Fresh water can be separated from saltwater with a surprisingly simple process.

Heat turns water into vapor. The salt remains behind in the boiling pot. When the vapor passes through a cooled tube, it condenses back into liquid water that can be collected in a separate container.

That process is called distillation.

A small homemade distiller can be useful for:

Demonstrating desalination
Producing limited backup water
Treating small quantities of known saltwater
Learning how evaporation and condensation work
Producing distilled water for certain equipment
Testing an off-grid water-processing method

However, this is not a fast or universal water solution.

Distillation generally requires more energy and takes longer than many other household water-treatment methods. It can remove parasites, bacteria, viruses, dissolved salts, minerals, and many chemicals, but it does not reliably remove every volatile solvent, volatile organic compound, or pesticide. (CDC)

A homemade system should therefore supplement stored emergency water—not replace it.

CDC recommends storing at least one gallon of water per person per day for three days and advises keeping a two-week supply when possible. Commercially bottled water is the safest and most reliable emergency source. (CDC)

The Most Important Rule: Never Heat a Sealed Bottle

The safest small distiller operates at atmospheric pressure.

Steam must have an unrestricted path from the boiling pot, through the condenser, and out into an open collection container.

Never:

Heat a tightly sealed stainless-steel bottle
Clamp an ordinary stockpot lid shut
Plug a safety or pressure-release valve
Install a valve in the steam outlet
Submerge the collection tube beneath the collected water
Use a blocked, kinked, or flattened condenser tube
Modify a pressure cooker for this project

Water produces increasing vapor pressure when heated in a closed container. Purpose-built pressure cookers use controlled pressure regulators and emergency-release systems because trapped steam can otherwise create a destructive failure. (USGS)

Use an atmospheric distillation lid or purpose-built steam kettle instead.

What the System Looks Like

The safer layout has four sections:

Boiling pot → unrestricted steam line → cold condenser coil → open collection container

The condenser is placed in a separate bucket of cool water.

Do not wrap the condenser tightly around the hot boiling vessel. A condenser works by removing heat from vapor. Heating the coil with the same flame or hot pot works against the condensation process.

Materials

Atmospheric-pressure boiler

Use one of the following:

Stainless-steel stockpot with a purpose-built distillation lid
Stainless-steel steam kettle designed for atmospheric distillation
Commercial stovetop water-distiller boiler
Stainless pot with a professionally fitted, unrestricted steam outlet

A practical capacity is approximately two to four gallons, although a smaller pot is easier to handle.

The lid must guide steam toward the condenser without turning the pot into a pressure vessel.

Do not use:

An insulated drinking bottle
A vacuum flask
An aluminum beverage bottle
A pressure cooker with altered components
A container with unknown interior coatings
A damaged or corroded vessel

Condenser coil

Ten to twenty feet of soft copper water tubing
Approximately ¼- to ⅜-inch outside diameter
Large plastic or stainless-steel cooling bucket
Water-rated compression fittings
High-temperature food-contact hose, if needed
Stainless-steel hose clamps
Rubber grommet or bulkhead fitting
Cool water
Ice, optional

Not all copper tubing is intended for drinking-water contact. Select new tubing carrying appropriate drinking-water certification rather than reclaimed refrigeration, automotive, or industrial tubing. NSF/ANSI/CAN 61 evaluates health effects from materials that contact drinking water. (NSF)

Joining materials

Use:

Potable-water-rated compression fittings, or
Certified lead-free plumbing solder and flux

Do not use old electronics solder, unknown brazing material, or fittings salvaged from an unidentified system.

EPA requires pipes, fittings, solder, and flux used for water intended for human consumption to satisfy current lead-free requirements. (US EPA)

Collection equipment

Clean stainless-steel container
Sanitized food-grade water container
Clean glass jar for small test batches
Tight-fitting storage lid
Labels and marker

The collection vessel remains open during operation and is covered only after the distillation run has ended.

Tools

Tubing cutter
Tape measure
Drill
Hole saw or step bit
File
Adjustable wrench
Screwdriver
Work gloves
Safety glasses
Heat-resistant gloves
Digital thermometer, optional

Step 1: Form the Condenser Coil

Find a smooth round object approximately six to ten inches in diameter.

A small bucket, metal can, or section of large pipe can serve as the forming guide.

Leave approximately 18 inches of straight tubing at the beginning.

Slowly wrap the tubing around the form, creating an even coil. Do not force the copper into tight turns.

The completed coil should have:

Smooth bends
No kinks
No flattened sections
Space between turns
A continuous downward slope
A straight outlet section at the bottom

Leave another 18 inches of straight tubing after the final turn.

Condensed water must be able to flow downhill through the complete coil. An upward loop or low pocket may trap water and restrict the vapor path.

