Aaron's blog

Seawater Pro watermaker install on our Hunter 376 sailboat

By aaron.axvig, Mon, 03/09/2020 - 09:33
Watermaker system overview

In this post I will document the Seawater Pro watermaker that we installed one year ago.  It currently makes 15 gallons per hour here in the Bahamas at about 850 PSI membrane pressure while consuming about 850 watts.

I ordered and installed the system in March 2019, probably total installed cost was about $3,100 and a solid week+ of learning, working and running to hardware stores.

  • $2,575 to Seawater Pro.  It looks like this $2395 item currently in their store is basically what I got.  I would really recommend getting the "remote control" version which is basically a pretty panel to put the controls and gauges in, but it is $400 more and you have to draw the line somewhere.
    • Base system price was $1,595
    • $699 for the DC motor and brass pump upgrade
    • $39 for the SW30-2540 membrane (an upgrade? I see they retail for more like $200 online?)
    • $80 shipping and some tax were the remainder
  • Additional costs rough estimates (one year ago by memory!)
    • $250 for plumbing odds and ends not included "in the box"
      • Boost pump is far from high pressure pump
      • Had to split air conditioner sea water intake (do not run AC and watermaker at the same time)
      • New dump overboard through the hull for salt water output
      • New input into top of water tank
      • Valves to direct product water overboard or into water tank
      • Misc. to get house water to the system for flushing
    • $250 for wiring
      • About 30 feet of 2AWG marine wire
      • Circuit breakers
      • Compression lugs, heat shrink, looming, etc.

What the operating process looks like, plus notes about a few steps that we skip:

  1. Ensure needle valve is open (unrestricted).
  2. Ensure product water valves are set to flow overboard and put that dump hose out the v-berth hatch. (usually skip this and just dump straight into water tank...20 seconds of 2,000 TDS water is quickly diluted by the following hour or two of usually 100 TDS water)
  3. Turn on salt water boost pump.
  4. Verify that the pressure gauge before the salt water high pressure pump shows higher than 0 PSI (usually skip this, depends on cleanliness of sea water in the area).
  5. Turn on salt water high pressure pump.
  6. Tighten needle valve over about 20 seconds to bring pressure to 750-850 PSI, observing GPH meter rise to 15 GPH (or more, or less).
  7. Turn on the TDS monitor and observe it drop from around 2,000 to under 200.
  8. Open product water valve to water tank, and then close the one that dumps overboard. (usually skip this)
  9. Put away overboard dump hose. (usually we don't dump any water so skip this)
  10. Run for a long time, typically one to two hours.  Monitor both low pressure and high pressure gauges every 20-30 minutes, and also listen to the sounds of the system for interesting changes.
  11. Loosen the needle valve slowly over 20 seconds to bring high pressure to 0 PSI.
  12. Turn off high pressure pump.
  13. Turn off boost pump.
  14. Flush system with fresh water. This ideally would mean doing something with the garden sprinkler timer but I haven't gotten that to work so I flip open a valve under the settee. (usually we skip this)

So basically we are doing two "naughty" things.  We don't dump the initial product water overboard, but the math on dilution is quite convincing to me that it doesn't really matter, the water tastes fine, and we are generally healthy.  And we don't flush with fresh water after running, but the system performance does not seem significantly degraded.  Perhaps we will need to replace the $200(?) membrane earlier than the 5-10 years that people normally get out of them.

Our system has a 12V high pressure motor.  At operating pressure this alone seems to draw about 800 watts (65A at 12V), with the boost pump drawing the other 50 watts.  For our 4x 100Ah 12V lithium iron phosphate (BattleBorn) battery bank this is no problem.  It may not work so well on smallish lead-acid battery banks, in which case using a generator and 120V AC pump would be wiser.  If we run the generator our battery charger can put out about 90A so it can charge the battery a little in addition to keeping up with the watermaker draw.  But mostly we get enough solar from our 1100 watts of panels to keep up with the fairly liberal demands of the two of us.

