The Plus unit is the ideal water softener for boats up to 70'. This unit will soften an average of 2500 gallons of average hard water (8 grains of hardness), before it needs to be simply recharged.
Considering "normal" usage, a WetSpot Plus will need to be recharged about every 2 months, this is an estimate and is based on washing a 70' boat 2 times per week and filling your on-board fresh water tanks once.
If your boat is traveling to destinations that have consistent hardwater on a regular basis (i.e.-the Bahamas or South America), you may consider using a WetSpot Heavy Duty, as it will require less recharging.
Specifications: 34"L x 10.5" H x 7.25" D 35 lbs. dry