When the tubing develops a severe kink, replace the damaged section rather than repeatedly bending it back and forth.

Step 2: Prepare the Cooling Bucket

Place the coil inside a large bucket.

The upper connection should remain above the rim. The lower outlet should pass through the bucket wall near the bottom.

Mark the outlet location approximately one to two inches above the bucket floor.

Drill a hole sized for the grommet or bulkhead fitting.

Smooth the edges and remove all plastic shavings.

Pass the condenser outlet through the opening and install the seal. Keep sealant away from the inside of the copper tubing.

Allow every sealant to cure according to its manufacturer’s instructions before operating the system.

Step 3: Stabilize the Coil

The coil must not float or shift when the bucket is filled.

Secure it with:

Stainless-steel brackets
A removable crossbar
Copper-compatible clips
Temperature-appropriate plastic restraints

Leave open space around the tubing so cooling water can circulate between the turns.

The bottom outlet should extend far enough beyond the bucket to drip into the collection container without touching its rim.

Step 4: Prepare the Boiler Lid

The simplest safe option is a commercial atmospheric distillation lid that fits the selected stockpot.

It should include:

An unrestricted steam outlet
Heat-resistant gasket material
A lid that rests or latches as designed
No mechanism intended to create operating pressure
No valve capable of closing the steam path

A fabricated lid should be assembled by someone experienced with food-contact plumbing and steam equipment.

Do not attempt to make the connection airtight by overtightening the lid or adding clamps around the pot.

A small amount of leakage around a nonpressurized lid is less dangerous than a blocked outlet, although leakage will reduce efficiency and can cause steam burns.

Step 5: Connect the Boiler to the Condenser

Connect the boiler’s steam outlet to the upper end of the condenser.

Use either:

A direct copper connection, or
A short section of high-temperature food-contact hose

The connecting line should:

Be as short as practical
Slope toward the condenser
Remain clear of the flame
Avoid sharp bends
Contain no shutoff valve
Have no collapsed sections
Be mechanically supported

Ordinary vinyl hose, garden hose, aquarium tubing, and unidentified clear tubing may soften or collapse when exposed to steam.

Use components rated for the expected temperature and water-contact application. NSF guidance recommends verifying that every plumbing material touching drinking water is certified for that purpose. (NSF)

Step 6: Test the Vapor Path With Cold Water

Before using heat, disconnect the steam line from the boiler.

Slowly pour clean water into the upper end of the condenser.

Water should travel through the coil and flow freely from the outlet.

Look for:

Restricted flow
Leaks
Kinked copper
Upward loops
Loose fittings
Water trapped inside the coil

Correct every problem before reconnecting the boiler.

The outlet must remain fully open.

Step 7: Conduct the First Heated Test With Safe Water

The first test should use ordinary potable tap water—not seawater or questionable surface water.

Fill the boiler no more than approximately halfway.

Leaving generous headspace reduces the risk of foaming or boiling water entering the steam tube.

Fill the condenser bucket with cool water.

Place the open collection jar beneath the outlet.

Connect the steam line and inspect the entire setup.

The boiling pot, cooling bucket, and collection container should all rest on stable surfaces. The condenser should sit lower than the boiler outlet so the condensate flows downhill.

Choosing a Heat Source

A normal kitchen range may be used when the boiler is suitable for stovetop operation and the room is appropriately ventilated.

A propane camping stove, charcoal burner, or outdoor wood stove must be used outdoors only, away from windows, doors, and vents.

Fuel-burning camping equipment can produce carbon monoxide, an odorless and poisonous gas. CDC warns against using camp stoves, grills, and similar combustion appliances inside homes, garages, basements, campers, or other enclosed spaces. (CDC)

Keep the heating system away from:

Children
Pets
Walkways
Dry vegetation
Flammable liquids
Loose clothing
Plastic tubing
The collection container

Keep an appropriate fire extinguisher nearby.

Step 8: Bring the Water to a Controlled Boil

Begin with low or moderate heat.

At sea level, water boils at approximately 212°F. The boiling temperature decreases as elevation increases. The source tutorial’s recommendation of 150°F to 200°F is therefore not a reliable general target for producing steam in an atmospheric system. (practicalsurvivalist.com)

You do not need a violent boil.

A steady, controlled boil is preferable because excessive bubbling may:

Carry salty droplets into the steam line
Cause foaming
Waste fuel
Overwhelm the condenser
Increase burn risk
Boil the pot dry more quickly

Watch the complete system throughout operation.

Never leave it unattended.

Step 9: Watch for Condensation

As steam reaches the cold copper coil, liquid should begin dripping from the outlet.

The time required depends on:

Starting water temperature
Burner output
Pot size
Condenser length
Cooling-water temperature
Ambient conditions

The distilled water should emerge as liquid—not as an uncontrolled stream of steam.

