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Thread: Water Maker

  1. #11
    Join Date
    May 2001
    Location
    London/Antibes
    Posts
    21,385

    Default Re: Water Maker

    Quote Originally Posted by Magnum View Post
    I'm with jfm on the water maker maintenance issue. We don't pickle our membranes and never have. I do auto flush every 7 days though which uses about 40L of water on our Sea Recovery unit.

    jfm, have you ever considered going to the next stage of water purification by fitting a Spot Zero system? You can feed it with dock or water maker water and the results are incredible. No need to dry the boat by hand, just let it drip dry for a spot free finish.
    Mine is SeaRecovery too, with 7 day auto backflush, and it has been brilliant. Both the smaller 140lph unit I had before and now this 280lph unit. Main issue is to change the carbon filter for the backflush supply often, else the membrane is damaged by chlorine if it back flushes using dockwater - the carbon takes out the chlorine.

    I've thought about spot zero but am not convinced

    The water makerwater is so good that it already does perfect washdowns, so I don't see the need to re-process that water.

    Dockwater however would be nice to process through RO. Those ion-exchange resins that you see lots of people using are rubbish so a reverse osmosis system like SpotZero is the right method, but the problem is that the flow rates and rejection rates from these spot zero systems just don't cut it in my book.

    Typically you might come into port low on water in the evening, or you're going out for the day and notice that your water is low, both of which can happen if you haven't or aren't going to spend many hours underway running a noisy watermaker. In these situations you don't want a system that only does 300-400 lph else you'll be waiting too long. You could of course have say 2x 1000 litre tanks on a 24m boat, and take 1000 litres of dockwater in 15 mins into tank #1 then go to sea and let the system take 3 hours to process it and put it into tank #2, but you generally wont have the space to devote to two 1000 litre tanks.

    So while I like the concept I don't see that it really works, at least in my use of the boat, as a good purifier of dockwater, and I feel it is pointless to re-process watermaker water when it is so good to begin with.

    Then there is rejection rate: RO machines reject some of the water they draw as the "brine" With a normal watermaker 80-90% of the seawater sucked in is rejected right back to the sea but that doesn't matter because you have unlimited seawater obviously. But when you're purifying your already made water, and these units reject 1/3 of their throughput as the "brine", you have a big negative. If you tag a spot zero onto your 300lph watermaker you create a 200lph watermaking system, erk. So on top of the €10k cost of the spot zero system you therefore have to add the cost, noise and extra space of a 50% bigger watermaker. Just doesn't make sense to me. I find the marketing a bit hyped and lacking in real analysis and data too
    Last edited by jfm; 15-11-17 at 19:56.

  2. #12
    Join Date
    Jan 2004
    Location
    Jersey
    Posts
    2,699

    Default Re: Water Maker

    Agreed jfm, the main application for spot zero is dockwater.

    Low water upon arrival isn't really an issue as we always run the water maker at anchor or under way. Worst case scenario would be 75% full.

    We have specified a 348l/h water maker and 473l/h spot zero system to fill new Magnum's 1350l water tank, so from dock water we get 1/3 tank in an hour.

  3. #13
    Join Date
    Mar 2002
    Posts
    14,361

    Default Re: Water Maker

    Quote Originally Posted by jfm View Post
    Dockwater however would be nice to process through RO. Those ion-exchange resins that you see lots of people using are rubbish so a reverse osmosis system like SpotZero is the right method
    I fully agree that it's pointless to further process the water produced by a watermaker with a RO system, which can instead make sense for loading dockwater.
    Otoh, I can't understand why you dismiss the alternative of ion exchange water softeners, for that purpose.
    As a premise, I'm not interested in a watermaker, because I don't need it for my typical boat usage. But since I spend a LOT of time onboard, I am indeed interested in having decent fresh water - both from direct dock supply, and when loading the tank before going out.
    So, I thought to discuss the alternative of a full flagged RO purifier vs. a ion exchange water softener with an old colleague and friend who forgot more about all this stuff than most chemist will ever know.
    And his only question was: are you going to drink the processed water?
    I told him that I am not, because I also use - as you do - water for everything but drinking.
    On that basis, his suggestion was to avoid wasting money for a RO equipment, because a much cheaper, simpler and more efficient water softener (plus a good filter) would have been for all intent and purposes equally effective.
    Btw, this matches nicely my experience at home, where I have a large water softener+filter, plus a small RO purifier in the kitchen, specifically meant to supply drinking water. And while the difference between the original hard water and the softened one is like day and night (much softer hairs, no marks when rinsing shower walls, no deposits on taps, etc.), there is absolutely no perceivable difference in these respects between softened-only and softened+purified water.

  4. #14
    Join Date
    Jun 2001
    Location
    Guernsey, Channel Islands
    Posts
    3,059

    Default Re: Water Maker

    Thanks for all the replies. Really interesting.

    May I ask a further qn? Do you have separate water tanks. E.g., one for water maker water, the other for dock water?
    These are the voyages of Play d'eau....www.playdeau.com

  5. #15
    Join Date
    Jan 2004
    Location
    Jersey
    Posts
    2,699

    Default Re: Water Maker

    Quote Originally Posted by Piers View Post
    Thanks for all the replies. Really interesting.

    May I ask a further qn? Do you have separate water tanks. E.g., one for water maker water, the other for dock water?
    No we don't, hence the plan to run dock water through the spot zero system.

  6. #16
    Join Date
    Sep 2016
    Posts
    2,487

    Default Re: Water Maker

    I take bottled water aboard for drinking. Only a tiny percentage of water is actually consumed so it’s economical to take a six pack of 1.5 litre bottles which should be enough for a couple for a weekend

  7. #17
    Join Date
    May 2001
    Location
    London/Antibes
    Posts
    21,385

    Default Re: Water Maker

    Quote Originally Posted by Piers View Post
    Thanks for all the replies. Really interesting.

    May I ask a further qn? Do you have separate water tanks. E.g., one for water maker water, the other for dock water?
    My boat is plumbed to do this:

    1. two tanks, connected by a linking pipe that can be shut with a valve,
    2. Valves that allow the pump to draw from either or both tanks
    3. Watermaker feeds to one tank only
    4. Each tank can be individually dock filled
    5. Separate contents gauge for each tank

    But I never use this facility. I leave the valve open in the balancing pipe that connects the two tanks, and run the system as one virtual tank.

    I have not dual-plumbed the boat, so I could not have watermaker water feeding some taps/showers/hosepipes, and town water feeding others. I thought about it and didn't see the point. But I could, within 30 seconds of valve operation in the crew cabin, without removing any panels or using any tools, switch from whole boat being fed by w/maker water, to whole boat being fed by town water. And if you could be bothered (I couldn't) you could do all this with electric valves (3, I think) and switches on the dashboard.

  8. #18
    Join Date
    Apr 2013
    Posts
    158

    Default Re: Water Maker

    Having just re-read BartW great thread on his bladder tank project it made me curious why people don't consider this for extra water capacity. Our tanks at 450l are typically fine for 1 or 2 nights at anchor with sensible consumption. For the few occasions each year when we maybe out for 3-5 nights the idea of doubling that capacity with bladder tanks seems quite compelling. Apart from the installation logistics is there any reason why this is not sensible alternative for occasional use ?

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