Planning Water Tank Capacity With Your Watermaker
Plan tank volume and hourly output together — sustainable water balance at anchor
Most buyers focus only on watermaker capacity; yet your onboard fresh water tank is part of the same equation. The tank is ready reserve; the watermaker is daily production capacity. Without planning both together, the tank empties after a few days at anchor — or an oversized unit gets chosen.
Calculate daily litres in our yacht capacity guide and model selection in product selection guide.
Two Roles
Tank: Buffer — reserve between production runs
Watermaker: Production — fills the tank at anchor
Planning Formulas
1 — Daily balance (anchor routine)
Tank + daily production ≥ daily consumption
Daily production = hourly output × run time
Example: 200 L tank + SCW-50 (50 L/hour) × 3 h = 200 + 150 = 350 L/day available; 140 L/day use → balance holds.
2 — Run time
Daily need ÷ hourly output = hours/day
Example: 140 L ÷ 50 L/hour = 2.8 h/day. Our capacity guide targets 2–5 hours/day.
3 — Multi-day anchor (no marina)
Total need = daily use × number of days
Total supply = full tank + (daily production × days)
Total supply must ≥ total need. A smaller tank needs higher daily production.
4 — Is tank alone enough?
If tank capacity exceeds daily need and you take marina water every night, a watermaker is not mandatory (capacity guide FAQ). Long anchoring and bay cruising favour a watermaker for independence.
5 Steps to Plan Tank + Watermaker
Write daily consumption
Crew count × litres/person/day. Use the table in our capacity guide.
Note current tank volume
Single or multiple tanks? Do you leave port with full tanks?
Define anchor scenario
How many days without marina water? When will you run the unit?
Model and run time
Calculate daily production from L/hour; aim for 2–5 hours/day.
Confirm at survey
Tank connection (product pages list 8 mm tank inlet), location and power are reviewed on site.
Example Planning Scenarios
Aligned with consumption examples in our capacity guide.
4 crew sailboat — 3 days at anchor
~140 L/day → 420 L over 3 days.
200 L tank (full) + SCW-50 3 h/day (150 L/day production).
End of day 1: 200 + 150 − 140 = 210 L in tank
Result: Balance holds. Tank buffers; watermaker closes daily gap.
4 crew — small tank, SCW-30
100 L tank, ~140 L/day need, SCW-30 3 h/day (90 L production).
Result: 100 + 90 − 140 = 50 L — tank drops daily. Longer run time, larger tank or SCW-50 reviewed during survey.
8 crew motor yacht — generator at night
~360 L/day, 500 L tank, SCW-150 ~2.5 h on generator (375 L).
Strategy: Fill tank during generator hours; consume by day. Large tank as buffer; high output in short runs.
Marina nights + daytime bays
Marina water fills tank overnight; watermaker supplements at anchor by day.
Note: With shore power, overnight 230V production may apply — power selection guide. Routine planned at survey.
Water Management Strategies at Anchor
Morning production
On 12V boats, run during daylight with solar — solar panel guide.
Generator hours
230V models (SCW-100–350) run while generator is on; tank fills quickly.
Tank level monitoring
Sensor or manual check; adjust run time accordingly. SCW-50 shows flow on touchscreen panel.
Marina + watermaker
Marina fills the tank; watermaker supports long anchoring. Hybrid use is common on many profiles.
Flush before tank fill
Fresh-water flush after production. SCW-50 automatic salinity rejection directs suitable water to the tank.
Bigger tank or watermaker?
For long anchoring, watermaker gives flexible production; tank is buffer only. Tank enlargement needs space — assessed during survey.
Frequently Asked Questions
Let's Plan Your Tank and Watermaker Together
Tank volume, consumption and model assessed together during survey
Book an Appointment Call: +90 252 412 90 78