Size the watermaker for full occupancy on a hot week with one unit out of service, and keep enough tankage to finish a trip without production. Guests on a dive boat shower after every dive, whatever your consumption assumptions say. Running out of fresh water does not end a trip safely — it ends it embarrassingly, which for a charter operation is worse.
What guests actually consume
Design assumptions in this market are routinely optimistic. Between showers after each dive, rinsing gear, laundry, galley use, and crew consumption, real usage per person per day on a warm-weather dive boat is considerably higher than a cruising yacht’s planning figure. Add crew, who use water all day, and add the boat itself for deck washdown and rinsing.
The honest way to size this is to take your maximum guest and crew complement, apply a generous per-person figure that reflects a hot climate and a dive operation, and then check the result against how long you can run without production if the unit fails.
Redundancy versus tankage
There are two ways to survive a watermaker failure: a second unit, or enough tankage to complete the trip. Both cost space and money, and the right answer depends on trip length.
On short round trips from Labuan Bajo, generous tankage is often the more economical insurance — you can complete the trip on stored water and repair alongside. On longer itineraries out toward Alor or Banda, tankage sufficient for a full trip becomes a large volume and weight penalty, and a second production unit starts to look sensible. Note that tankage volume competes directly with fuel and with accommodation for the same hull space, and that added weight low in the hull affects draft — see optimal draft.
Energy cost
Reverse osmosis is energy intensive, and its demand has to appear in your electrical load calculation rather than being discovered later. On boats trying to reduce generator running hours for guest comfort, the watermaker is one of the loads that forces the generator on. Options include running it during periods when the generator is already loaded for other reasons, energy recovery systems that reduce specific consumption, and on vessels with substantial solar and battery capacity, running production from stored energy. See generator sizing and solar and battery systems.
Feed water quality — the operational trap
Membranes are damaged by sediment, oil and biological load. A liveaboard anchored in a shallow bay over sand, with the tender running nearby and other boats around, is drawing exactly the feed water that shortens membrane life. The practical rules are: do not run production in shallow, turbid or busy anchorages, run it underway in clean deep water wherever possible, fit adequate pre-filtration and actually change it, and flush the system properly whenever production stops.
Crew discipline on this is worth more than an expensive membrane. Most premature membrane failures we see are the result of running production somewhere convenient rather than somewhere clean.
Installation details that matter
- Dedicated raw water intake, not shared with engine cooling, positioned away from discharges and the tender’s operating area.
- Accessible filtration so changing pre-filters is a two-minute job rather than a contortion, because a filter that is hard to reach is a filter that does not get changed.
- Automatic fresh water flush after shutdown, which removes the single largest cause of avoidable membrane deterioration.
- Product water quality monitoring with automatic diversion, so out-of-spec water never reaches the tanks.
- Tank arrangement in more than one compartment, so contamination or a leak does not lose the entire supply.
Water and compliance
Fresh water production interacts with waste handling, because water in becomes grey and black water out. Holding capacity has to match consumption and trip length, and discharge inside the park is regulated — see Komodo National Park compliance and grey and black water treatment. Specifying a generous watermaker without matching holding capacity simply moves the problem.
The full derivation from operating profile to system numbers is on the specification guide.
Frequently asked questions
How much water does a Komodo liveaboard need per day?
More than cruising-yacht planning figures suggest. Guests shower after every dive, gear and decks are rinsed, laundry runs, and crew consume all day. Size on maximum complement with a generous per-person figure for a hot climate and a dive operation, then check survivability with production offline.
Should I fit two watermakers or more tankage?
Trip length decides. On short round trips from Labuan Bajo, tankage sufficient to complete the trip is usually the more economical insurance. On long itineraries toward Alor or Banda that volume becomes prohibitive and a second production unit makes more sense.
Why do watermaker membranes fail early on liveaboards?
Almost always feed water quality. Running production in shallow, turbid or busy anchorages loads the membranes with sediment and biological material. Run in clean deep water underway, fit and actually change pre-filtration, and ensure automatic fresh water flush after every shutdown.
Talk to the build desk
Send the vessel details or the operating profile you want to run and we will tell you what has to be established before a number means anything. Quotations in USD. Construction, repair, refit and vessel-sale contracts are issued by PT Komodo Galangan Nusantara.