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post #1 of 98 Old 12-18-2017 Thread Starter
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watermaker membrane cleaning?

Hi guys getting ready to buy a watermaker, but I'm going to be cruising fresh water for one more year before heading off to the ocean.
I have read that you can filter fresh water with a R/O as long at you decrease the pressure to get the flow you would get when running in salt water. ie if you get 15 gallons per hour of drinking water from salt water, then reduce the pressure till you get 15 gph of drinking water from fresh water. Seems simple enough. But I have also read that in fresh water the filters may become dirty (if that's the right word) and you would need to replace them more often.

So my daughter is a chemical engineer and worked at the plant that made the filters so I asked her she told me that you could run bleach thru them to kill any growth, but she didn't know how much fresh water would be needed to get the bleach out.

So that lead me to YouTube you can learn everything from YouTube right?

Seems like you can clean the membranes, but looking at the boating forums it doesn't seem like anyone does clean their membranes.

So for those in the know can you clean the membranes?

next related question...
pickling your filters I have seen all kinds of mixtures people use, again my daughter told me plain old vinegar would do the trick.
I'm up in the great white north so when I would need to pickle the membranes would be for the winter, I don't think vinegar freezes but I don't know.

So you northerners how do you winterize your watermakers

thanks
Bob
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post #2 of 98 Old 12-18-2017
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Re: watermaker membrane cleaning?

First of all, stop talking to your daughter about RO membranes. I'm sure she means well, but her advice above is very bad and would ruin the membrane.

Second, please clarify whether you are talking about the filters used before the RO membrane when you discuss filters becoming dirty and needing cleaning, or the RO membrane itself.

I didn't watch the video, so don't know what they say there. However, it seems like they are talking about industrial plants, which are much different in operation than a cruising boat system.

Here is a typical general watermaker component setup: Raw water intake > strainer > filter > watermaker pump > RO membrane > Fresh water tank.

So there are filters and a membrane involved. The membrane is a type of filter, but not really discussed as such in describing components.

Bleach will almost immediately kill a RO membrane. Even a little bit at very low concentrations is harmful. Vinegar won't kill the membrane, but it won't be helpful. Since it freezes at 28F, it would kill the membrane in the winter. Neither should be used in a watermaker system for any purpose.

Fresh water won't foul a RO membrane any more/quicker than salt water. In fact, I suspect less fouling would occur. Fresh water might foul the filters faster if it has a lot more stuff in it than salt water. Often times, this is the case with fresh lake water containing algae, etc.

Cleaning filters is easy, and replacing them as needed is cheap. Carrying around a bunch of filter cartridges is normal for a cruising boat.

Cleaning RO membranes is rare, and few people carry around spare membranes. As long as the membrane is flushed with clean fresh water after each use, fouling doesn't occur much, and neither does calcification.

If the RO membrane does need to be cleaned, one would use sodium hydroxide for biofouling and citric acid for chemical fouling. Again, this is very rarely necessary.

To store RO membranes in freezing weather, just store the entire system in -100F glycol antifreeze like used in protecting boat/rv fresh water systems. This both preserves the membrane and keeps it from freezing. Alternately, you could remove the membrane, put it in a bag with a glycol solution and take it home.

But the very best way to keep a membrane from freezing is to keep the boat containing it in a nice, sunny, warm climate.

Mark

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Re: watermaker membrane cleaning?

My understanding is that even the tiniest bit of bleach can damage the RO membranes permanently. Perhaps your daughter was speaking about the prefilters.
I would suggest you contact Rich at [email protected] with any questions you might have. He is extremely knowledgeable and helpful about watermakers and their parts and will not try to sell you anything, though I have found him a great source for parts when needed.

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post #4 of 98 Old 12-18-2017 Thread Starter
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Re: watermaker membrane cleaning?

Raw water intake > strainer > filter > watermaker pump > RO membrane > Fresh water tank

I knew the pieces of the system I have even looked at building my own, doesn't seem very hard.

I like where you said the best way to winterize a boat is to have it in a warm place!!! my plans exactly!!!

would of thought the antifreeze wouldn't of been good for the system good old pink stuff.

my daughter said that what they did with the filters they were using, but those filters weren't a membrane even though that's the plant she worked at.

Cruise RO is top of my list if I end up buying new vs. used or building my own system.
Bob
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Re: watermaker membrane cleaning?

Quote:
Originally Posted by snokid View Post
Raw water intake > strainer > filter > watermaker pump > RO membrane > Fresh water tank

I knew the pieces of the system I have even looked at building my own, doesn't seem very hard.

