We're now into our final year before heading out on our adventure. We still have a few items to get for the boat and we've set up a budget to manage this. One thing we 'll need is a water maker. We had picked one out at the Boat Show last year made by Spectra. It makes something like 8 gallons per hour, runs almost silently, is totally automatic and costs around $6,600. This sounded almost affordable at the time but as we get closer to our departure date we're beginning to narrow down our needs. We decided that 8gph just wasn't enough for our lifestyle, that we really needed 2 to 4 times that. We don't want to be running this thing all day and night and that's really the kicker. Living aboard at the marina we routinely go through 250 gallons per week or 35.5 gallons per day. That's pretty wasteful for most live-aboards but over the last four years that's been average for us. We're OK with that.
When we're out cruising we most likely won't be making water while at anchor in a busy harbor. A lot of people just pump their crud overboard and the water in a harbor can be pretty filthy which would clog up our filters pretty quickly. If we can get by on a full tank of water for a week while at anchor then we could just refill it while we're underway. The issue then is that we'll need to make more than 8 gph. Spectra makes larger water makers but the price goes up quickly. For a 16 gph unit we're looking at about $12,000 which puts it cleanly out of our reach.
Because of this and the fact that I enjoy making stuff I started looking around for some Do-It-Yourself info. On the internet you can find anything and sure enough, I found two really excellent articles on how to build your own water maker. One uses a high pressure pump from an industrial pressure washer and makes 40 gph. The entire system can be done for under $3,000. Now we're talking! The only concern is how much noise does this thing make? Our neighbor down the dock has a water maker and you can hear it from a mile away. I couldn't bear that and would be willing to pay a bit more for something quieter. The second system is more automated using sensors and relays to protect the system when the pre-filters get loaded. This second system also runs with a pressure washer pump but has several suggestions for alternatives, all costing more money but providing less noise and less maintenance. With the cost of a better pump this system can be had for less than $4500.
I think I'll combine ideas from the two systems. We already have a thru-hull and basket type strainer that's currently used only for the deck washdown system. I think I can safely tie into that just beyond the strainer and not have to run the two systems at the same time. From there we'll run a line to a feed pump that provides low pressure flow to keep water going into the high pressure pump. We're going to use a magnetic drive pump here that'll be virtually maintenance free. It's a Blueline 70D and runs at 12 psi and 4 gpm. This will feed into two pleated synthetic pre-filters, a 20 micron and then a 5 micron. From there it runs into the high pressure pump for which we'll either use a Cat #247 or a Hydra-cell D10. The Cat is a pressure washer pump that runs at 1200 psi and 3.6 gpm. It's biggest drawback is that it's noisy and introduces vibration into the system. The vibration can be taken care of but the noise is another matter. Right now I have an RFQ (request for quote) into Hydra-cell. Their pump is used in industry for moving all types of fluids and the beauty of it is that it has no seals and it's operation is simple so it's basically maintenance free. And noise free. If we can afford it this is the pump we'll be using. The pump output runs into the reverse osmosis membranes and pressure vessels. To get 40 gph we'll have to use two of these, each being 2.5" x 40". There are two outlets from each pressure vessel. One will feed into a pressure regulation valve which will keep back pressure at 800 psi which is necessary for the whole reverse osmosis thing to work. The other outlet will feed through a flow meter and then dump into our water tank.
That's the basic description of the system. It's actually more involved because we're going to have pressure switches at the output of the pre-filters that will give a visual and audible indication when the filters are getting clogged. We'll also be using a TDS (total dissolved solids) meter at the output of the pressure vessels. This is made by Omega Instruments and will constantly monitor the salinity of the product water. If the level exceeds the set limit (which is adjustable) it sends a 12 vdc signal to illuminate a light on the control panel and also activate two solenoids that will cause the product water to be redirected overboard instead of into the tank. We'll also have a way of back-flushing the membranes to increase their useful life.
This is going to be a monstrous project, probably equal to the installation of the diesel heater. The RO membranes and housings are 40" long which is bigger than almost any space on the boat. Right now I'm planning to install them and the pre-filters up in the chain locker. The high pressure pump will be in a nearby compartment with the bow thruster. The feed pump will be mounted in the bilge area beneath the forward stateroom and the control panel will probably be mounted somewhere in the forward head. With all the gear located forward in the boat any noise from the system should be bearable if we're sitting out in the cockpit or down below in the salon. Since the system should be monitored while it's running we won't have it on while we're sleeping (duh).
Right now this is the plan. I hope to have all the parts assembled and installed by this Summer. This is a major component in our plan to sail and live independently, without having to rely on external resources. Well, other than the occasional refueling and maybe buying some food once in a while. We'll be able to make our own clean water in really useable quantities. We'll have the sun and the wind to make electricity and can fall back on using the genset if necessary. We can catch our meals from the oceans. We'll be able to get weather info and stay in contact from almost anywhere in the world using a single side band radio. We'll even be able to repair our own sails and canvas using our cool-man Sail Rite sewing machine. We'll have almost every angle covered. The only thing I can think of that we'll have to pull into port for.....I don't know how to make good rum.