Boat water systems diagram
The complete water system diagram on our boat.  The watermaker is half of it!
New input into water tank
The new fixture that I added on top of the water tank for product water to drop in.
Boost pump breaker
The breaker for the salt water boost pump.  Turn this on first!
Seawater plumbing under the floorboards
Under the floorboards with dog hair!  The seacock has the yellow handle on it, which flows to the strainer on the left.  Above that, a Y-valve goes to both the 120V AC pump for the air conditioner (top) and the 12V pump which boosts seawater to the watermaker's high pressure pump.  The "Watermaker Supply" breaker on the boat's breaker panel turns this 12V pump on.  Someday when I need to pickle the system I will have to modify this plumbing to provide a way to suck the pickling solution into the system.
Breaker under nav station
This breaker is under the nav station, like exactly where it could be bumped by a knee.  I think the labels explain enough for this picture!
Pump nameplate
Here is the nameplate on the high pressure pump motor.
Main watermaker parts overview
This is an overview of all the main watermaker parts on a shelf that I built in the v-berth closet.  If the photo was oriented correctly, from left to right: TDS and GPH gauges, coiled up hose for dumping product water out the v-berth hatch, high pressure pump, needle valve (silver handle), high pressure gauge peeking out under the shelf, fresh water flush timer and one-way valves, and sea water filtration.  The glowing thing in the back is daylight coming in through the through hull.
Seawater filtration
Seawater filtration!  Seawater leaves the boost pump and travels under the couch around the table, under the v-berth sink, through the space where the water tank is, and finally comes in through the left one-way valve.  Fresh water for flushing leaves the house pressure pump (I installed the carbon filter that came with the system so that it filters all house water...to remove any chlorine which would damage the membrane) and travels under the v-berth sink, through the space where the water tank is, and finally comes in through the timer and right one-way valve.  Then ideally a 20 micron filter and 5 micron filter.  I believe Seawater Pro says that the actual sizes don't matter much.  I just run 20 micron filters in both.  In dirty water they plug up pretty fast (3-5 hours?) so I have been known to just run one out of frustration...lasts longer then.  Not optimal for system life I guess.  In the Bahamas we have run with both for maybe 30 hours now and they are still quite clean.  I guess I didn't need the 20 filters that I stashed under the bed!  When the pressure on this gauge drops to zero it means the boost pump isn't able to pump enough water through the filters because they are dirty, so soon your high pressure pump will start making upset noises as it draws in air or a vacuum.  Not good for that, should be avoided.
High pressure pump close-up
A closeup of the high pressure components.  The high pressure pump has to be oriented with the yellow fill cap/dipstick facing up.  The pump can be rotated to any 90-degree position on the motor so if you need to bolt the motor to the wall that is fine.  Mine is bolted to the shelf, which is built out of PVC boards from Lowe's/Home Depot.  The big high pressure line coming out of the pump runs to the far end of the membrane housing which is under the v-berth bed.  And then you can see the "near" end of the membrane enclosure in this photo.  It has two connections.  The first is high pressure to the gauge you see here, this is what we run at 750-850 PSI.  Then the needle valve which lets some water past but still holds the pressure high.  Then that pipe (which mysteriously became dirty after a few hours of running) goes overboard through the hull in the back of the cabinet.  My positioning of these things is not ideal and I can't quite tighten one of the connections enough and still have them fit it the "custom" hole I made in the shelf, so I get a very flow drip in this part of the high pressure system.  The second connection is the product water output.
Plumbing for directing product water
This is the plumbing for handling the product water.  First it hits the sensor for the TDS monitor and then goes to the GPH meter.  From there I can choose to direct the water to a hose that I can put overboard out the v-berth hatch, or send it to the water tank.  A Y-valve would be ideal for this but I couldn't find the appropriate one in-stock at the time.

That's it!


The Three-Body Problem by Liu Cixin

By aaron.axvig, Sat, 03/07/2020 - 13:24
Date completed
4 years 2 months ago

Overall good.  I read reviews for the sequel and some of them said that reading this is a necessary slog and the sequel is the big payoff.  One of the best sci-fi books of all time I guess.  I do plan to read it.

This itself is still a good book though.  I found it hard to keep track of the characters, I think because they all have Chinese names.  Maybe I don't have anything to visualize for names that I am unfamiliar with, or maybe my brain just isn't wired to track those "words" as characters.  Otherwise the Chinese setting and cultural influences are interesting.

I actually should reread the book as I read a lot of it while falling asleep.  Might help rewire my brain for the names too!

Completion status

The Stone Sky by N. K. Jemisin

By aaron.axvig, Tue, 02/25/2020 - 18:05
Date completed
4 years 2 months ago

Much more going on in this third book, which I really liked.  More big events and especially more explanations of the history of the world.

