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Idaho · 01-03-2023, 12:03

After starting with zero info about watermakers, and applying "just in time learning", I rebuilt the Little Wonder 200 system and changed its membrane.

Using the operational methods below I get about 200 TDS from salt water and 003 TDS from carbon filtered dock water.

Salt to Fresh

Set Fresh/Salt input valve to Salt. Set pressure to zero, turn on, set valves to Sample and Reject, run for 2 minutes to flush membrane of increased saline water.

Set valves to Sample and Recirculate, run for 2 minutes to reduce salt trapped in membrane.

Set valves to Sample and Reject, run for 2 minutes to remove increased saline water.

Slowly increase pressure to 800 psi, run for 3 minutes, take sample and test for TDS. I usually get 200-300 TDS.

Set valves to Tank and Reject, run until tank is full, or sun gets to low to power it.

Set valves to Sample and Reject, slowly reduce pressure to zero. Run for 2 minutes to remove high saline water.

Set valves to Sample and Recirculate, run 2 minutes to flush salt from membrane.

Set valves to Sample and Reject, run 2 minutes to remove high saline water.

Turn off. If tank isn't full, repeat entire process the next day.

Fresh to Pure

Set Fresh/Salt input valve to Fresh. Set pressure to zero, set valves to Sample and Reject, run 1 minute to clear salt water from filter and membrane.

Set valves to Sample and Recirculate, run 2 minutes to flush salt from membrane.

Set valves to Sample and Reject, run 1 minute to remove saline water.

Slowly increase pressure to 200 psi, run 1 minute and take sample. I usually get 002 to 003 TDS.

Fill jugs from sample tap for drinking, batteries, etc.

Slowly reduce pressure to zero, turn off. With fresh water in the pressure vessel, it can be left unused about 5 days.

After 5 months of using it like this, its still making 6 gph, and the membrane has not yet needed chemical cleaning.

Idaho · 02-03-2023, 03:41

Here is the reason for operating the watermaker this way.

When Fahrenheit was developing his thermometer scale, he observed that water with different amounts of dissolved solids, boiled at different temperatures. He could not get pure water and did not know how to make it.

So he settled on dissolving as much salt as possible into the water, and used that boiling temperature as the top end of his scale, 212F.

Since seawater is not fully saturated with salt, it can absorb more. After a watermaker run, the membrane is saturated with salt to a higher degree then the incoming seawater.

Thus, the procedure above washes out the excess salt from the membrane, transfers it to the incoming seawater, and dumps it overboard. Extending the life of the membrane.

When making Pure water from Fresh (declorinated with a carbon filter) the membrane is further desalinated with that procedure.

Also, by replacing all the seawater in the system with fresh, the ocean biology cannot foul the membrane and input filter for many days.

**tkeithlu** · 02-03-2023, 06:02

QUOTE: "So he settled on dissolving as much salt as possible into the water, and used that boiling temperature as the top end of his scale, 212F."

While it is not relevant the immediate question, this represents confusion. 212F converts to 100C, the boiling point of pure water under standard conditions. Fahrenheit used a brine solution as his starting point, 0F, where the solution froze, or actually the slush formed, which would be the same temperature. He used 180F between pure water freezing and pure water boiling. You can replicate his 0F by mixing rock salt and ice when making ice cream.

Idaho · 02-03-2023, 09:26

Thank you for that correction.

In this case the point is, that seawater is not fully saturated with salt, thus it can absorb salt from the membrane, and should be used for that cleaning purpose, before and after each time the watermaker is run.

**Tellie** · 04-03-2023, 06:59

Quote:

Originally Posted by Idaho

Here is the reason for operating the watermaker this way.

When Fahrenheit was developing his thermometer scale, he observed that water with different amounts of dissolved solids, boiled at different temperatures. He could not get pure water and did not know how to make it.

So he settled on dissolving as much salt as possible into the water, and used that boiling temperature as the top end of his scale, 212F.

Since seawater is not fully saturated with salt, it can absorb more. After a watermaker run, the membrane is saturated with salt to a higher degree then the incoming seawater.

