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TDS creeping up

Discussion in 'Watermakers' started by Pascal, Jul 21, 2020.

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  1. Pascal

    Pascal Senior Member

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    I think I know the answer but just in case....

    aquawhisper 1400, 4 years old / 1500 hours. membranes... TDS has been creeping up at a set 800PSI and 70GPH product flow. Used to show 2 to 3 green bats now it s full green and sometimes 1 or 2 orange bars.

    seems to me the membranes are done.

    am I wrong ?
  2. Capt J

    Capt J Senior Member

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    How are your pre-filters? Try changing those first if they're old. But most likely it's membranes. 1400 gpd is 60 gph +/-, try 700 psi and see what the salinity is.
  3. Capt Ralph

    Capt Ralph Senior Member

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    Any snake oils to clean the membranes? Back wash program available?
    Like Skippy J suggested, If not done already, Clear all the cheaper pre-filters first.
    Those were used membranes when you took over the boat, no telling of any proper use or abuse.
  4. Capt Ralph

    Capt Ralph Senior Member

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    One of our ROs is an old Rich system. Single long membrane for 300GPD.
    Horizon has a cleaner that I use for this system and it comes back to life. Picked up from BOW on hy84 in Liqurdale years ago.
    Sadly, The ole Rich system will be replaced this fall. Have an old 3 membrane SR that will fit rite in.
  5. Pascal

    Pascal Senior Member

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    I ve tried adjusting the pressure to various levels with no difference. Prefilter is clean, I changed it a few days ago made no difference
  6. Capt Ralph

    Capt Ralph Senior Member

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    Product flow gauge/sensor error? You may be making water and can't prove it.
  7. olderboater

    olderboater Senior Member

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    Have you been regularly cleaning the membrane? If you haven't, I'd try cleaning it before giving up on it. If not properly maintained, 4 years can be the limit, but we get far longer out of our membranes and we do have Sea Recovery. We also have commercial pre-filters and regularly do the fresh water flush. Normal maintenance includes cleaning every two years and normal life is quoted at 5 years. We've exceeded that and still doing fine.
  8. Pascal

    Pascal Senior Member

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    Commercial filters and weekly flush yes. Cleaning no. I had asked the guy who replaced the membranes 4 years he said not necessary. Will probably try that when we get back. Thing is when we re here in the Exumas with a full house we run it up to 12 hours a day....
  9. d_meister

    d_meister Senior Member

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    When RO watermakers first became available for recreational users, the instructions said to dial it up to 800 lbs. As the sea water became warmer, the product water volume increased and we thought it was a bonus.
    At another point in product development, the instructions said to dial the pressure to the point where production reached the specced output, irrespective of back pressure (up to a point). Anyway, a little research revealed that TDS increases when specified output is exceeded. Now, some watermakers have back-pressure regulators preset and lock-nutted, requiring two wrenches to adjust.
    All in all, it seems that your membranes are near the end of their useful life. It might be interesting to see if lowering the output further below spec would decrease Total Dissolved Solids.
    Despite the mystique of "Reverse Osmosis", the system is no more than a series of filters, with the membrane filtering at the near molecular level.
    [​IMG]
  10. Capt Ralph

    Capt Ralph Senior Member

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    You just have the one system?
  11. olderboater

    olderboater Senior Member

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    They recommend cleaning every two years. Here is a link to the owner's manual, page 51 is the cleaning process. There are different cleaners for different things. The only thing they say cannot be cleaned is chemical damage. The most common chemical problem is petroleum. That's why we have a an oil/water separator but where you use it most, probably not an issue.

    https://www.searecovery.com.au/downloads/B651950001 MANUAL-AQUA-WHISPER-PRO-Rev 03_15.pdf
  12. Pascal

    Pascal Senior Member

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    Thanks for the info. I ll try setting a lower pressure again

    Yeah only one on board :(
  13. Pascal

    Pascal Senior Member

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    I read the Manual again yesterday. I guess the guy who told me cleaning would not help just wanted to sell us new membranes... I stopped using him soon after that ...
  14. olderboater

    olderboater Senior Member

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    My understanding is that many membranes can't be cleaned but Sea Recovery is designed to be cleaned periodically.
  15. d_meister

    d_meister Senior Member

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    Cleaning and storage processes have also changed over the years, and mostly after the routine fitting of fresh water flush. Back in the day, the process was to get a 10 gal tub and mix in first a powdered alkali and recirculate the solution through the system for a period of time. The alkali was for removing organics. Following that, the same procedure was done with an acid to dissolve minerals. Then, if the equipment was to be unused for a period of time, a storage solution was drawn into the system. Later, the two cleaners were pre-packaged in prefilter substitute cartridges that did the same job, easier, and without the 10 gallon tub business. At least Village Marine Tech has that.
    Fresh water flush is pretty much all that is necessary during the lifetime of the membranes. That's when staged prefiltering is done, like plankton screen, 20 micron, and then 5 micron If the membranes require cleaning, the tell is that the production decreases at the same pressure, or more pressure is required to achieve the specified output.
    Bear in mind that there is a great deal of an abrasive version of water flowing across plastics. It's pretty much a race to the finish of a membrane getting clogged or worn out, these days. Fortunately, with fresh water flush, it's a good long time.
    Incidentally, membranes are mostly all made the same way and can be cleaned the same way. There are membranes made for different purposes like purifying fresh water to a certain level, like removing metals and bacteria. Interestingly, virus survive the punishing low pressure to high pressure to low pressure transition, which is why UV sterilizers are desirable on RO systems.
  16. Pascal

    Pascal Senior Member

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    I ve tried adjusting the pressure down... no change in TDS. From 800 to 700 PSi product flow goes from 70 to 60 but TDS remained constant at full green or one yellow.

    now after 90 minute running TDS is jumping every seconds from 1 green bar to full green bars. Wonder if the TDS probe isn’t the culprit.

    glad i can zoom in the ER cam on the watermaker :)
  17. d_meister

    d_meister Senior Member

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    It can be the probe, although they tend to be all or nothing. You can pull it and examine it closely. If it's the dual pin type, those pins are gold plated and can erode. I had one once that had some kind of black particles that almost formed a bridge from one sensor probe to the other, causing intermittent water quality conditions. It was finer than a human hair and I don't know how it stayed in place when I removed the sensor.
    Apparently you're not at the point where it shuts down production, so you could possibly hang on until you go back. Even at the limit of the acceptable scale, it's doubtful that it would harm anyone. It almost certainly wouldn't taste salty.
  18. Capt Ralph

    Capt Ralph Senior Member

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    This was a suspect. Can you get one in with the stabilizer pump flight?
  19. Pascal

    Pascal Senior Member

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    We Re heading back next week, last guests leaving Sunday so I m not going to mess with it. We can always go to Staniel and fill up if needed.
  20. Capt J

    Capt J Senior Member

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    See if you can find someone (megayacht or large yacht usually) that has a salinity meter. They're usually a $50-60 tool, so most will have one in the engine room and an instant check. OR, bottle some of your water and take to a place once you get home.