It reminds me of a college class where the lectures were pretty boring but then one day the lecture involved some real-world uses for the stuff we were studying (how some industrial plants use huge inductors to fix their power factor and decrease their electricity bill).  I told the professor that I really enjoyed the lecture that day, which he probably already knew because I wasn't nodding off in the back of class...shame.  And he responded that you have to lay a little theoretical foundation so that you can understand the exciting real-world stuff.  I see a similar parallel here where the first two books were good enough but sometime frustrating, and this one was the big payoff.

After finishing the second book I read some news articles about the "puppies" factions attempting to influence the Hugo voting around the times that these three novels were coming out.  Definitely an unfortunate series of events!

I found myself questioning the wisdom of letting the Hugo winners list heavily influence my selection of reading...maybe populism isn't necessarily the best indicator of quality (to be clear, nothing against this trilogy in particular).  But on the flip side, I can remember having sympathized with criticisms of other awards (Oscars or similar?) that are selected by industry members, thinking that a group of insiders like that may not be very representative of my interests as a consumer.

Completion status

The Obelisk Gate by N. K. Jemisin

By aaron.axvig, Mon, 02/24/2020 - 09:34
Date completed
4 years 3 months ago

The second novel in this trilogy.  Overall a good read.  After the hint about the moon at the end of the first novel, I expected more to happen with that in this novel.  Instead it is just a build up (explanation) of the mechanisms that will presumably be used to manipulate the moon in the third novel.  And those mechanisms are so tediously explained, in such an "emotional" way that it is really a challenge for me to read.  Unbelievably, this second novel also ends with basically the same cliffhanger about the moon.

I say so much negative about these books, probably because I have such high expectations.  I chose to read them only because they were award winners.

Completion status

The Fifth Season by N.K. Jemisin

By aaron.axvig, Sat, 02/22/2020 - 11:09
Date completed
4 years 3 months ago

This was a pretty solid read, interesting story line and good world-building.  The writing style was not my favorite with so many paragraphs consisting of one short quip by the character and then a few sentences of the character's thoughts adding further context.  Sometimes it seemed like a really tedious way of revealing the "world" to the reader.

I started out thinking that the book probably won so many awards on a sort of "social justice" basis.  It seemed like a passably strong story, but I speculated internally that it might have been taken to award-worthiness by virtue of the strong female leads and non "white male" author.  These were unnecessary bitter thoughts and I left them behind as I got further into the book, please forgive me.  I still regard it as interesting that this book is different than so much (older, male-centric) sci-fi, containing homo, trans, and three-way relationships.  And the book is probably good enough to win awards without standing on a pedestal of social justice feel-goods.

Completion status

The Greatest Generation Speaks by Tom Brokaw

By aaron.axvig, Wed, 02/19/2020 - 21:30
Date completed
4 years 3 months ago

The writings compiled in this book do an excellent job at describing the mostly negative impacts that WWII had on its contributors, certainly making me feel like I have it pretty easy (I do!).  It did get pretty repetitive and is not what I would describe as a page turner past about halfway.  I closed it up with about 20 pages left to go, not that it was bad but just that I didn't feel that I had anything to gain by reading the last 20 pages (nor the previous 50-100 pages).

Completion status

Starship Troopers by Robert A. Heinlein

By aaron.axvig, Wed, 02/19/2020 - 21:24
Date completed
4 years 3 months ago

I haven't watched this movie for 10 or 15 years but I still found myself trying to remember it for comparison.  I'm not sure there is that much similarity!  I suppose the majority of the content of the book is not suitable for the movie screen.

I did enjoy the philosophical parts, there were some interesting ideas.  For example, the discussions of value, who is qualified to vote, etc.

Completion status


By aaron.axvig, Sun, 02/09/2020 - 15:21
Achikaps screenshot
Date completed

I found this game on the No Bullshit Games page, which lists games that don't have IAPs or ads.  So generally they cost a couple bucks, and I believe this one did.

I really like the mechanics of this game.  Little agents move around your system of facilities automatically performing tasks.  It reminds me of the World/Kingdom of Keflings which I played nigh on a decade ago.  Setting up automated systems like this is one of my favorite game mechanics.

I don't like that the campaign levels are so short.  It seems like I could get more enjoyment out of the effort I put into setting everything up.  Actually these short levels would be OK for a few tutorial levels, maybe even 10 learning levels.  But it keeps going, and with seemingly random new things mixed in.  I have passed level 27 in the campaign and it keeps throwing in new concepts that are only used for one or two levels.  By now I am maybe four hours into the game and I am tired of learning one-off things.