I like where you said the best way to winterize a boat is to have it in a warm place!!! my plans exactly!!!

would of thought the antifreeze wouldn't of been good for the system good old pink stuff.

my daughter said that what they did with the filters they were using, but those filters weren't a membrane even though that's the plant she worked at.

Cruise RO is top of my list if I end up buying new vs. used or building my own system.
Bob
I didn't mean to offend with simplicity - it just wasn't clear to me whether you were talking about the filters or the membrane at various points.

It isn't difficult to build your own system, but it is time-consuming searching for good deals on parts, and fiddly getting all of the small bits and bobs together. I was going to do so, but then realized that it would take me months of searching for deals on the pump, motor, valves, and housings just to save $300-500 over a complete system. If I just ordered the parts retail, I wouldn't save any money at all.

The pink stuff isn't very good for pickling because that is the -50F antifreeze. If I remember correctly, the -100F antifreeze is blue. But then, I'm trying very hard to forget everything I know about living in Michigan winters.

We have a CruiseRO system and it is very good - it just pumps out water continually without complaining. However, it is an AC-powered system, so that requires a generator. If you want a DC-powered system, then CruiseRO would not be a good choice. The only good choice there is an energy-recovery system like Spectra (there aren't many others like this).

If you build your own DC powered system, then you will be running a generator anyway to make water, because they are power hogs that don't perform well unless the batteries are at charging voltage when running. We cruised for several years with a DC system and found we were running the generator most of the time anyway, so just got an AC system instead. The advantage is that we now make 30gal/hr instead of 6.

Mark

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Re: watermaker membrane cleaning?

Quote:
Originally Posted by snokid View Post
Cruise RO is top of my list if I end up buying new vs. used or building my own system.
Bob
Rich helped us build our own, plenty of good advice. As I said, no pressure to buy anything, but he often has some of the parts at a good price that are harder to source.
I installed a HM Digital, Inc PPM meter in the system instead of using a portable one. Battery operated (lasted 6 years & replaceable), so no wiring beyond the sensor, which goes right behind the panel. I also used Pex fittings and Pex tubing after the prefilters, for all but the high pressure lines; really simple and color coded.
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Re: watermaker membrane cleaning?

colemj just got to give my wife time to retire, or change her mind and get retired sooner!!! I keep telling her you can't take the money to the grave!!!! November 1st 2019 is when she want's to wait till. She's a teacher so she has the whole summer off so the summer after next we start our journey get as far south as we can and she flies back to work sept, oct. then back to the boat and warmth!!!

We are in a 40' mono cats like your sure look nice I really like the leopard 43's don't know might end up with one, really not sure yet.

Having refit most of the boat this last summer, in what free time I had, I was care giver for my wife's father who has since been placed in a home. So my free time was very limited, only have to finish the wiring, finish the davit's, build a dodger/bimmini, install the windlass, and get and install a watermaker and we are ready!!! Most of that I can have done before schools out for the summer this spring.

Then we are going to live on the hook as much as possible this summer,(north channel) kind of silly but we are still paying for a slip anyways. But since we are going to spend as much time on the hook as we can I figured I should be looking at either increasing our fresh water storage or installing a water maker now. That's what got me researching watermakers and fresh water usage.



capta, thank you I will give Rich a email. This is really the start of my research. I know the system is pretty much a thru hull, a strainer, a prefilter, a pump, the membranes, couple of gauges and valves, and another thru hull for the brine. The little bit of research seems to lead to bigger is better, but with a mono space is more limited, but really it's just the membranes that get bigger so where can I stuff them? LOL I know I don't want a system that only can make 1.5 gallons per hour for sure. thinking in the 10-20 gallons per hour seems much more suitable. I have solar but I know that won't keep up with a bigger pump if I go with 12v could run the motor when making water though. going with cruise RO I would also have to get a little Honda to power it, then that means gas can's on the lifelines...

lol choices!!!
Bob
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post #8 of 98 Old 12-19-2017
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Re: watermaker membrane cleaning?

The Spectra 150 gives you 6 gallons per hour with a consumption of 9 AH. There isn't a watermaker more efficient than this. Easy to run off solar as many do.

Brian
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Re: watermaker membrane cleaning?

Recent Practical Sailor article on 12V units

https://www.practical-sailor.com/iss...es/4384-1.html
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Re: watermaker membrane cleaning?

Quote:
Originally Posted by john61ct View Post
Recent Practical Sailor article on 12V units

https://www.practical-sailor.com/iss...es/4384-1.html
Recent? From last century. A lot has changed since 1998.

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