Thursday, April 17, 2014


There is no single right way to configure all boats to make water.  There is just the right way for you and for your circumstances.  You could go with 12 volt, engine driven or a 110 motor, with multiple membranes or just one, or with automated controls or manual.  You could even use a hand pump to make fresh water from salt water, if you are trying to stay in shape, take very few showers and plan to do nothing else with your time.  But then you would not be reading this post.

We have our reasons for the choice of configuration we made, or at least ended up with.  Some things at the start were different than at the end.  But it works for us and you have to figure out what will work for you.  As we describe our configuration, we will try to also give reasons, which may help you make decisions as to your particular setup.

*** Whatever you do, it is yours to do.  We have simply described our setup after multiple requests for this information from cruisers.  We are not responsible for your work! ***

Our first time cruising was on the U.S. west coast and in the Sea of Cortez back in the 90’s.   We had a small 12 volt water maker that produced under a gallon an hour.  We supplemented this noisy trickle by purchasing questionable water from local sources and hauling it back to the boat in our dinghy.  In setting up our second cruising boat, many things we previously considered luxuries were promoted to necessities.  Having a lot of water on board was at the top of the list.  As many of our sailing friends know, we are not in a perfect sailing world.  We may have to turn on the engine until the wind comes up or after the wind dies out.  We have found this to be true especially in the Bahamas and the eastern U.S.   Based upon the fact that we recognized motoring would be a part of our cruising life, that we did not have a built in generator, and that we wanted to make a lot of water per hour, we chose the way of an engine driven water maker.

We have an 80 HP Ford Lehman motor in Hold Fast.  That motor lugs along and presents no noticeable difference in performance if we were to run a pump to push water through one membrane or through three.  We found a bulkhead where we could mount three membranes and it seemed to us that three was better than one.  Not only could we make 55 or 60 gallons per hour with three membranes as opposed to 24 GPH with one, but it would also allow us some redundancy in the event one of the membranes failed.

There are nice 12 volt systems out there than almost run themselves.  They run for a period of time and then flush themselves.  On Hold Fast, we have tankage for almost 300 gallons of water.  This allows us a period of two weeks or so between making water.  Given that simple is better when building something yourself and that manual is more simple than automated, our system is manual.  First of all, there is no clutch on the pressure pump.  When we want to make water, the engine is shut off and the belt is installed, then the engine is turned back on.  To stop making water, same thing: engine off, belt removed, and the engine is restarted unless we are sailing.  Secondly, all product water goes down the sink until our total dissolved solids reads 300 or less AND the water has been personally tasted and approved by the captain.  Once approved, the product water is manually switched to fill one of the three tanks aboard Hold Fast.  And finally, we flush the system by manually turning a valve and turning the water on for a timed period, the timing of which is dependent upon whether it is an initial flush after making water or a secondary flush. 

Now you see the reasons for our choice of an engine driven, three membrane, manually operated water maker system.  We also have a secondary RO water system for drinking and cooking water, but that is a matter for a different post.

Feeder Pump – We have a Shurflo Blaster 3.5 Washdown Pump, purchased from West Marine.  It pumps 3.5 gallons per minute.  We no longer see the part number sold, but a pump along these specifications will do the job.  The primary concern with this pump is that it must have output that is greater than the input requirement of the pressure pump.  The pressure pump must never run without water.  In our manual process, the feeder pump is turned on before we start the motor and turned off only after the motor is stopped.  We put a Y-Valve on the feeder pump and use it alternatively as a wash down pump.  We did not choose a centrifugal pump, as that type of pump can sometimes lose its prime.  We are on our fourth year utilizing the same pump for both wash down and to supply water to the pressure pump. 

20 Micron Filter Housing and Filters – The raw water must be filtered of any large particulates that might damage the high pressure pump.  Our 20 micron filter is the first in a series of two.  We purchased the housings and all our filters at US Water Systems, particularly Harmsco Water Better pleated filters SKU 545-WB-20W.  Their inexpensive filter housings are just under $12 each.

