Can you use a marine watermaker on a 4WD or caravan?

Yes — portable 12 V units are used for coastal touring. You need a seawater or brackish source and a battery bank that can supply the current, which is typically 15 to 20 amps at 12 V on the small units.

Will a watermaker purify river or tank water?

Reverse osmosis systems on this site are designed for seawater. Using one on fresh, silty or contaminated water is a different application with different pre-treatment, and you should ask the manufacturer before assuming it is suitable.

How much power does a portable 12V watermaker use?

The small units in our table draw a couple of hundred watts, which is roughly 15 to 20 amps at 12 V. Over an hour and a half that is a meaningful share of a touring battery bank, so plan for it.

By vessel · updated 5 September 2026

Watermakers for RVs, caravans and 4WDs

Reverse osmosis is not only a boat technology, and portable 12 V units are increasingly used for coastal touring and remote camping. The physics does not change, and neither do the constraints — you still need a water source, and you still pay in amps.

Typical daily need30 L2 aboard at 15 L each

What to optimise forFits and stowson this kind of boat

Shortlist leaderLEDI Scout SW201.5 h and 300 Wh for 30 L

The power reality. A touring setup usually has a modest lithium bank and a portable panel. That puts the small 12 V units in scope and everything larger out of it.

What matters on RVs, caravans and 4WDs

You still need a source

A watermaker makes fresh water from seawater or brackish water. It is not a substitute for carrying water inland, and it is not a purifier for suspect town supply.

Amps, not watts, are the limit

A 200 W draw at 12 V is around 17 amps. That is significant on a touring setup and needs proper cable and a bank that can supply it.

Weight and packing

These units are heavy for their size. Check where it lives in the vehicle and who lifts it.

Prefilters and beach sand

Drawing from the surf line loads filters fast. A settling container or a deeper intake makes a real difference.

Shortlist for RVs, caravans and 4WDs

Every system in our table that suits RVs, caravans and 4WDs, ordered by fits and stows. Run time and energy below are for 30 litres a day.

System	Power	Output L/hr	Draw W	Wh per litre	Price
Scout SW20 LEDIreported	12V DC	20	200	10.0	on request
Portable 24VDC 55L Rainman	24V DC	45–61	600	11.3	$4,898
Portable 12VDC 34L Rainman	12V DC	26–37	400	12.7	$4,898

Under 6 Wh/L · energy recovery

6–12 Wh/L

Over 12 Wh/L

Check it against your own boat

Enter your crew, battery bank and daily solar surplus and we will show which of these actually fit.

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Common questions

Can you use a marine watermaker on a 4WD or caravan?: Yes — portable 12 V units are used for coastal touring. You need a seawater or brackish source and a battery bank that can supply the current, which is typically 15 to 20 amps at 12 V on the small units.
Will a watermaker purify river or tank water?: Reverse osmosis systems on this site are designed for seawater. Using one on fresh, silty or contaminated water is a different application with different pre-treatment, and you should ask the manufacturer before assuming it is suitable.
How much power does a portable 12V watermaker use?: The small units in our table draw a couple of hundred watts, which is roughly 15 to 20 amps at 12 V. Over an hour and a half that is a meaningful share of a touring battery bank, so plan for it.

Guides that go deeper

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How the shortlist is built. 30 litres a day is 2 aboard at 15 litres each — a planning figure for this kind of boat, not a measurement of yours. The list is filtered to systems whose power source suits RVs, caravans and 4WDs and ordered by fits and stows. Every figure is the manufacturer’s rated output and draw; Wh per litre is one divided by the other. Methodology.