One of the most common questions we get from new and prospective watermaker owners is for more information on the flushing, pickling and maintenance of the Reverse Osmosis Membranes.

Whilst it is correct that the care of your membranes is certainly the most important part of watermaker ownership – by maintaining them correctly you will get years and years of use from them before they require replacement.

The good news is that the maintanance of a Rainman Watermaker membrane is exceedingly simple, and takes only a matter of minutes prior to storing your equipment….. Here is a chart to go by – follow this and you will be following our best practices for optimum membrane health…

With RO membranes, if you are using them daily, then no flushing or pickling is required – the constant flow of water will provide enough movement to keep your membranes clean an d trouble free – however a number of owners do choose to fresh water flush there membranes at the end of each use just as a good practice. 

If you do not plan to use your membranes for 3-6 days, we recommend a freshwater flush
​(same procedure as in the video – just with no picking solution added to the bucket)
If you do not plan to use your system for 7 days or more, we recommend that you pickle your system. 

Check out this quick video where i go over both flushing and pickling your system!

Step by Step Instructions

Fresh Water Flush

​We recommend flushing your desalinator with fresh water after every use to prevent biological fouling and to rinse salt from the entire system. 

1. When the freshwater tank is full, remove the product water hose and fill an open container of water with approximately 10 liters (2.5 gallons) of freshwater.

2. Open the pressure control valve completely and switch off the unit. Remove the intake hose from the source water and place it in the open container of freshwater. Start the unit again, and with the pressure control valve remaining open, run the entire contents through the

3. When the bucket is almost empty, switch off your desalinator, leaving the freshwater in the system.

Never allow the bucket to run dry while the pump is running. You will damage the unit.
Never flush your desalinator with water containing chlorine, which will damage the membranes. That includes town or tap water, which contains chlorine, or water from a vessel’s tanks, which also may contain chlorine. Chlorine damages RO membranes.
If you plan on not using your watermaker within the next few weeks, you’ll need to pickle the membranes.


Pickling fills the membrane housings with a biocide that prevents fouling.

Once pickled, membranes can be stored for six months or more.

1. To pickle your desalinator, add 5 tablespoons of Sodium Metabisulphite (SMBS) to a 10 litre (2.5 gallon) bucket of fresh water, to make a 1-1.5% solution of SMBS. After opening the pressure control valve completely, switch off the unit, remove the intake hose from the source water and place it in the open container of fresh water. Start the unit again, keeping the pressure control valve open and run the entire contents through the system.

2. When the bucket is almost empty, switch off your desalinator, leaving the pickling fluid in the system.
When storing the unit for more than a month, discard the prefilter and drain the pre-filter housing.
Your desalinator is now pickled and can be stored for up to 6 months.

Never allow the pickling solution bucket to run dry while the pump is running. You will damage the unit.

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