Thus, the procedure above washes out the excess salt from the membrane, transfers it to the incoming seawater, and dumps it overboard. Extending the life of the membrane.

When making Pure water from Fresh (declorinated with a carbon filter) the membrane is further desalinated with that procedure.

Also, by replacing all the seawater in the system with fresh, the ocean biology cannot foul the membrane and input filter for many days.

True, but it's a bit long in the tooth way to just say, "Fresh water flush your watermaker after each use". But I did enjoy the read. Thanks.

sailorboy1 · 04-03-2023, 08:29

Quote:

Originally Posted by Tellie

True, but it's a bit long in the tooth way to just say, "Fresh water flush your watermaker after each use". But I did enjoy the read. Thanks.

Near as I have been able to determine the BEST thing you can do with your watermaker is fresh water flush it a LOT. Better to flush 5 gal than 3, it isn't "wasting" 2 gals it is making a better chance you haven't fouled the membranes. And it is better to repeat every 5 day instead of 7 for the same reason (I am currently just running mine every 5 gals just because may as well if I am going to flush it again).

I violated this and right now am only making 25 gph instead of 35 gph and it will be $500 to correct when I get back to US.

**Tellie** · 06-03-2023, 01:51

Quote:

Originally Posted by sailorboy1

Near as I have been able to determine the BEST thing you can do with your watermaker is fresh water flush it a LOT. Better to flush 5 gal than 3, it isn't "wasting" 2 gals it is making a better chance you haven't fouled the membranes. And it is better to repeat every 5 day instead of 7 for the same reason (I am currently just running mine every 5 gals just because may as well if I am going to flush it again).

I violated this and right now am only making 25 gph instead of 35 gph and it will be $500 to correct when I get back to US.

Perhaps we should look at your freshwater flush set up. You may already know this sailorboy but for others. This is one of the most overlooked initial set up procedures most installers never do and is the death of many a membrane. It is not a matter of how many gallons of fresh water you send through your system during the Freshwater Flush (FWF). First a quick understanding of the FWF. Most watermakers main feed pump can demand far more gpm than your house pressure pump can provide. If this occurs, then it is very likely that your watermaker will be looking for the missing amount of water and draw this extra amount up through the intake thru hull thus adding salt water to the FWF mix and never really properly flushing your system. Many times a watermakers feed pump motor speed must be adjusted to make this match by slowing them down some and reducing the gpm input demand. The proper way to determine if you have performed a proper flush is to measure the brine discharge water right after the FWF is complete. This water must be below 1,000PPMs. If it is too high say ex: 1,700PPMs then try to flush for another minute and take another reading, If the PPMs start come down each extra minute then you are on the right path. Keep doing this minute increase until you are below 1,000PPMs and once you get there, you'll know how long you FWF your system for. Of course, the opposite is true. If you can get your PPMs below 1,000 in a shorter time frame then you shorten the flush time. If you do not balance the input from the house pressure pump to your watermakers demand and draw in even a slight miniscule amount of salt water, you could flush your watermaker with 200gal from your freshwater tanks and still not have a proper flush and bio-foul your membrane/s.

Idaho · 06-03-2023, 03:43

"Most watermakers main feed pump can demand far more gpm than your house pressure pump can provide."

The obvious solution is to not feed the watermaker fresh water via the house pressure pump.

Feed it directly from the tank, preferably from a lower drain outlet on the tank.

**Tellie** · 06-03-2023, 05:16

Quote:

Originally Posted by Idaho

"Most watermakers main feed pump can demand far more gpm than your house pressure pump can provide."

The obvious solution is to not feed the watermaker fresh water via the house pressure pump.

Feed it directly from the tank, preferably from a lower drain outlet on the tank.

You need to be careful here. Not feeding many watermakers a positive input flow and pressure from the house FW pump can damage many systems. Gravity feed is also not always possible when many freshwater tanks are located below the watermaker in bilge areas etc. Most manufacturers will instruct you to tap into the boats cold water line.