Which Watermaker To Choose

[goboatingnow]

Originally Posted by GrowleyMonster

Anybody have any good links or sources of info for DIY watermakers? Honestly, I think I could do well with a capacity of a pint an hour. I would rather have a very small electrical load constantly or during the day when solar is feasible than some big honking 20GPH thing running just a few minutes a day. Seriously... at sea I use about a gallon a day. Even in the marina, with free shore water, I don't use 10 gallons a day. Is the economy of scale such that a micro-watermaker isn't practical? The smallest one I see is the Katadyn. Or the even smaller hand powered one.

A search here and google will unearth several. I built one , its not really practical to build what you suggest from common RO equipment. The membrane has a minimum flow requirement . The most common being Dows filmtec SW 30-2540 membrane

Dave

[GrowleyMonster]

Originally Posted by goboatingnow

A search here and google will unearth several. I built one , its not really practical to build what you suggest from common RO equipment. The membrane has a minimum flow requirement . The most common being Dows filmtec SW 30-2540 membrane

Dave

Wouldnt the minimum total flow rate be less with a smaller membrane area?

Is there a minimum pressure as well, or just whatever it takes to deliver the right flow?

[wolfenzee]

My personal view point on the matter is that all resources should be used as conservatively as possible without causing discomfort. If you get in the habit of using excessive amounts of any resource, then/when something goes wrong you will not be prepared to handle it.

[downunder]

Originally Posted by wolfenzee

My personal view point on the matter is that all resources should be used as conservatively as possible without causing discomfort. If you get in the habit of using excessive amounts of any resource, then/when something goes wrong you will not be prepared to handle it.

Few vessels and particually earlier designs had water capture or adequate tankage built in to designs to agument or as a backup or design element for long distance cruising. Wolf, do you capture water or rely on lugging jugs.

Why? Room/capacity on small vessels and majority of vessels particually smaller were not originally designed from the get go for long distance cruising. Most are used locally for day sailing/coastal cruising. Just read the blogs of cruisers going further afield. Always seem to be chasing water/fuel/washing facilities. This is reality with many vessels and an issue with the many who are considering cruising with older or ex- charter production vessels. Just reality.

Some vessels built from the start for long distance crusing such as Dashew as one example changed that. If you read his books his view changed over time as yours may also. Very easy to do in the design stage of a vessel, particually a catamaran cruising the tropics. A watermaker is just another method of suplementing water supply and possibly one of the most chosen upgrades for long distance cruisers thesedays who live on their vessel and do not wish to camp as they go.

We should always respect all choices. This thread is to discuss which watermaker to choose for those who choice is to buy/build a watermaker. Thats not to say you have not raised some very good points to consider and we often agree to disagree.

Cheers.

[goboatingnow]

Originally Posted by GrowleyMonster

Wouldnt the minimum total flow rate be less with a smaller membrane area?

Is there a minimum pressure as well, or just whatever it takes to deliver the right flow?

I can't say, there isn't any in common production, it must be as you say

Dave

[philocat]

Originally Posted by goboatingnow

....I built one.... its not really practical to build what you suggest from common RO equipment. The membrane has a minimum flow requirement . The most common being Dows filmtec SW 30-2540 membrane

Dave

Similar to G's post this minimum flow requirement was also troubling me. If this could be achieved by other means - say an additional secondary loop - and running the HP pump at slightly below normal pressure then presumably you could then use the larger common membranes to suit a low power budget.

Perhaps similar to the attached sketch. The transfer circuit that achieves energy efficiency could also be run at a rate to satisfy the min membrane flow [cleaning] rate but higher than needed to keep salinity on the membrane within acceptable limits. Obviously needs power to do this and would decrease overall efficiency a little but as a trade off for using standard components. The HP pump feed (which consumes the bulk of power) would be configured/sized to match available power.

Whether its worth all the trouble I'll leave to others but for the few extra components I'd say it should not add that much extra to overall cost at least for the DIY, and probably still less than the proprietary systems.. Then you have a system using cheaper std components, flexibility to either run run high /low output and with good efficiency at least for the important low power case.