When hot vapor escapes from the collection end:

Reduce the heat.
Replace some warm condenser water with cooler water.
Add ice when available.
Confirm that the complete coil is submerged.
Check for sections of tubing sitting above the cooling bath.

Do not place your face, hands, or body near the outlet while testing.

Step 10: Maintain the Cooling Water

The cooling bath gradually absorbs heat from the steam.

Check it regularly.

For a short run, occasional ice or cool replacement water may be sufficient.

For a longer run, create a simple flow-through cooling bath:

Introduce cold water near the bottom.
Allow warmer water to overflow from the top.
Keep the cooling water completely separate from the distillate.

Do not splash condenser water into the collection container.

The cooling bath is not treated drinking water.

Step 11: Discard the Commissioning Batch

For a newly constructed system, discard the first complete test batch.

This conservative commissioning step helps flush:

Metal particles
Manufacturing residue
Flux residue
Sealant contamination
Dust
Cleaning material

After the system cools, flush the condenser again with safe water and inspect every joint.

Use only properly certified water-contact components. Discarding the initial batch cannot make unsafe materials suitable for drinking-water use. (NSF)

Step 12: Distill Saltwater

After the clean-water test succeeds, the system can be tested with known saltwater.

Use water from a source that is not suspected of containing:

Fuel
Solvents
Industrial waste
Pesticides
Chemical runoff
Radioactive contamination
Unknown oily residue

Do not use water taken near:

Fuel docks
Shipyards
Industrial discharge points
Marinas with visible spills
Storm drains
Sewage outlets

Distillation can remove sodium and many other dissolved substances, but some volatile chemicals can vaporize and pass through the condenser. CDC states that water containing fuel or toxic chemicals should be replaced with bottled water or another source rather than relying on household treatment. (CDC)

Pretreating Cloudy Source Water

When the saltwater contains visible sediment:

Let it settle.
Pour off the clearer upper water.
Pass it through a clean cloth or sediment prefilter.
Add the clarified water to the boiling pot.

This step keeps sand, plant matter, and debris out of the boiler.

Prefiltering does not make the water safe by itself. Its purpose is to reduce fouling and make the distiller easier to clean.

Prevent Saltwater From Entering the Condenser

The vapor outlet should capture steam—not splashing liquid.

Reduce carryover by:

Keeping the pot less than half full
Using moderate heat
Leaving sufficient headspace
Installing a purpose-built splash separator
Keeping the steam outlet above the highest liquid level
Avoiding vigorous boiling

When salty water is mechanically carried into the condenser, the collected product may still contain substantial salt.

Stop the run if liquid surges through the steam tube.

Allow the system to cool, clean the condenser, reduce the fill level, and restart with gentler heat.

Is the Collected Water Automatically Safe?

No homemade device can guarantee the safety of every source.

A correctly operating distiller can greatly reduce:

Salt
Bacteria
Viruses
Parasites
Many dissolved metals
Many nonvolatile chemicals

However, certain volatile organic compounds, volatile solvents, and pesticides may pass through with the vapor. Bacteria may also grow on cooling coils while systems are stored if they are not cleaned and dried properly. (CDC)

The safety of the collected water depends on:

The original source
Materials used in construction
Condenser cleanliness
Whether salty water splashed into the steam line
Collection-container sanitation
Storage practices
Presence of volatile chemicals

Do not judge safety by clarity, smell, or taste alone.

Safe Collection and Storage

Use a clean, sanitized container.

The condenser outlet should drip into the container without touching:

The jar rim
Hands
Dirty tools
The ground
Source-water containers

Cover the water after the run ends.

CDC recommends storing treated water in durable, clean containers with tight covers and avoiding containers that previously held pesticides, petroleum products, or other toxic chemicals. (CDC)

Label the container with:

“Distilled water”
Source used
Processing date
Batch number

Keep it away from direct sunlight and chemicals.

How Much Water Will It Produce?

Do not promise a fixed output.

Production depends on:

Boiler size
Heat input
Condenser capacity
Cooling-water temperature
Steam leakage
Tubing length
Weather
Elevation

A small system may produce only a slow drip or narrow stream.

Distillation is usually energy-intensive and slower than other water-treatment methods. (CDC)

Test your completed system and record:

Starting source-water volume
Final collected volume
Time required
Fuel consumed
Cooling water used
Brine remaining

These measurements will reveal whether the system has a realistic role in your preparedness plan.

Never Let the Boiler Run Dry

Remain beside the distiller and monitor its water level.

Stop heating while liquid remains inside the pot.

Running dry may:

Overheat the vessel
Damage the gasket
ruin fittings
concentrate salt into a hard crust
expose the boiler to extreme temperatures
create an unstable hot surface

Do not open the system immediately after stopping the heat.

Allow the pot, tubing, and condenser to cool completely.

