Under the deck water fills, use a water filter, add some Clorox every now and then, and taste it for salt contamination. If it tastes good, it has less than about 500 ppm salt contamination, which is the world health standard for drinking water.
Then use something like a
Sea Gull IV filter for
drinking water bugs. If you are cruising in the Carib or further out you
won't have time to double filter every time you need water, and it is not
necessary. Especially if you are taking on rain water.
"Tell me more about rain water collection while cruising. What do you do
with it after it enters the boat? Does it get filtered? Do you put directly
into your water tanks?"
Our pressure water system has a 20 micron filter before the
galley feed, and a Sea Gull IV
filter on a separate tap used only for drinking water.
We have a have deck shower aft with a quarter
turn shut off valve at at the deck and use a kitchen sprayer for the working
end. We use about 15' of hose so that we can FW wash the dinghy, flush the
outboards and wash down spills on the aft deck and cockpit if needed. I've
been using that now for 10 years.
2015 Update: We sold our CSY in 2015 and moved to a Catamaran. We have installed a similar system on the cat.
Also see our Presentation on Making Our Own Watermaker
Why Engine Driven. Since we carry only 165 gallons of water, and may be at sea for up to 30 days, we decided to install a water maker. I've used a small (6 gallons an hour) 12 volt water maker previously, and it was a real pain running it daily or for hours at a time to keep up with our 6-7 gallon a day usage. Besides that, it needed 17 amps per hour to make its 6 gallons of water.
Some more modern units make about a gallon of water for each amp hour used, but they are very expensive and not easily owner repairable in the field.
Several years ago I saw two home-built units using a commercial HP plunger pump run off the main engine and two of the large membranes producing about 40 gallons an hour. These were each built for around $2K. A similar store-bought unit would cost around $8K and a kit unit about $5K.
So for a savings of up to $6K, and in order to learn more about these systems, I decided to build my own mechanically driven unit. Mine is powered by the main engine since we don't use a generator, but it could also be powered by a generator or an AC motor of about 1.5-2 HP. DC motors aren't available that large, so are not an option. For many reasons I stayed away from using electronic/ automatic control systems, except the electric boost pump, and used only reliable mechanically operated components.
The System Diagram. Above is the diagram of my entire system with all the components shown. (Click on picture to enlarge) There are many ways to lay out a water maker system and different opinions as to what is needed and what is nice to have. I've looked at lots of water maker system diagrams, talked to most of the manufacturers and discussed the fine points with many owners.
While building my system, I stayed away from electronics and automatic systems/sensors because of extra expense, complexity and the high failure rate of electronics in a hot engine room. Also, a lightning strike would certainly kill a system with electronics. So my system is all manually controlled and monitored, since I will be onboard and actively running the system while it is operating.
Equipment Options. Here are my opinions on some of the options available when buying/building a water maker system. These ideas are based on what I have read and discussed with many knowledgeable water maker people.
The HP Pump. Cat, Giant, HyPro and several others make good plunger pumps that can be used for a water maker system. I originally installed a two plunger Grainger Teel 2P414D (made by Hypro as a 2230B-P) mainly because it was available used at a good price from a friend. It turned out to be barely adequate for our 40 GPH system.
Because I wanted better flow for good scouring and to ensure full output from the membranes I have since installed a 3 plunger pump (the Hypro 2345B-P, rated at 4.7 GPM but really producing 5 GPM, about $325 new on the internet at www.deindustrial.com June 2008). This also allows me to retain the smaller pump with the same mounting foot print as a backup. (note: as of 2010, deindustrial is out of business, see our Watermaker Links for updated source).
Rather than using a very expensive Stainless Steel or Titanium head HP pump I am using significantly less expensive but entirely suitable bronze head pumps. I am told by several experienced dealers that these should be good for at least 1000 hours of use before the high pressure pulsations with salt water might damage the pump head. At 40 gals an hour that's 40,000 gallons I can make before I can expect the risk of a pump head failure. At 10 gallons a day usage that is about 11 years of use if I use RO water every day. We won't be using RO water every day and there will be at least a couple of months a year when the system will be in layup while we are away from the boat on travel. Given the cost differential, roughly $300 for a bronze head and $1500 for a SS head I am using bronze.
