Pickling yacht watermaker membranes for storage

Leaving seawater inside a watermaker can promote mineral adhesion, biological decay, biofouling and low-oxygen corrosion. A fresh-water flush limits these problems, but it does not replace the prescribed preservation procedure for a longer shutdown.

The correct decision depends on the watermaker, its fitted options, the planned shutdown and the manufacturer's storage chemistry. This guide compares the cited Spectra Ventura and EchoTec DML instructions, then covers preservation, recommissioning and the checks crew can make safely.

Choosing between flushing and pickling

A fresh-water flush is the normal step after production. Spectra recommends flushing its watermakers after every use, while the Ventura and EchoTec manuals set different limits for how long a flushed machine may remain idle.

Pickling, also described as membrane preservation or chemical storage, is for shutdown periods beyond the flush-only allowance in the relevant manual. The figures below belong to the named systems and must not be transferred to another make or model.

For an EchoTec DML, a shutdown of up to ten days can be covered by a fresh-water flush. The flush can also be repeated instead of placing the membrane into chemical storage. Beyond ten days, its manual specifies preservation with the stated biocide and says that treatment protects the membrane for up to ten months.

A fresh-water-flushed Spectra Ventura may be left for up to five days without further action. The manual gives 30 days where the optional Z-ION is fitted. For longer storage under the cited Ventura procedure, fresh-water flush first and then circulate SC-1 storage solution; the manual gives six months of protection.

Treat these dates as model-specific limits. If the yacht's wider machinery is also being shut down, coordinate the watermaker work with the Mallorca winter lay-up checklist.

Setting the fresh-water flush correctly

The flush must follow the manufacturer's procedure rather than an assumed duration. On a Spectra Ventura 150/200T, the default fresh-water-flush duration is three minutes, but the owner should calibrate it to the particular installation.

During calibration, collect brine while the flush is running and check it with a handheld salinity meter. The Ventura manual treats the system as fresh-water flushed when brine salinity falls below 1,000 ppm. Set the flush time according to that result rather than relying on the default alone.

After every production run:

• Run the specified flush. Spectra's general guidance calls for a fresh-water flush after every use.
• Confirm the Ventura setting. Use the below 1,000 ppm brine criterion when calibrating a Ventura 150/200T installation.
• Record the work. Enter the production run and completed flush in the machinery log so the next shutdown decision is based on the last use date.

Fresh-water flushing matters because it reduces the period for which seawater remains in the system. Spectra links this with limiting mineral adhesion, biological decay, biofouling and low-oxygen corrosion.

Using the correct preservative without pressurising the system

There is no universal watermaker pickling chemical. Use only the preservation chemistry approved for the particular machine. Spectra specifically warns that storage chemicals containing sodium metabisulfite can permanently damage its Clark Pump and membrane end plugs.

For the cited Spectra Ventura procedure, fresh-water flush the machine before introducing SC-1 storage solution. Circulate the solution with the system unpressurised. The Clark Pump pressure-relief valve must be opened half a turn during this cycle, otherwise membrane damage can result.

The safe planning points are:

• Identify the exact system. Confirm the make, model, fitted options and the storage procedure in its manual.
• Check the shutdown period. Compare the planned lay-up against the flush-only allowance for that system.
• Use only the specified chemistry. Do not substitute a general biocide or another brand's storage product.
• Keep a Ventura unpressurised. Open its Clark Pump pressure-relief valve half a turn when circulating the storage solution.
• Stop if the procedure cannot be completed. A pressure-relief, valve, control or chemical-handling fault requires engineering attention.

Do not use membrane cleaning as a routine response to a storage or water-quality concern. Spectra says unnecessary cleaning can be detrimental to the membrane and shorten its life.

Restarting after membrane storage

Recommissioning also depends on the preservation method and watermaker model. Do not assume that one purge duration applies across different systems or storage chemicals.

After EchoTec membrane storage, discard at least the first 30 minutes of product water before using it for drinking or food. If product water remains unacceptable after the manufacturer-directed purge, stop treating the issue as a normal storage restart and call an engineer.

A Spectra Ventura that has undergone long propylene-glycol storage needs a different process. Its manual directs the operator to flush the system with the pressure-relief valve open for four to six hours before judging water quality.

If output or salinity is still abnormal after the prescribed recommissioning process, use the watermaker output and salinity guide to frame the symptoms. Do not start an unnecessary membrane-cleaning cycle as a diagnostic shortcut.

What crew can check safely

Crew checks should establish whether the machine was flushed, how long it has been idle and whether the correct storage procedure can be followed. They should not involve substituting chemicals or bypassing a pressure-relief or control fault.

• Log every flush. After each production run, carry out the maker-specific fresh-water flush and record it in the machinery log.
• Calibrate a Ventura flush. Collect flush brine with the system running its flush cycle, use a handheld salinity meter and apply the manual's below 1,000 ppm completion criterion.
• Check the last use date. Before lay-up, compare the planned shutdown with the interval stated for the exact machine and fitted options.
• Recognise the EchoTec limit. An EchoTec DML stored beyond ten days requires its preservative procedure rather than relying on the previous flush.
• Check the Ventura pressure condition. Do not pressurise a Spectra Ventura while circulating storage chemical. Its pressure-relief valve must be open half a turn.

If the shutdown plan changes after preservation, review the protection period stated for that exact procedure. The cited EchoTec treatment and Spectra SC-1 procedure have different storage periods.

When to call an engineer

Call an engineer when contamination, a mechanical fault or unacceptable product water takes the job beyond the prescribed crew procedure.

• Unapproved preservative was introduced. This is particularly serious on Spectra equipment because sodium metabisulfite storage chemicals can damage the Clark Pump and membrane end plugs.
• The membrane was exposed to contamination. Engineering assessment is needed following exposure to chlorinated flush water, oil, fuel or other chemical contamination.
• Product water remains unacceptable. Escalate the fault if quality has not recovered after the manufacturer's purge or extended post-storage flushing instructions.
• The storage cycle cannot remain unpressurised. A pressure-relief, valve or control fault that prevents the prescribed procedure needs attention before preservation continues.
• Chemical handling cannot follow the manual. Do not improvise with another preservative or a modified circulation process.

Blueward Marine in Palma provides yacht watermaker service, and crew can book a service online, describe the fault and upload photos for a structured technical intake. For urgent assistance in Mallorca, call the 24/7 emergency line on +34 971 251 374.