It would help a lot of the buildings and/or resources were intuitively named.  Gumballs are made in a laboratory?  How am I supposed to remember that?  Maybe it should be called...a gumball factory!

At this point I don't really feel like completing the campaign.

Completion status
Digital platform


By aaron.axvig, Sat, 02/01/2020 - 15:41
UnCiv screenshot
Date completed

I found this clone of Civilization (the fifth release I believe?) on the F-Droid app store.  I played through on the apparently pretty easy settings that were mostly default and got a science victory on my second playthrough.  On my first playthrough I reached 100 turns and got a message from the developer saying something like "I'm sure by now you've noticed that the game is incomplete" and just sort of put the game aside for a week or two until I decided to try it again.  Maybe the AI isn't finished as I was never attacked, or maybe it was just on that easy of a difficulty.

Overall the game played quite well.  The graphics were occasionally a little difficult for me to figure out but got easier as I got more experienced.  There is a lot going on!

It was fun to build out a big civilization and I could see myself doing it again in a month or two.

Completion status
Digital platform

A week on South Bimini

By aaron.axvig, Sat, 02/01/2020 - 12:37

We spent a week and a day on South Bimini until the weather was right to sail east.  On the first day I did customs and immigration at the airport in the afternoon.  Then we started meeting all of our new neighbors; about 12 boats had arrived to the marina with us that day, and it was almost empty previously.

We spent some time marveling at the comically clear water.  It was about 10 feet deep around the docks and we could see perfectly to the bottom.  There were lots of minnows, plenty of 6" fish, and even some 12-18" ones.

The first or second day we went to North Bimini to see what it had to offer.  Louise came with to help.  The dinghy parking situation was not that good, just an aluminum swim ladder on a beat up concrete wall, with the east winds making some weird little waves to push our dinghy into the wall.  We walked around for about an hour.  Very interesting.  There was what appeared to be the power plant of the island, which I think was just a large diesel generator.  It makes sense that the marina charges $30/day for power, and we have seen some that have meters and charge $0.80/kWh (4-8 times what you might pay at a house in the US).  There were some grocery/convenience stores, some just small rooms absolutely packed full of packaged/canned food and some with a little more organization and potatoes, onions, etc.  Most prices are double that of an average US grocery store.

The no-see-ums were really bad the first two nights, but then it was pretty windy so they weren't a problem.  House flies were not deterred though!  We had to keep screens in most of the time--they block some airflow and make it tedious to go in and out.  We made a habit out of taking Louise to the beach by the marina in the late afternoon.  She would chase the tennis ball and I would look for beach glass.  The first time we went to the beach Anna couldn't find her phone when we got back to the boat.  So we went to the beach to look, and eventually I found it about 18" below the surf.  It still worked...for about two days.

I read six books in six days.  We did lots of crossword puzzles.  We watched the Vikings play (and lose) at the Thirsty Turtle, a bar a five minute walk away.  They had a pizza oven but were not able to get supplies to make pizzas before we left, still in the process of opening after renovations.  The marina had a new owner too.

One of the other boats in the marina was SV Twin (that we had crossed paths with as we approached Bimini) and they have the same model of boat as us.  This was the first time we had seen another one (excepting the one we looked at in Port Charlotte, FL when we were boat shopping, and one that we saw in passing at the marina where our boat's previous owners kept our boat) so we had a lot of fun touring theirs and showing them ours.  There are so many interesting differences!

For internet connectivity we could use the Wi-Fi at the marina office or at the Thirsty Turtle.  And probably half of the days I would take my phone out of airplane mode, resulting in an automatic $10 charge for 24 hours of great roaming connectivity (set up with Verizon ahead of time, some people were doing the same with AT&T too).  We had a Wi-Fi hotspot device with unlimited data waiting for us at Great Harbor Cay so we were looking forward to getting that.

The marina gave us a prorated price of $150/7 for our eighth night there and the next morning we departed at sunrise for Great Harbor Cay.  It was 80 miles to travel and we were going straight into a 10-15 knot wind and two foot waves.  Sometimes the bow would slam on a wave and Louise would get really scared.  Into waves and wind is not great for speed and it was a long ways so we ended up anchoring in the dark at 10:30pm.  It was an easy approach and a wide open area to anchor so not too bad.