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Old 08-10-2018, 02:14   #1
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size water maker 30L/ Gal 7.8 enough?

Hello,

Finally I put up a first post after reading this great forum for so many years.

We are fulltime cruisers from the last 3 months, after years of planning. We sailed from the Netherlands to Portugal, Lagos now and are completing the ship now for ocean cruising for many years to come. Anchoring should become the standard.

One of our choices is a what size water maker. We have a 43ft ship and are with two people. We think about a Capacity: 30 lit/h - Gal/h 7.8 or double of that 54lit/h about 15Gal/h.

Even with 43ft, space is a factor as we do not have a typical cruiser and need to be smart. So for space we would favor 30L, for water results of course 54L/ 60L of course. (We probably would go for a low energy consumption water maker)

We would love to here opinions of people who use 30 lit/ Gal/ 7.8 water makers. Is it big enough or just not realistic/a lot of hassle to get enough water? Or it takes to long to get enough water. I assume it needs to be run daily. Would you make the same choice if you buy a new water maker?

I'm probably not the first to ask the question and have read numerous post on this forum but stil I thought, why not ask the question directly.

Kind regards,

Martin
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Old 08-10-2018, 04:21   #2
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Re: size water maker 30L/ Gal 7.8 enough?

Greetings and welcome aboard the CF, Martin.
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Old 08-10-2018, 04:36   #3
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Re: size water maker 30L/ Gal 7.8 enough?

We have a family of four and use around 5-10 gallons a day on average, though are very careful with water. Unless we use the washer/dryer - that takes a bunch (something like 10 gallons on its own but Iíve not yet measured it yet; we got it this year). We are also putting on a watermaker and know that if we could have the luxury we would easily double our usage (longer showers, less careful dish washing, etc). We went with a Newport 400c - 17 gal/64 liters per hour and runs on 12v (we have solar and wind).

We figure running one hour per day will be perfect giving us almost twice our conservative water usage, and when doing laundry would run it then as well (genset running anyway!)
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Old 08-10-2018, 04:43   #4
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Re: size water maker 30L/ Gal 7.8 enough?

Check out Schenker water makers, we have the smallest one with 30 liters an hr and are very happy with. With energy recovery so it needs not a lot of power and can easily run with solar only.
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Old 08-10-2018, 06:07   #5
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Re: size water maker 30L/ Gal 7.8 enough?

These days we are using about 25L of water per person. This includes all our water use, showers (everyday), dishes, cleaning, WASHING MACHINE, drinking.

When we first started cruising we used about 1/2 this amount. However as the years have ticked by, we wanted more comfort. Since we had a high output watermaker (120L/hour), it was nothing to just make more water. We make water every 3 days (for about 2.5 hours). Unless we are planning an offshore passage, we drain our tanks completely before making more water. This way we always have very fresh water.

So yes the 30L/hour unit would probably do just fine. However, you will probably need to run it at least 1 hour every day (even if you are frugal).
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Old 08-10-2018, 06:12   #6
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Re: size water maker 30L/ Gal 7.8 enough?

If you are already running a large ICE power source many hours per week, then go with a **higher** L/hr unit, sized to take advantage of "excess" power already being produced, that is, not interfering with existing loads' functions. Energy efficiency becomes a low priority, and you will only run it a few hours maybe twice a week.

If you live on the hook for weeks in silence, and want to run off solar / batteries, then focus on not just energy efficiency, but **quiet** operation, since it will need to run many hours per week, perhaps almost daily.

I think in your case the former approach applies.
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Old 08-10-2018, 09:23   #7
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Re: size water maker 30L/ Gal 7.8 enough?

The energy requirements to make 15 gph won't change appreciably from 7.8 gph. If there is any way you can make the membrane fit, choose the larger capacity. Run it frequently to keep your tanks full. It's hard to have too much water in your tanks, especially on an ocean passage when your watermaker fails! You'll thank yourself many times over vs. castigating yourself for going small/being cheap!
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Old 08-10-2018, 09:28   #8
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Re: size water maker 30L/ Gal 7.8 enough?

Martin,

From the capacity you mentioned, I'm guessing you are only considering DC powered watermakers [12 or 24 volt DC.]

