Work out how much water the boat really uses, how many litres an hour you need for the generator time you are willing to give it, and which Spot Zero capacity fits — with a margin for 50 Hz power and membrane ageing.
Capacities are Spot Zero’s rated US gallons per day, converted at 3.785 L per gallon and divided by 24 for litres per hour. Real output varies with water temperature, salinity and feed pressure; warm Thai water helps, 50 Hz power takes a little back. We confirm the sizing with the factory for your boat before you order.
How to read the result
Gallons per day is a 24-hour figure, so the honest number is litres per hour against the hours you will actually run the system. A 600 GPD watermaker makes about 95 litres an hour; four hours a day gives 380 litres, which is a frugal crew of six or a comfortable couple. A 1,200 GPD system doubles that. Charter boats and boats with guests should size on the comfortable or guest figures, not the frugal one — nobody complains about too much water.
Wash-down water only counts against the watermaker if it comes from the tanks. If you want it spot-free — the point of a Spot Zero — it is purifier capacity: a purifier polishes dock water or watermaker water, so on a marina-based boat it may be the only machine you need.
What the margin is for
Thailand is 230 V 50 Hz. Spot Zero builds for 50 or 60 Hz and notes that production can be a little lower at 50 Hz because the pump motor turns slightly slower; membranes also lose a little output as they age. The 15 % margin keeps the system off its limit for both. Warm tropical seawater works the other way — membranes pass more water at 29 °C than in the cold conditions they are rated in — so a correctly sized system here usually has some in hand.
Next step
Send us the result with the boat’s length, tankage and where she is kept, and we will confirm the capacity with the factory, specify the 50 Hz configuration, and quote the equipment with the lead time: LINE @drakeco, WhatsApp +66 99 406 4680 ou e-mail. Parts for every system are in the watermaker parts section, and the service guide covers what it costs to run.