Does A Watermaker Affect A Catamaran's Performance Or Weight?

Every catamaran owner learns quickly that weight is the enemy of good sailing. Load a cat too heavily and it sits lower in the water, slows down and starts to feel sluggish in a seaway. So before adding new gear, it makes sense to ask what it will cost you in speed and comfort.

Below we look at why weight matters so much on multihulls, how much a typical system really adds and how making water onboard can actually reduce the load you carry. We also cover smart placement for balance and trim.

Why Weight Matters So Much on a Catamaran

Catamarans rely on light displacement and slim hulls for their speed. Unlike a ballasted monohull, which simply settles a little deeper when loaded, a cat feels every extra kilo. Its hulls sink lower, wetted surface area grows and the boat loses some of the lively acceleration that drew you to multihulls.

Extra weight also affects comfort. As a catamaran sits deeper, the gap between the water and the bridgedeck shrinks, which can mean more slamming upwind or in a short chop. Weight carried far forward or aft makes this worse by encouraging the bows to pitch.

This is why experienced multihull sailors watch their payload closely. Every item that comes aboard, from spare anchors to provisions, adds up over a season. Fresh water is one of the heaviest things on any cruising boat, so it deserves careful thought when you plan your setup.

How Much Weight a Watermaker Really Adds

Modern reverse osmosis units are far more compact than many sailors expect. Smaller 12 or 24 volt systems built for cruising boats often weigh about the same as one or two full jerry cans. Larger units for long-range cats still sit comfortably within a sensible payload.

A complete installation includes a few parts beyond the main unit. You will have a high-pressure pump, membrane housings, pre-filters, a control panel and the plumbing to connect it all. Many systems are modular, so these components can be spread around the boat rather than packed into one spot.

Added together, the impact of a watermaker on catamaran weight is modest. A compact system often weighs less than a few days’ worth of water for a crew of four. That makes it one of the lighter upgrades you can make for the independence it brings.

Trading Heavy Tankage for Onboard Production

Water weighs roughly one kilogram per litre (about 8.3 pounds per US gallon). A catamaran carrying 600 litres in its tanks is hauling around 600 kilograms before anyone steps aboard. That is a serious load for a boat that depends on staying light.

With a watermaker onboard, you no longer need to fill every tank to the brim before leaving port. Many owners sail with tanks partly full and top up as they go, knowing fresh water is only a few hours of running time away. Some even fit smaller tanks during a refit to free up space.

The result is that a catamaran watermaker often leaves the boat lighter overall. Shedding a few hundred kilos of stored water helps your cat sit higher and accelerate more easily in light winds. You also skip marina detours just to fill up, saving diesel.

Smart Placement for Balance and Trim

Where you install the system matters as much as what it weighs. The ideal spot is low down and close to the centre of the boat, often under a berth or in a locker near midships. Keeping weight out of the bows and away from the stern helps the boat stay level.

Balance between the hulls is worth considering too. If your generator or battery bank sits on one side, placing the watermaker in the opposite hull helps even things out. Modular components make this much easier.

The seawater intake deserves attention as well. A flush through-hull well below the waterline keeps drag to a minimum and gives the pump a steady supply in a seaway. With a neat install like this, the effect of a watermaker on catamaran performance is a positive one.

In Summary

A watermaker adds only modest weight to a catamaran, and in practice it often makes the boat lighter by letting you carry far less water. Installed low and central, the system has little effect on trim, while the freedom it brings can improve how and where you sail.

At Eco Sistems USA, our reverse osmosis watermakers draw on more than 20 years of design experience, with energy recovery technology that cuts electricity use by up to 80%. With capacities from 25 to 4,000 litres per hour and more than 80 distributors worldwide, we can match a system to your catamaran. Get in touch today for a free quote on our marine watermakers.