We have a 12V DC Spectra [older model Santa Cruz]. It has 2 independently switched raw water feed pumps. [run one or the other, or both]

The second feed pump increases production and provides for hot back-up. In our cooler water each raw pump produces about 23 l/hr [6 gal/hr] We always run both [e.g., 46 l/hr; 12 gal/hr] but can easily get by with one. Regardless, our unit consistently produces 1 gallon of water for each 12V DC amp-hour consumed. Very efficient.

My point is the difference between the two capacities you are inquiring about is nothing more than an extra raw water feed pump— which is likely standard on current Spectra models. [My conjecture as I have not had the need to replace our 17 year old unit yet...]

Regarding adequacy; we are two adults [with occasional guests] cruising full time. We don't take careful water conservation measures except to only use what we need. [We even rinse the anchor chain and deck with fresh water– after using raw water to blast off the mud and crud.]

We run the watermaker on average every 5-7 days, all day [e.g., 12+ hours. We understand Spectra watermakers prefer long run times instead of multiple short runs...] That is usually laundry day as well, so we are consuming extra as well as filling our tanks.

Even if we were down to one feed pump [e.g., 23 l/hr] it would be very adequate. The only difference would be longer runtimes.

In case this is helpful.

Best wishes deciding what is best for your needs.

Cheers, and welcome to the forum!

Bill
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Old 08-10-2018, 09:42   #9
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Re: size water maker 30L/ Gal 7.8 enough?

svSnow
Only you can answer the how much water do we need question. Now that you are out for 3 months you should have some feel for how much you use. When you get a watermaker your use will typically increase some.
If you are using an efficient 12v unit like a Spectra you will get plenty of water with the 7gph type units for two. Going to the 15gph will just make things more convienant for little more cost and add some redundancy. The install size is not much different.
There's some advice posted on this thread which seems to come from people who have not cruised with a watermaker. Firstly the sound issue is not an issue. You don't run a watermaker under your bunk when you are trying to sleep. And comparing it to the noise and heat of a generator just pales. Often the tradewinds howling in the rigging is louder than our watermaker.
You don't want to run a watermaker an hour a day because each use requires a freshwater flush that eats up 30 mins of running.
Doubling the output of your watermaker will double the power used. There's no free lunch.
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Old 08-10-2018, 10:14   #10
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Re: size water maker 30L/ Gal 7.8 enough?

It depends on how you like to power up the watermaker. If you have a generator and do already use it for charging batteries, then at the same time make your water and you want the larger capacity watermaker. On the other hand if you are without generator and operate mostly solar, and don't want to idle your engine too much, or if you do lots of powering from place to place so you can run the engine several hours each week, then the smaller capacity watermaker may make sense.

So just figure out how much time you will have extra power from generator or engine available during an average week. Then compare that to your known water usage (you cruise a lot so you must already know your needs). Get the capacity watermaker that will supply your weekly needs during that time when you have excess power available.
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Old 08-10-2018, 10:45   #11
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Re: size water maker 30L/ Gal 7.8 enough?

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Originally Posted by Paul L View Post
the sound issue is not an issue. You don't run a watermaker under your bunk when you are trying to sleep. And comparing it to the noise and heat of a generator just pales. Often the tradewinds howling in the rigging is louder than our watermaker.
You don't want to run a watermaker an hour a day because each use requires a freshwater flush that eats up 30 mins of running.
Doubling the output of your watermaker will double the power used. There's no free lunch.
I agree, the sound really isn't an issue unless you plan to run the unit at night. The high pressure pump (depending on the design) does make some noise, but as Paul points out, wind noise often drowns it out! Regarding running for an hour a day, you need about 1 gallon to flush the membrane, so only if you're making 2 gph will the flush consume 30 min of run time. Make 15 gph and you're only "wasting" about 4 min of run time. But, in general, the longer your run times before flushing, the more efficient your system is. And finally, actually, while not a "free lunch", there is more efficiency with a larger watermaker. A pump that produces twice as many gpm doesn't use double the power, it just goes up maybe 40% or so. Not a free lunch by any means, but more bang for the buck!
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Old 08-10-2018, 11:03   #12
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Re: size water maker 30L/ Gal 7.8 enough?