The pump pulley has been sized to allow the pump to run at 1725 RPM when the engine is running at 1400 RPM. The pump will produce its maximum output at that RPM and the engine is comfortable under way or at anchor at 1400 RPM. Since the big pump can produce the full rated 42 GPH through the membranes at about 700 PSI I can run the engine at less RPM if needed and still produce the full rating of product water by simply raising the pressure setting a bit. I have accurately calibrated my engine tachometer and can monitor the engine and HP pump speeds with my handheld electronic tach.
Rather than use an electromagnetic clutch to control the on/off switching of the HP pump I decided to use a manual system with a custom-built SS vertically sliding tray for the pump under the engine front pulley sheave. This decision was based n the following:
It is a relatively simple matter to raise the pump up to attach the belt to the single engine sheave. By pushing lightly down on the pump and locking it in place with wing nuts the belt tension can be set as needed. This setup produces a fool proof, non electric, no-spares-required system.
In water maker literature some flow specs are given in GPH and others in GPM, so convert when necessary by dividing GPH by 60 to get GPM.
The feed input is the sum of the brine and product outputs, since all the water coming in goes to either product or brine. The product output divided by the feed input gives the recovery rate.
With the original smaller HP pump, under operating conditions I planned to run the unit at 1725 RPM, 825 PSI, 2.5 GPM brine output and 40 GPH product output. That assumed I would have 3.2 GPM or 190GPH input from the HP pump to work with. It is rated at 3.0 GPM but really produces 3.2 GPM.
I arrived at these operating parameters by calculating the maximum recovery rate I could make while remaining within Filmtech specifications for long membrane life (max 1000 PSI, each 2540 membrane 21 GPH product flow). The max recovery rate for each 40 inch membrane is 13 percent, so for two membranes in parallel you get 26 percent. A better figure to use without stressing the membranes over the long term is 11 percent each, 22 percent total.
The calculations are as follows.
40 GPH product output divided by 190 GPH feed input (40 GPH product plus 150 GPH brine outputs) gives 20.6 percent recovery, well within specs.
In order to maintain proper scouring/flushing of the membranes at least 2 GPM feed flow is needed, with 4 GPM being much better for long term use. So for the small pump 3.2 GPM (2.5 GPM brine plus .67 GPM product outputs) is OK. For the larger pump, 5 GPM is much better.
the above, and my own testing at different pressures. I could run the system
with the small pump up to 850 PSI and make 43 GPH at 22.2
percent recovery, but that is
just above the max I've seen recommended for long term use. Filmtech says
the max operating pressure for their membranes is 1000 PSI. 825
PSI is slightly below the recommended max and and well below Filmtech's max,
and it still produces almost as much
fresh water (40 GPH) as running it at 850 PSI. The Jabsco boost pump runs at about 8 PSI
while the system is operating, providing adequate positive pressure against
the HP pump head.
The original HP and LP pumps together pump 3.2 GPM feed under normal operating load. With the larger new pump the feed flow under load is almost 5.0 GPM when pressurized. And it will allow the maximum product flow through the membranes, 42 GPM, 22 percent recovery, at just 700 PSI. This leaves a significant room for pressure increase in order to maintain product flow and good scouring as the membranes degrade over time. So, as of late Sep 08, I am using the larger pump in the system with the smaller pump stored for backup.
The HP pump is engine driven, requiring about 1.5 HP for the smaller pump and just over 2 HP for the larger, and is capable of producing a bit more than 40 gallons per hour from the two 40 inch membranes. At that rate we can run the system once a week for about hour and make up our week's water usage. Running the system once a week with a fresh water flush at the end is a good long term regimen for the membranes. Much longer and there will be problems with biologic contamination.
The only electrical part is the 12 volt Jabsco Water Puppy boost pump. I have moved the membranes from the engine room, where the temps in warm weather reach about 120 degrees F, to the aft head where it is much cooler. The Filmtech membrane data sheets indicate the max operating temperature should be no greater than 113 F.
