Membrane Flush and Winterization Guide
Freshwater rinse, long lay-up and end-of-season protection
During production your watermaker membrane is exposed to seawater under high pressure. Salt left in the circuit after a run reduces output and shortens life — freshwater flushing limits that risk. If the unit will be unused for more than 4 weeks, winterisation is required to prevent bacterial growth inside the membranes, as stated in our FAQ.
Flushing and winterisation are different tasks: one is in-season routine, the other protects during long lay-up. For the full maintenance calendar see Watermaker Maintenance Guide; for step-by-step lists see the end-of-season and pre-season checklists.
Quick Rules
- Freshwater flush after production
- Lay-up 4+ weeks → lay-up chemical
- Tune auto flush to your profile
- Book on-site service for season closing
Flush vs Winterisation — What's the Difference?
| Freshwater flush | Winterisation (lay-up) | |
|---|---|---|
| Purpose | Reduce salt build-up in the membrane circuit | Prevent biofouling and drying during long idle periods |
| When | After each run or at regular intervals | Unused more than 4 weeks — FAQ |
| Supply | Onboard fresh water / dock supply | Lay-up chemical + preservative application |
| Duration example | Short rinse (5–10 min routine; 15 min at season end) | End-of-season checklist steps |
| Materials | Fresh water only | Lay-up chemical from stock |
Short marina or anchorage breaks (under 4 weeks) usually need flushing only, not full winterisation. When approaching the limit, planning service is safer.
Freshwater Flush — How Often and How?
Flushing circulates fresh water through the membrane and pressure path to remove salt residue. Missed flush is listed among causes of early membrane failure in our spare parts guide — replacement schedule.
Manual flush
If auto flush is off or you need an extra rinse on a short stop: stop production and run fresh water through the membrane circuit for 5–10 minutes.
Flush and check quality before sending product water to the tank — water tank + watermaker planning.
Automatic reverse flush (auto flush)
SCW-30 has automatic reverse flush with timed re-flush. On SCW-100 and larger models, reverse flush can be scheduled or disabled by the user to optimise membrane cleaning.
Even with auto flush enabled, dirty pre-filters or a blocked brine line do not replace proper maintenance — maintenance guide.
At anchor on 12V
Post-production flush must not be skipped on 12V systems running from solar. Long continuous runs load both the battery bank and the membrane — plan a sensible operating window — 12V + solar panel guide.
Which Task When?
Daily / each run
Short fresh flush or auto flush. Brine discharge open.
1–3 week break
Extended flush before last run; filter check. Full winterisation not required.
Season end
15 min flush, drain, preservative, filter removal — checklist.
Winterisation Steps (End of Season)
The flow below matches the end-of-season checklist. Chemical dosing and exact sequence depend on your model and are confirmed during service or from the operating instructions — applied together at a booked visit.
- Final freshwater flush — checklist recommends 15 minutes.
- Stop and drain the system — depressurise safely.
- Apply preservative — lay-up chemical (pickling solution) protects the membrane.
- Remove or replace pre-filters — stored filters can foul.
- Isolate power — per unit instructions.
- Book service — especially for wintering boats from October onwards.
Full list: End-of-Season Winterization Checklist.
Season Opening — After Lay-Up
Our FAQ lists pre-season preparation as a separate periodic task. Checks aligned with the pre-season checklist:
| Check | Why |
|---|---|
| Lay-up / preservative drained? | Residual chemical affects production and taste |
| Pre-filters renewed? | Filters stored over winter are inefficient |
| HP pump oil level | 250-hour rule — maintenance guide |
| Electrical connections | Moisture and vibration can loosen contacts |
| Brine reject valve free? | Common fault source — common mistakes |
| Test run + TDS | Checklist: ~15 min test and TDS reading |
| Leak inspection | HP pump and hose connections |
If TDS stays high after testing, try extra flush or filter replacement; if the issue persists, call for service — pre-season checklist.
Mistakes to Avoid
Our first-time user guide lists flush and winterisation errors that directly affect membrane life.
Full list: First-Time Watermaker Mistakes.
Frequently Asked Questions
Related Guides
Watermaker Maintenance Guide · End-of-Season Checklist · Pre-Season Checklist · Spare Parts Schedule · All Guides
Plan End-of-Season Lay-Up On Site
Membrane cleaning, filters and lay-up chemical — one appointment
Book an Appointment Call: +90 252 412 90 78