Manual Water Maker

I read everywhere that electrical water makers are not the most reliable component on a boat so I googled for a manual water maker.

I found one, it is small and have a turn knob with thread to screw the plunger in to achieve the high pressure required to force the water through the osmoses filter.

I also phone someone I know who sells water purifying systems. He says the filters that are capable of filtering sea water can be washed or rinsed and re-used.

I was wondering how practical it would be to make a similar hand water maker but with a bit larger capacity. Carrying large quantities of water aboard accounts for a lot of weight. It would be nice if one have a practical way of making fresh water without spending hours and have it very reliable as well.

 

Fanie,

In my experience the reliability of watermakers is due to the filters not the mechanical components. So while a hand operated water maker may operate independent of the boat systems, they really don't solve the reliability problem. Add to this the amount of pressure reverse osmosis systems need to operate efficently (around 850 psi) and there just isn't a viable option to mechanical makers, excepting very low volume uses like aboard life rafts.

For instance the Horizon system makes 150 gallons a day, weights 70lbs and consumes less than 25 amps at 12V. This is a pretty small machine but lets take a look at hand operated options

Now taking a look at the PUR Survivor 06 manual watermaker, and while it only weights 2.5 pounds, assuming you could pump 24 hours a day, 40 strokes/minute, you would produce about 48 pints, or 6 gallons a day. Now I have real doubt that anyone could maintain 40 strokes/minutes for an hour but assuming it is possible, relying on this for drinking water means that every person on board must spend 4 hours a day pumping just to produce the 1 gallon they will need.

My advice is unless you are only worried about survival situations go with a mechanical unit, and be sure to follow the recomendations on filter maintenance, because the hand operated ones are next to useless.

As for makeing a larger unit... I think the problem is the amount of mechanical input it takes to produce one gallon is going to be the same, regardless of the number of strokes used. And it just isn't realistic to think a person can apply this amount of work.

 

Seems only married men can operate the manual unit then

Sorry, couldn't resist.

What you said is about what I expected. If the problem is usually with the filters, one could maybe have a spare.

If there is a way to take much less water one save a lot of weight. A couple of people use quite a bit of water, some even drink it.

I was hoping someone could come up with another sensable and less expensive method of making fresh water.

 

Well you could look at evaporation water makers, which take no power but also produce limited volumes. I guess just like solor cells a large enough array would do the trick. Though I am guessing a large solar array would work better driving a powered water maker.

As for spare filters, we always carried 2-3 extra onboard at all times. Not that we ever needed this many, but because it was a real pain getting them down island.

 

Right Stumble.
Under North African sun a commercial installation can produce about 200ccm per hr. m², thats about half a Gallon day. On a boat I would reckon max. half of that. So, evaporation does´nt sound good. On the other hand PV arrays produce about 100Whr. m² thats not the jackpot either.

The main prob. with watermakers aboard is the lack of regular useage. The more they work, the better. And of course if you are bluewater sailing you have a eye on them daily and replace filters, spares and membranes regularely. The average boater does´nt.
I install mainly Echo²tec by the way, very reliable and reasonable priced.

Regards
Richard

 

I don't think the idea is a huge fountain of water, but one should be able to get enough for drinking at the very least, and a few other activities of course.

So if I hear right, the electric water maker is about the only sensable item to have, and you can have an emergy mechanical one for if all else fails.




Can one cook food with sea water ? I've bever tried it.

 

Regards
Richard

 

I don't have a watermaker on my boat (we're on freshwater lakes, so no need for one). I do tend to agree with Stumble and Apex that you'd be hard-pressed to find a manual unit that's really suitable for use as a main watermaker.

However... that's not to say it's impossible to make one. Just tossing ideas out here, but what would happen if one were to hook a pressure washer pump up to the flywheel of a stationary bike? There's your 1200 psi or whatever, in a much more powerful configuration than those little survival pumps. A two-horse Honda can give two or three gallons a minute with one of these pumps, so a person (say 1/4 hp) ought to be able to get a gallon of water at 1000+ psi every four minutes or so.

 

There are some low pressure system on the market too, just do´nt have access to my database here (Aegean sea).

 

Marsh,

I doubt that the hand operated pumps could take the strain of being hooked up to an engine, they are really pretty flimsy items, and while this may work, it seems like a lot of trouble to go through when modern water makers are actually pretty efficient, and run off of 12V systems. Assuming you don't have a generator they may demand running the engine every couple of days, but that is pretty common anyway.

Apex,

I don't have any experience with the low pressure systems, though it does look like they use less power while running, but I couldn't find numbers to let me calculate power consumed/gallon produced. If you have those stashed somewhere I would love to see the comparisons.

 

I've used a few small backpacking filters, one of which claimed to be suitable for use in salt water.

The biggest flaw in them? They are small and compact enough that you can carry them in your pocket. Why is this a flaw? Because it means you provide all the power with next to no mechanical advantage.

On a boat you should be able to find space for a 3 foot long handle to attach to a short stroke pump to provide pressure. While it isn't perfect or easy, having a larger unit that lets you use more mechanical advantage should mean you can pump easier, and therefore pump longer. You're not likely to get enough to take a hot shower every day, but you should be able to produce enough water with the right setup to keep yourself alive around all your other duties of the day.

However I would personally go for a dual system. One engine based unit, and a backup human powered unit for if the first breaks.

 

Luckless the problem still comes down to capacity. The filters can only desalinate so much water in so much time. Overflowing the membranes won't speed up water production more than marginally, but will reduce the lifespan of the other components in the system. With the limited volume production I just can't see these an an option except when in a liferaft, since who in their right mind is going to want to spend four hours a day pumping something to have drinking water? Sure in a survival situation it is worth it, but otherwise not a chance.

 

Have you ever filled a bike tire with one of those little hand pumps that is shorter than your forearm? You can't get very much air flow or pressure through one. Now compare it to a large stand up unit with a long lever, now you can achieve higher pressures, or far more volume transfer in a given time.

Using the filters is still a function of volume and pressure, so if you are exceeding the volume/pressure for the size of the filter used,... then get a bigger filter.

 

We should´nt mix up the terms here! The filters are no prob. the membranes are. And you cannot operate a RO system on a pressure you like! So, that was not correct.

Stumble
I am on the water at present, I do´nt have even a bookmarked net addy to provide. And I doubt I have the data to compare, that niche was never important for me.


Regards
Richard

 

You are right increasing the filter size would increase the desalination capacity of the system, so lets look at a possible system.

System and assumptions:
-Instead of a hand pump we are going to use a stationary bike since leg power is easier to output for a long period of time than using your arms.
- Now the generally accepted maximum output for an olympic caliber cyclist is about 2/3 horsepower so we will use this as out base, and lets assume they could maintain this level of output infinitely.


2/3 of a horsepower is about the same output rating as the engine on the Plastimo low pressure water maker system uses. So we could replace the motor on the water maker and put in place a stationary bike with a reduction gear to get the RPM we would need. Now this unit makes about 15L/hour (just shy of 4 US gallons/hour), so it would be possible to do this type on conversion and get rid of the electrical motor, though now you do need somewhere to store the stationary bike.

But this does nothing to address the problem of reliability in water makers, since almost all of the problems are in the membranes, not the motor. However this does reduce the power load of the boat, which is always a good thing. Plus it gets you some exercise. Personally I still don't want to do it, but the numbers at least indicate it is theoretically possible.





To be fair, when I started the math I expected it to be impossible to make enough water by pedaling to justify the hassle. God I hate when I prove myself wrong.