While I was at it, I added a salt water manifold for the deck wash Shurflow Blaster pump, the Marsh 809BR refrigeration cooling water pump, the Jabsco water maker boost pump, water maker cleaning/lay up and fresh water flushing and a fresh water crossover for flushing the manifold and running the refrigeration while on the hard. I also installed a new opening port into the engine room in order to provide some natural ventilation.
The lay up solution (2 tbsp sodium metabisulfite per gallon of water) is sucked out of a 5 gallon bucket through the manifold cleaning system valve as shown on the diagram. The same system is used for the two cleaning solutions. If you start with the system fresh water flushed and full of fresh water, I calculated the system holds about 2.5 gallons of water when all the lines, pumps, membranes and filters are full. Therefore, with the bucket about half full, any mix should be calculated for about 5 gallons.
Regarding cleaning solutions, I've been advised to be fastidious about keeping the membranes clean, away from any petroleum or chlorine products and flush after every use rather than rely on cleaning products to clean the membranes. The membranes can only take a couple of cleanings before they will be permanently damaged and exhibit degraded output.
Additional Info Resources. The original source for much of my inspiration came from another boater. This was originally online here: www.Rutuonline.com. Rutu built his own system using similar components to mine, but with much more in the way of automatic/electronic control systems. His description of how he selected components similar to mine was excellent. However, this site is no longer active. I have recently found another site here: Leo Lichtveld's site.
A second very helpful source is the AquaMarine, Inc website. AquaMarine sells do-it-yourself kits, also using similar components. Both have good detail on equipment choices and installation tips. AquaMarine has a great installation and operating manual, a copy of which might be obtained from another Aquamarine owner.
Also, there are numerous commercial water maker sellers that have websites and handout material of some usefulness. See here for more links to watermaker info and parts suppliers.
Below is a list of the major parts I used and some pictures of the water maker project under construction and as installed on Soggy Paws.
Major parts list:
on the fresh water tanks in the Walk Thru model.
There's not much more
important while cruising than good drinking water. So we took the time to
try to do a safe, efficient system. It is well worth the effort to spend
some time with your head in the tanks and bilge checking out and cleaning up
your system. Our last project will be to add an engine driven large capacity
water maker before we head out again.
Two easy projects that gave us much better control of our fresh water system were installing a fresh water manifold under the companionway steps and replacing the check valves with quarter turn ball valves between the side tanks and the centerline tank.
The manifold project involves bringing all the supply hoses from the fresh water tanks out of the bilge through predrilled holes in the floor so you can mount a neat white PVC manifold with 3/4” quarter turn valves under the bottom companionway step. My seven valves are all arranged horizontally under the manifold with the inlets/outlets at the bottom and the manifold running between them at the top. Port to starboard the valves are for:
Located here you can easily see which water tanks are on line and which supply system is being used. This system allows you to draw from each tank individually and use either the automatic pump or a manual foot pump in the galley to pressurize the system.
By replacing the bronze check valves in line between the settee tanks and the large centerline tank with 1-1/2” white PVC quarter turn valves you get much better control and isolation capability for all your FW tanks. These valves, suitable hose and PVC pipe and fittings are available at any good hardware store.
Several years ago I read an article
describing a vertical arrangement for multiple electric bilge pumps in a
deep bilge. There was a small automatic pump at the very bottom which kept
seepage water to a minimum. The next higher pumps were large and for
emergency use. I adopted the arrangement and added the standard large CSY
manual pump and a Y from the engine raw water pump with a custom PVC foot
intake to the mix. I also added a high bilge water alarm sensor just above
the small electric pump. All the electric pumps, the alarm sensor and the
manual pump foot valve are mounted on the standard CSY aluminum angle mount.
I sealed up 3 small discharge thru hulls in
the side of the boat rather than remove them. What I did was drive an
appropriately sized epoxied wood dowel in from the outside and installed a short
piece of plugged strong hose on the inside. Now there is only one
discharge through the side of the boat, the manual bilge pump as the
refrigeration cooling water discharge has also been plumbed to the cockpit.
By increasing the diameter of the cockpit
drains to 2" and using bullet proof Tigerflex hose and bronze fittings for
the drains, it seems to me that using the cockpit for the drains, presents
less potential for a problem than running them through the hull at the
waterline. Who knows what might happen in a roll over, but at least I will
not have two more holes in the hull without seacocks.