5 Micron Filter Housing and Filters – The 5 micron filter is the second in the series of two between the feeder pump and the high pressure pump.  Again the housing and filters were purchased at US Water Systems, only the 5 micron filter is SKU 545-WB-5W.

Here is a picture of the Filter Housings.  The Feeder Pump (Blaster) is below the housings with a yellow handle on the valve to select water maker or wash down.

Pressure Pump – We used General Pump, model number TT941, with a flow of 3.43 gallons per minute at 2,800 RPM.  It was purchased from Pressure Washer Authority.  This pump is a forged brass manifold pump.  We know it will not last the life of the membranes, but at $232.99 each, you can easily carry a spare (or two) as opposed to paying about $1,500 for a stainless or bronze pump. 

Alternatively, Model TT9111 ($248), which runs at 3 GPM, should match up with some electric motors if your configuration involves a generator.  If you plan to start with one membrane and expand, you should consider the small additional cost of a higher flow pump.  Dow Water and Process Solutions has a free software for download: Dow R.O.S.A System Design Software, that you may use to help size your pump.

Here is a picture of the Pressure Pump with belt installed for operation:

Engine Bracket – This part of the installation required some technical expertise in designing the pump bracket.  We laid out where we wanted the pump and the pulley alignment, and then drew the bracket design.  We had our friend and master craftsman, Rich on Morning Star, tack together the bracket, which we then installed, made some adjustments, and then had him weld it together.

Membranes and Housings – Our membranes are 2.5 inches by 40 inches, purchased from American RO, part number SW30-2540.  The price for the membrane is $180 for quantities 1 through 5.  The housing we used, PV-2540-SW (ACT) cost about $415 each.  We got the ACT ends because they will not corrode in our environment, which is a possibility with the aluminum ends. 

As a side note, American RO also had a link to the Dow R.O.S.A System Design Software, something mentioned above. 

Mounts – We used pipe wall mounting hardware from McMaster Carr to secure the membrane housings to the bulkhead.  Our best space on the Whitby42 was below the galley floor just forward of the engine room.

Here is a picture of where we mounted the membrane housings.  You can also see the blue pressure tank for the secondary RO system, again a subject for a different post.
High Pressure Line and Fittings – After measuring the lengths required, we ordered high pressure braided chemical hose, SKU 52515K3, FDA food grade, from McMaster Carr.  We used the brass flared fittings.  These same items may also be ordered from Discount Hydraulic Hose. 

Pressure Gage – The control of pressure controls the quantity of water produced.  We ordered our high pressure gauge from McMaster Carr.  The gauge goes up to 1,000 PSI and is glycerin filled.

Needle Valve – The needle valve is used to increase or decrease the pressure on the membranes.  We now use a 316 stainless steel needle valve called a Mini Valve, purchased from McMaster Carr for about $62, part number 7833K96.  We recommend 316 stainless because we tried a brass needle valve and it did not last very long.

Water Quality Monitor – Our water quality monitor is inline and gives the total dissolved solids of the water exiting all the membranes.  We purchased this quality monitor from Wateranywhere.  It is a Dual Total Dissolved Solids Meter (Dual TDS) made by HM Digital, part number DM-1 at about $30.  You could use something similar, like an SM-1 which is $25.  Or you could use a hand held meter, but we wanted ours inline, and the price is not that much different.

Flow Meter – Our flow meter shows how many gallons of product water are flowing out of the membranes.  We did not put a meter on the flow of the brine water.  Ours is a panel mount flow meter made by King Instrument Company that shows up to 75 GPH.  We purchased it from McMaster Carr for about $58.  You can select Part #4351K121, and then you must choose the flow rate to suit the system you are building.  A meter with a smaller flow rate could be used for a one or two membrane system.

Coconut Charcoal Filters – You will need a filter fit for removing chlorine from your tank water for the flushing of the pressure pump and the membranes.  It is prudent to always assume that chlorinated water has made its way into and resides in your tanks.  We use a coconut charcoal filter purchased from the same place as our other filters, US Water Systems.

