresh water while the purifier works, so the racks and other machines draw from the tanks instead of waiting on the purifier.

The rack’s Estimation screen shows 10,000 L of fresh water to grow one human. It stays the same whatever food and memory items you load; only the growth time changes. A rack holding a seed uses 100 L/h of fresh water in standby, separate from the growth water estimate.

Update 03 added the Dehumidifier.

It makes fresh water from the moisture in the air, so it needs no pump or purifier, only power. It unlocks at Tier 11.

It draws less power than a pump and purifier but makes much less water, and its output follows the weather: low on a dry day, higher when it rains.

One player measured about 800 L an hour on a dry day; another found one Dehumidifier enough for two planters.

Not confirmed yet

If it makes no water, check its power cable, press its big red button to switch it on, and make sure the tank it fills is not already full.