Water Maker Installation

Posted by John

We decided to stay in the marina in La Paz through the end of the year. We had a water maker to install, a dog to take care of, and two boats to keep an eye on for friends who flew home for a few weeks over Christmas. Our crappy little dinghy doesn’t handle even the smallest wind waves very well, and the way the wind picks up at times we wanted guaranteed shore access with a limited amount of excitement. Anchoring out just seemed like such a bother.

Marina de La Paz, one of four main marinas used by the cruising community here, is one of the most convenient marinas we’ve ever been in. Unlike most of them we’re used to at home, which often seem to be out of the way at the end of a road and not within walking distance of much of anything (partly due to local terrain), this marina is within easy walking or bicycling distance of restaurants and shops of all kinds, as well as the waterfront of central La Paz. The marina is not huge, which is part of what makes it nice. All of the marina amenities are right at the end of the dock, with power, potable water and wired high-speed internet at each slip, plus wi-fi. A marine chandlery, with a surprising amount of stuff in their back room, is directly across the street. Another one is a several block walk away, but it seems to have an even larger variety of parts. A small convenience store, self-serve or full-service laundry, government paperwork office and a dive operator are all within the walls of the marina.

Several other boats from the Baja Ha-Ha, including some of Robyn’s friends, have also been around. A mile or so away is a supermarket with a movie theater in the same building. Robyn reports that not only do the seats recline, but they have a call button which brings an usher to take a food order or bring a blanket if the air conditioning is a little too much. She and her friends have also been to museums, a pool party, and even went with a guide to snorkel with whale sharks. Whale sharks are not whales, but are plankton eating members of the shark family and, at up to forty feet long, are the biggest fish.

It was Robyn, then, who agreed to dog sitting and boat watching over Christmas. Once this had been arranged, we knew we were staying for the duration. Rover has been great fun, and he’s helped us meet so many other dog owners. However, all is not fun all of the time. We have a water maker to install.

A water maker is a small desalination system for extracting drinking water from seawater. Water makers work on the principal of reverse osmosis. As a kid, when I didn’t do my homework, my mother frequently spoke of osmosis, as in, “Do you expect to learn that through osmosis?” But she never explained what it was, and I never asked. Or maybe I did and her explanation just didn’t stick.

As I understand osmosis now, if a solution of dissolved solids, such as seawater, is on one side of a semi-permeable membrane, and a solvent, such as water, is on the other side, molecules of the solvent will, over time, tend to move through the membrane to the other side. This results in less solvent and more solution. The online Khan Academy has a short video explaining the theory of osmosis in a way that makes sense even to me, but I don’t see how my mother could’ve thought I might learn anything through it.

Osmosis – Khan Academy

The goal of an RO water maker, therefore, is just the opposite, or, “reverse osmosis.” Reverse osmosis requires energy. A water maker pressurizes the seawater to force water molecules through the membrane, leaving the dissolved solids behind. Then again, except for the magical and expensive semi-permeable membrane, I’m not sure what “reverse osmosis” actually has to do with normal osmosis. Why not just say it is a really good filter?

We chose our water maker from Cruise RO Water and Power, in part because their systems do not come as one big, chunky box that needs a big boxy space to put it in. Instead, the system is made up of mostly commonly available component parts that you assemble yourself and install wherever they fit. Below is a simplified schematic of the basic system components for the Cruise RO Water, 30 GPH system.

Not shown in the simplified schematic diagram is the control panel with pressure adjusting valves, product water flow meter, power switches and water sample valve. The 30 GPH model uses two RO membrane assemblies in series, as shown. The first membrane can extract about 20 gallons per hour, and the second about 10 gallons more.

If the water maker is not being regularly used, then every few days it needs to be flushed with fresh water to prevent organism growth. The flush water is run through a carbon filter to remove any added chlorine that would be present from a municipal system. Chlorine will damage the membranes. For longer periods of storage, a pickling solution is pumped through the system. One of Robyn’s assigned boat sitting tasks is to periodically flush their water makers.

For our source of seawater we chose an otherwise unused seacock located inside a storage cabinet in the head, forward in the bow. This seacock had formerly been used as a source of toilet flush water, a saltwater foot pump for the head sink, and potentially as a water source for an anchor wash pump. We had disconnected everything from it years ago, and replaced the seacock when we replaced all of the seacocks in 2011. At that time it was capped off and left unused. The seacock connection is a one-and-a-half inch pipe thread. We needed to find bronze fittings that would get that down to a half-inch hose. Finding those fittings was a separate adventure at a La Paz industrial plumbing supply outlet.

We had been told to go to El Arco Plumbing by the owner of La Paz Cruiser’s Supply, an ex-Seattleite who is also the local Cruise RO Water dealer, and is quite knowledgeable in water maker installations. He drew us a sketch of where the bins of bronze fittings were located inside El Arco, behind a service counter. He said to just walk in there like we knew what we were doing. We would not be able to adequately describe what we wanted in Spanish.

