Installing a Watermaker: What's Actually Involved
Watermaker install is among the most common cruiser DIY projects. The cost savings vs professional install are substantial (USD 2,000–5,000), and the systems are straightforward enough that cruisers with basic plumbing and electrical skills can handle it. The catch: it touches several boat systems, and getting any one of them wrong is a problem.
What's involved
- Through-hull and intake: Dedicated sea cock and strainer. Cleanest install is a new through-hull (haul-out required) or a tee off existing engine intake (in-water possible but limits).
- Pre-filtration: Sediment filters, carbon filter, plumbing.
- Pump and motor: Mounting location with vibration isolation, ventilation.
- Membrane housing: Mounting (horizontal preferred), brine and product discharge.
- Electrical: Fuses, control panel, switches. Lithium-aware wiring if applicable.
- Product water: Pipe to tank (with diverter valve for first-flush waste).
- Brine discharge: Above waterline preferred; below waterline acceptable.
- Pickling and cleaning: Plumbing for biocide pickling during layups.
Time estimate
DIY install on a 40-footer: 25–40 hours over 5–10 days. Most of the time is figuring out routing through tight spaces, not the actual mechanical work.
What cruisers report
- The mounting location decision is critical and hard to undo
- Verifying every electrical connection prevents future fault-finding
- Test in fresh water first (no salt) to verify plumbing
- First commissioning in seawater always reveals one issue
- Documentation while you install pays back many times
Where to install
- Engine room is common but heats up the unit
- Under the saloon settee — popular but requires clever plumbing
- Aft cabin closet space — limits access but works
- Dedicated locker for the pump module — best when space allows
Cost breakdown (mid-range Spectra 380C or similar)
| Item | Range (USD) |
|---|---|
| Watermaker kit | $4,500–7,500 |
| New through-hull (if needed) | $80–200 |
| Plumbing parts | $200–400 |
| Electrical (wiring, fuses) | $150–350 |
| Mounting brackets | $80–250 |
| DIY total parts | $5,000–8,700 |
| vs Pro install all-in | $7,000–13,000 |
Frequently asked questions
DIY feasible?
Yes, for cruisers with basic skills. 25–40 hours over 5–10 days.
Through-hull needed?
Cleanest install yes. Tee off engine intake possible but compromises.
Mounting location?
Engine room common; settee or locker also work. Cool, ventilated, accessible.
Savings vs pro?
USD 2,000–5,000.
Common mistakes?
Mounting location committed too early; electrical undersized.