Start Up – As mentioned earlier, before start up of the engine, the belt is put on the high pressure pump and the feeder pump is turned on.  We check to make sure the feeder pump is working water through the system by confirming that water is flowing out the brine through-hole and that there are no air bubbles.  The portion of the system that feeds water to the high pressure pump is visually observed for leaks.  Once the engine is started and engine specs check out normal, the RPM is brought up to 1,300 or just below.  The high pressure pump is designed to run at 2,800 RPM, therefore we sized the pulley on the high pressure pump so that the RPM on the Lehman would be 1,300 RPM, a good motoring speed for Hold Fast, which would run the high pressure pump at 2,800 RPM.  This 1,300 RPM represents the top end limit for motoring when we are making water.

Applying Pressure – By turning in the needle valve, pressure is increased to the membranes.  Dow recommends you take 60 seconds to bring the membranes up to operating pressure.  If you are using your membranes for the first time, you should consider taking two minutes.  Operating pressure for us depends upon the salinity of the water.  We bring it up to make 50 gallons an hour and let it stabilize for about 10 seconds, making sure the pressure on the guage never goes over 1,000 PSI.  Normally the pressure is 750 to 800 PSI.  Once stabilized, the needle valve is again turned in until we get 55 to 60 gallons per hour and that is normally at 800 PSI.  If we only had one membrane, the rate would be about 24 GPH, and if we had two membranes, the rate would be about 40 to 42 GPH. 

Product Water to Tanks – Once the water maker is producing 55 gallons per hour, the Dual TDS Monitor is turned on.  When it is first turned on, the TDS will read somewhere above 300, but it will quickly move down to 300.  When it hits 300, the water is tasted, if it tastes good the water is diverted from the sink to the tank.  A note is made as to the rate of water production, say 55 gallons per hour, and a timer is set.  We have our ways of knowing when each tank is full.  A valve is turned to change which tank receives water until we have made our desired amount of water, or until all the tanks are full, or until we are done motoring.

Here is a picture of the TDS Monitor, Flow Meter, Needle Valve and Pressure Gauge.  Please note this picture was taken while we were making water on the Chesapeake, which has less salt and requires less pressure (under 400) and the water product has fewer TDS (061 parts per million). 

The picture below was taken when making water during a passage from Provincetown, MA to Shelburne, NS.  The water temperature was about 47F.  In accordance with the membrane manufacturer's specifications, cooler water will give a product with less TDS.   The rate of production is just under 60 GPH, at a pressure of around 750, producing water with 114 TDS. 

Please note, when the membranes are used for the first time after pickling or the first time ever, it will take 45 minutes (or more) to clear the pickling solution from the system.  We flush after pickling only using the feeder pump, as recommended by Dow.  

Shut Down – Prior to shutting down the water maker, the product water is diverted to the sink again and the needle valve is slowly backed out, taking about 60 seconds to do so.  With the needle valve completely back out, the system is run for 3 to 5 minutes, giving the system a saltwater flush.

Flushing – Within 24 hours of running the water maker, both pre-filters are removed and rinsed with fresh water.  The charcoal filter is placed in one of the pre-filter housings. The tank water is used to flush approximately seven gallons through the system.  The charcoal filter typically flows at one gallon per minute, therefore the flush lasts seven minutes.  After flushing, the charcoal filter is removed and rinsed with fresh water.

Whether or not we are away for the summer, we still pickle the water maker system once each year.  The annual pickling is recommended by Dow to keep the biological count down in the membranes.  We use the same product used in the wine industry.  It is called Sodium Metabisulphite and we purchased it in bulk from LD Carlson Company out of Kent, OH.  We say ‘in bulk’ because what was delivered to us will last ten years or more since we only use 2 ounces per gallon of water and it only takes five gallons per pickle (or ten ounces of sodium metabisulphite).  If you have a pressure pump from Spectra, DO NOT use this chemical for pickling, it will damage the pump.  There are no pre-filters in the housings when we pickle.

We have no delusions that we have answered all your questions.  You must spend time to study the subject on your own.  If something we have written seems unclear, please leave us a comment on the blog along with your email address.  We would be glad to get back to you.

May you have fair winds, following seas and fresh water.

1 comment:

  1. Thanks for the detailed write up. We may use some of this when we get around to installing a Watermaker on Joie de Vivre.