No matter what you’ve sketched out on paper, there will always be something you can’t find but possibly can be substituted for with a minor design change based on what’s available in the store. With ongoing mental redesign while standing at the wall of bins, we eventually found most of what we needed to reduce the inch-and-a-half seacock inlet down to a half inch hose barb. We also found a few other parts we needed for the other connections to the water tanks and the fresh water flush. We took them to the counter where an employee looked each one up in the computer and printed out a ticket with the price totaled. But then we no longer looked like we knew what we were doing. He wouldn’t take our money or let us take our parts. It turned out that we needed to take the ticket to the cashier and then come back with the receipt. How embarrassing it was when I couldn’t see the cashier behind the darkened glass in the booth in the middle of the room even with half the employees pointing at her. I could see all their lips moving, but I couldn’t understand a word anyone was saying. The booth was in an odd location and looked more like a product display than a place to hand over cash. Eventually we got it all figured out, took our prized baggie of plumbing parts, and found our taxi still waiting outside.

We ran the reject brine discharge line through a couple of cabinets and then under the cabin floor to the engine room. It exits the hull high above the waterline through what we think used to be a bronze fuel tank vent that had been disconnected and unused since before we bought the boat. It took all of the thirty feet of brine discharge tubing that came with the water maker to make that run. The fresh water output from the membranes runs through a “Y” valve on the control panel and is sent to either a test port or into the water tank manifold under the galley sink to be fed to one of our three water tanks. That tube also runs under the cabin floor. The sample port is the outlet spigot in the head sink formerly used by the old saltwater foot pump. I had to drill several holes in order to run that tube.

Since the incoming seacock is located inside the head we also chose to locate the boost pump there in an awkward, under-used space across from the toilet. We put the 20 and 5 micron pre-filters and the carbon filter there as well. We tied into the head sink water supply to provide the source of fresh water for flushing the system.

The purpose of the boost pump is to feed water to the high pressure pump at an adequate rate. We mounted the high pressure pump on a shelf in the main cabin, just outside the wall between the cabin and the head. The high pressure pump is heavy, so we beefed up the shelf with a spare half-inch-thick piece of plywood we had been carrying. The shelf is long enough to also accommodate the membrane housings, which are about four feet long. Two reinforced high-pressure hoses with swaged fittings on each end come with the system. One is three feet long, and the other is five. One connects the pump to the membrane assembly input, and the other connects the membrane brine output to the control panel high pressure gauge. We also fit the control panel onto the shelf, building a wooden frame on which it could be mounted.

To get the wood for the frame we took a trip to The Home Depot. Having built a couple of houses for ourselves, we are quite familiar with Home Depot and what they carry. But this is Mexico. We had heard mixed messages from people who had been to the La Paz Home Depot. The opinions ranged from, “They have everything you’d expect in a Home Depot,” to, “Don’t expect what you’d find in the States.” When we asked specifically if we could buy a board there, the answer was, “Sure, as long as it’s pine.”

When you first walk into the La Paz Home Depot it looks like any other. It’s only when you try to look for something specific that you start to get frustrated. With a taxi waiting outside in the parking lot, we couldn’t spend time trying to shop for the other projects we have lined up and needed to focus on what we came for. The lumber selection was, indeed, somewhat limited, especially in the area of trim or shelving. We were looking for a 1 x 4 that we could use to make a frame to bolt to the shelf and hold the control panel in a vertical position. The taxi was too small to carry an eight-foot board, so we hoped Home Depot would cut it for us. We found a 1 x 4. Well, it averaged out to a 4 inch width, anyway. It was a little less at one end and a little more at the other, but good enough.

Home Depot would, indeed, cut the board for us, but it was not as easy as just asking the nearest clerk. There was a window to go to, a ticket to fill out, a lot of gestures and pointing and confusion. Then we had to take the ticket to the check-out line and pay before going back to the window to have the board cut. There were other cuts for other customers ahead of us until finally, we achieved success. Once you know the process, either for the plumbing supply store, or Home Depot, it makes sense. It’s just not what we’re used to. Normally at Home Depot we’d just ask an employee if they could cut our board in half and they’d just do it and hand it back.

I suppose if we had still been at home with lots of time to plan and do, maybe even with the boat in a yard, and certainly not fully loaded with too much stuff, we would’ve laid out the system differently. The Westsail 42 has places where the water maker components could be mounted with space for the control panel nearby and the various hoses and filters all hidden away but still easily accessible. But we aren’t doing this at home, or with all the time in the world, or with a full compliment of tools and workbenches. If we had taken the time to do everything we wanted to do in the way we wanted to do it, we’d still be dreaming of our someday trip. No, we are underway, albeit stopped for a few weeks, and in Mexico, no less. We may not yet be living the definition of cruising—working on the boat in exotic places—but we’re starting to get the feel of it.

Meanwhile, our time in La Paz is running out and we’re likely to be leaving soon.