Steam can remain inside hot components after visible dripping has stopped.

Managing the Concentrated Brine

Distillation removes water while leaving most salt behind.

The remaining liquid therefore becomes increasingly concentrated.

Do not continually refill the pot without emptying it.

After each run:

Allow the boiler to cool.
Pour out the concentrated brine.
Rinse the pot.
Remove scale.
Inspect the steam opening.
Begin the next run with fresh source water.

Do not pour concentrated brine onto garden plants, lawns, freshwater streams, septic systems, or metal surfaces.

Dispose of it according to local requirements and the source water’s known contamination.

Cleaning the System

After every run

Empty the boiler.
Rinse away salt.
Flush the condenser with clean water.
Clean the lid and gasket.
Wash the collection container.
Empty the cooling bucket.
Allow all parts to dry.

Periodically

Inspect for:

Mineral scale
Green or blue copper corrosion
Loose fittings
Cracked tubing
Discolored seals
Mold
Unusual odor
Restricted flow

Replace damaged or corroded components.

Do not scrape the inside of copper tubing with steel wire or introduce cleaning chemicals that cannot be completely removed.

CDC notes that microorganisms may grow on cooling coils while distillation equipment is not being used, making regular cleaning and dry storage important. (CDC)

Common Mistakes

Heating a closed steel bottle

A tightly closed vessel can pressurize as steam forms.

Use an unrestricted atmospheric-pressure boiler.

Wrapping the condenser around the hot pot

The condenser must lose heat.

Place it in a separate cold-water bath.

Operating at a claimed 150°F to 200°F target

At ordinary sea-level atmospheric pressure, water boils near 212°F. The temperature is lower at elevation, but there is no universal 150°F-to-200°F desalination setting. (USGS)

Using old copper tubing

Refrigeration and industrial tubing may contain oil, refrigerant, solder, or other contamination.

Use new certified water-contact tubing.

Using electrical solder

Use lead-free plumbing materials intended for drinking-water contact. (US EPA)

Allowing the coil to rise and fall

Trapped condensate can obstruct the vapor path.

Maintain a continuous downhill slope.

Submerging the outlet

The collection end must remain open to the atmosphere.

Do not allow it to sit below the water level in the jar.

Filling the boiler completely

Insufficient headspace allows salty water to splash into the condenser.

Begin below half capacity.

Using chemically contaminated water

Distillation does not reliably remove every volatile chemical.

Use another approved water source when fuel or toxic contamination is suspected. (CDC)

Leaving the system unattended

A blocked tube, overheated boiler, empty cooling bath, or dry pot can become dangerous quickly.

Optional Improvements

Use a stainless-steel condenser

Stainless tubing is durable and avoids some copper-related water-chemistry concerns.

It is more expensive and harder to form.

Add a splash separator

A purpose-built separator between the boiler and condenser can help prevent droplets of saltwater from entering the vapor line.

It must not restrict the open steam path.

Add continuous condenser cooling

A lower cold-water inlet and upper warm-water overflow can improve condensation during longer runs.

Add temperature monitoring

Thermometers can help track the boiler and condenser, but they do not replace an unrestricted steam outlet or continuous supervision.

Add a certified carbon stage

A certified activated-carbon treatment stage may reduce specified volatile organic chemicals.

Carbon performance varies by product and contaminant, and the cartridge must be replaced according to its rating. EPA recognizes granular activated carbon as an established treatment for many VOCs. (US EPA)

Do not place loose barbecue charcoal in the collection container.

Is This Project Worth Building?

Yes—when it is approached as a small, carefully monitored desalination experiment.

Its advantages include:

Simple operating principle
No replacement filter media
Removal of dissolved salt
Use with several heat sources
Easy-to-observe operation
Valuable hands-on preparedness experience

Its limitations include:

High fuel demand
Slow production
Steam-burn risk
Need for continuous supervision
Regular cleaning
Limited chemical protection
Potential material-contamination problems
No independent performance certification

Build it before an emergency.

Test it with safe tap water.

Inspect every fitting.

Measure the output.

Practice cooling and cleaning it.

A small system that has been safely tested is more useful than an impressive-looking device assembled for the first time when drinking water is already scarce.

Final Safety Note

This distiller must operate at atmospheric pressure.

Never heat a tightly sealed bottle, alter a pressure cooker, block a steam outlet, install a shutoff valve in the vapor path, or submerge the condenser outlet.

Use only materials rated for hot drinking-water contact. Steam, boiling brine, hot copper, and heated metal can cause severe burns.

Distillation can remove salt, germs, and many nonvolatile contaminants, but it cannot make every chemically contaminated source safe. Never process water suspected of containing gasoline, solvents, pesticides, toxic industrial chemicals, or radioactive material.

Use bottled or officially approved water whenever it is available.