I found this very interesting article on how to pickle your water maker and given the comments on WhatsApp recently it could well prove helpful to some folk. The article if applicable to both Schenker and Spectra water makers (and some others)
Getting PG (propeleyne glycol in the USA is a breeze but could not find it anywhere in the Caribbean (other than St Martin ) or the Bahamas. I have yet to look for it in the Med but if anyone has found it there please let me know. The section in blue italics has been added by your truly as I felt it could do with some additional explanation!
Pickling a Water Maker
What you need to know and rumours you need to Ignore.
There is a Cruiser Myth and dock rumour out there that says pickling a watermaker for prolonged periods of inactivity damages or shortens membrane life. However, the truth is that an Improperly pickled watermaker or one left Improperly laid up for storage is really the greater risk to your watermaker, not one that has been properly pickled. The first reality is that the term pickling sounds old fashioned and mysterious. So why are you Pickling? What is it’s Purpose? And How should it be properly done?
Firstly, Pickling is just the process of pulling in a food grade sterilizing agent to kill the biological life inside your system: Bacteria, Plankton, and Algae.
If a watermaker is left to sit more than 7-10 days without a change of water sitting inside the system or a Sterilization (Pickling), these biological organisms can grow and foul the system. They do this by using all of the Oxygen in the water and then they die. Once dead, their bodies begin to rot and are eaten by the anaerobic bacteria that give off hydrogen sulfide gas (the rotten egg smell) as their metabolic waste, fouling the watermaker. pH changes of the water will also cause scale to precipitate out and further foul your membranes. These precipitates can also plug and damage the internal moving parts of your watermaker. So the pickling agents, either Sodium or Potassium Metabisulfite for piston pump watermakers or a Citric Acid based pickling agent for Energy Recovery Pumps, kill and sterilize the system, protecting is from biological growth and fouling.
As an alternate to Pickling, most watermakers these days have Automatic fresh water flushing that will do a fresh water volume change-out of your watermaker every 5-7 days. When using the Automatic fresh water flushing you don’t need to Pickle the watermaker. The watermaker can sit indefinitely with just fresh water flushing. However, when boats are being left for months rather than weeks with the ships systems decommissioned for off season storage it really just makes sense to pickle the watermaker and then you don’t need to have any power or pumps turned on when you are away for the season.
An IMPORTANT WARNING about pickling before you begin:
You should always use the recommend pickling agent for your watermaker. Just because your dock neighbour uses X-Pickling agent doesn’t mean you can! Maybe your watermaker will be DAMAGED by X-Pickling agent and needs to use Y-agent! For example, ALL Energy Recovery pump Watermakers (like SPECTRA or SCHENKER) need to use a citric acid based agent, which they call SC1 (Storage Compound 1) OR they can use food grade and alcohol-free Propylene Glycol (PG). PG is really the best picking agent and can last the longest, but it’s hard to find in warm climates. Piston Pump Watermakers can also use PG but they primarily use Sodium or Potassium Metabisulfite, which is the same agent used to sterilize beer and wine making equipment. Using Metabisulfite on a Schenker or Spectra watermaker WILL Damaged the Pump internals!
Now, what is the Proper way to pickle?
1. Install new Prefilters:(Why: The point of pickling is to sterilize the watermaker internals and kill all the biological life. The Prefilters are where 90% of the biological life lives inside a watermaker, so by removing the old prefilters and installing new prefilters, you are removing the bulk of living creatures and giving the food grade biocide (pickling reagent) the best chance of success. Also, this makes it easier to recommission the system when you return. Just purge out the pickling reagent and you already have fresh prefilters installed and of you go.)
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Do a long fresh water flush with chlorine free fresh water:
(Why: You want to do a good fresh water flush BEFORE pulling in your pickling agent because sea water and pickling agents don’t play nice together. The salinity of the sea water can change the chemical pH and effectiveness of the pickling agent. So you want the pickling agent to mix with fresh water inside your watermaker rather than sea water. The reason for using chlorine free water is to prevent damage to the membrane(s) and this is what your carbon filter does on your water maker system (if it has one) -
Pull in the pickling agent:
Reconfigure your inlet suction side plumbing to pull in the pickling agent and make sure it flows through your prefilters. The easy way is to have a 3-way valve on the suction side of your watermaker feed pump, so in normal water making mode you are pulling in sea water from your ships through hull, but in pickling mode, you are pulling from your 5-gallon bucket. This process is covered in more detail in the Spectra manual …… I am not sure on the Schenker water makers.
(Why: You never want to pull anything through your watermaker without you prefilter in place. Because any water that flows into the watermaker flow into the RO Membranes. Solids can plug up your RO Membranes and damage your High pressure Pump.
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Brine Discharge Cycling?
(Why? Many brands of watermakers have you Recycle the picking agent that exits the brine discharge back to the bucket and run the pickling agent in a loop for 15-20 minutes. Now this is absolutely the BEST way to pickle, but speaking frankly/honestly even I’m too lazy to often do that myself and just suck in the 4-gals of pickling agent out of my 5-gallon bucket and call it good. I realize this isn’t the best way, and that by recycling the picking agent through the system for a few minutes you are doing a better job of making sure every nook and cranny of the system and RO Membrane have been thoroughly flushed by the pickling reagent. So on this issue, follow the recommendations of your specific brand of watermaker) This Rick Boren comment … I always recycle the pickling agent with the brine discharge into a bucket (this process is covered in the Spectra manual ) and my membrane is still working fine after nearly 6 years! Rick probably does the short cut because his costs of membrances is a lot cheaper than we pay!! -
You always Pickle a watermaker at Low Pressure.
Why? You don’t pickle a watermaker at it’s normal operating pressure, but rather at a lower pressure by either opening the “Depressurization Valve” on an Energy Recovery Watermaker OR by opening fully (counterclockwise) the pressure regulating valve on a Piston Pump Watermaker.)
That’s it. It’s not that difficult but you would be surprised at how many people either don’t understand the simple process OR do it completely wrong based on some “dock expert” advice. Like the one guy who told me he used the “Urea Method” of pickling his watermaker when I was troubleshooting what appeared to be fouled membranes after he returned from a 6-month layup. The Urea Method, as he called it was told to him by “a friend” saying that Urine was sterile and made for a good pickling agent if you don’t have the standard chemicals. I wish I was making this up…but it really happened. Needless to say, that client found out that Urine is also a fertilizer for Biological Growth and his price for admission was two new membranes.
Rich Boren - Cruiser Services LLC
Schenker Watermakers, Frigomar Air Conditioning
and OzeFridgeUSA Marine Refrigeration