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Originally Posted by mvmojo View Post
...... And finally, actually, while not a "free lunch", there is more efficiency with a larger watermaker. A pump that produces twice as many gpm doesn't use double the power, it just goes up maybe 40% or so. Not a free lunch by any means, but more bang for the buck!
A Spectra Cape Horn offers the ability to run at both 7-8gph or 15gph. The current draw +/- a little doubles between the two modes, and this is one of the most efficient watermaker available anywhere.
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Old 08-10-2018, 11:59   #13
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Re: size water maker 30L/ Gal 7.8 enough?

If you have been cruising for 3 months you should already have a really good idea how much water you use per day.

For the health of the membranes, the more often you run them, the better. So getting one greatly oversized and planning to run it once a week is a bad idea. For lots of reasons, small water makers make a lot more sense than big ones.

We are two people on a 52 foot boat, and have all the water we would ever want from a 40 liter per hour model run for about an hour every 2nd or third day when we run the genset. If I was starting from scratch, and could pick things for myself, I'd likely select a unit half that size, and run it every day from the solar panel output.

We have 1000 liters of tank capacity, and just keep it full all the time. If we are in full "conservation mode" 1000 liters would last us about 3 months. If we are in "profligate mode" our usage would be about double that.

So for two people we figure between 10 and 20 liters a day. Some use a bit less, others use a LOT more.
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Old 08-10-2018, 12:46   #14
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Re: size water maker 30L/ Gal 7.8 enough?

For another point of view, we (2 persons, 43' boat, with occasional guests) bought and installed a 30gal/hr watermaker 4 years ago. We run the genset to provide power, and generally refill when we're down about 2/3's of capacity...we keep 1 of our 4 tanks full and isolated for an emerg backup source. We run the machine for about 2 hrs to refill the tanks, and make water about every 4th day, plus or minus. Anything smaller means we're making water for a long time each time, and likely would need to run it way more often. We found a place to install the double membranes, under the fwd berth, and are very happy with our choice of watermaker. Our boat is set up to run the genset every day, so making water every day would not be a big deal.....but it's really nice not to need to run the watermaker every day.
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Old 08-10-2018, 13:03   #15
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Re: size water maker 30L/ Gal 7.8 enough?

Choosing a watermaker is a different process with each individual boat. I call it my Goldilocks approach. You can buy a watermaker that is too small for your needs, and don't be fooled, you can buy a watermaker that is too large for your needs as well. As mentioned above, the first thing you need to know, and this is very important, is what your average daily consumption is for each person on board. I like to size a watermaker that can roughly produce in one hour what your daily consumption is. This way you are not running your watermaker every day for hours, if you are then it's way too anemic for your needs. Usually, on an average modest sailboat, I will see people use 5-6gallons per day per person. So taking into account that you are on average two people on board a watermaker making 10-12 gallons per hour is just about right. This way instead of running your watermaker every day for an hour to keep up with use you may only run it every three days for 3-4 hrs. As mentioned above you'll need to flush the system after each use using fresh water, and this amount is usually in the four gallons range to really flush the system properly. This leaves the other 2.5 days of not running your system. This way when you do have guests or you are just wanting the occasional larger amounts of water, running your watermaker every other day for twice as long will give you that. These are "BOAT" pieces of equipment. Always take into consideration wear and tear. A watermaker run every day for hours, obviously won't last nearly as long as a watermaker run every second or third day. Not sure what 6-7gph watermaker you are looking at, but a Spectra 200T would fit this. But usually if a customer is looking at this particular watermaker model it is easy to up sell them to the Cape Horn Extreme330. For about $700 more it's like getting two 200T's in one and very well worth the cost increase. The energy use is basically the same. You want to measure the Watts used to make one gallon of fresh water. The 200T uses 14.5 Watts per gallon made, the Cape Horn Extrem uses 16 Watts per gallon made (with both pumps running) and with either pump running alone it uses 13.5 Watts per gallon made. This unit is the only watermaker made with two feed pumps, you can operate the system with both pumps at 14gph or with either pump alone making 7gph. This gives you great redundancy if one pump fails you are not out a watermaker. Plus it's the easiest pump in the watermaker world to replace, three screws, two 5/8" hoses and two wires. Those of you with the older Santa Cruz model 380 might disagree with the ease of replacement, one of the reasons we haven't offered the Santa Cruz for well over a decade. A spare pump head on board is always a great idea. The Cape Horn Extreme IS the worlds most energy efficient watermaker. While I never disparage any other watermaker company, I'm a bit shy of these Mutant Ninga Turtle Spectra knock offs.
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