[daddle]

Originally Posted by GrowleyMonster

Wouldnt the minimum total flow rate be less with a smaller membrane area?

Is there a minimum pressure as well, or just whatever it takes to deliver the right flow?

Interestingly, the salinity goes up as the pressure goes down. To get lower flow it is necessary to use lower pressure. So a low flow unit would need a suitable small membrane - which does not seem to be readily available.

My preference, too, would be a 1gph unit that runs quietly while the sun shines.

[John Galt]

Here's my Katadyn 80E ready to install. They claim 3.4 G an hour on 12V. At 6 amps I'll shut the freezer fridge off and run it an hour or two in the morning.
Not a fan of the Jerry Jug shuffle.

[wolfenzee]

Originally Posted by downunder

Few vessels and particually earlier designs had water capture or adequate tankage built in to designs to agument or as a backup or design element for long distance cruising. Wolf, do you capture water or rely on lugging jugs.

Why? Room/capacity on small vessels and majority of vessels particually smaller were not originally designed from the get go for long distance cruising. Most are used locally for day sailing/coastal cruising. Just read the blogs of cruisers going further afield. Always seem to be chasing water/fuel/washing facilities. This is reality with many vessels and an issue with the many who are considering cruising with older or ex- charter production vessels. Just reality.

Some vessels built from the start for long distance crusing such as Dashew as one example changed that. If you read his books his view changed over time as yours may also. Very easy to do in the design stage of a vessel, particually a catamaran cruising the tropics. A watermaker is just another method of suplementing water supply and possibly one of the most chosen upgrades for long distance cruisers thesedays who live on their vessel and do not wish to camp as they go.

We should always respect all choices. This thread is to discuss which watermaker to choose for those who choice is to buy/build a watermaker. Thats not to say you have not raised some very good points to consider and we often agree to disagree.

Cheers.

Quite simply because most boats are designed and built with the intention of being used for weekend coastal cruising. Almost any boat that is to be used for long passage making needs a tremendous amount of modification. I can't think of any boat designed to have a water capture system and/or extra tankage and/or extra capacity for anything else it is at best something that is decided on during construction, but useually comes much further down the road. The second owner of my boat doubled the design water storage to 50gal (with an additional 45 in three 15gal portable containers) and it wasn't until after 40,000nm and 4 owners that water catchment was even considered. There are some pretty imaginative methods of water catchment, I met some circumnavigation that had their bimini set up so in a moments notice it transformed into a very effective water catchment...someone suggested I take advantage of my spacious decks and high bulkwarks....just use your imagination

[Matt Johnson]

I just love the fact that I'm taking my energy from the sun, turning a pump, and making fresh water out of salt. Pretty high tech, but still something primitive and natural about it.

[philocat]

Originally Posted by daddle

Interestingly, the salinity goes up as the pressure goes down. To get lower flow it is necessary to use lower pressure. So a low flow unit would need a suitable small membrane - which does not seem to be readily available.

My preference, too, would be a 1gph unit that runs quietly while the sun shines.

There is output flow and what I understand is a flow across the membrane - two different things. I didnt know that low (output?) flow -> higher salinity so that says a lot about what I know. Can anybody shed any wisdom?

[downunder]

There are increasing numbers of designers (mainly catamarans) recently who are building simple/efficient water catchment and easily 1000w solar panels into the designs without having to retrofit brackets. Cats setup for the tropics using the hardtop cockpit and saloon roofs have real advantages, here. The production builders are just starting to consider fitting solar as an option. I think Nautitech, is one of the smaller production cat builders who have incorporated water catchment into their designs. Simple really, more difficult on a monohull.

Quote: "The Nautitech 442 is an excellent choice for sailors with the intention of going on a world tour. Its new roof with a water recovery system feeding a separate water tank increases autonomy on board.

The optional solar panels allow one to set off without having to worry about getting back to harbour."

""

[downunder]

Originally Posted by wolfenzee

Quite simply because most boats are designed and built with the intention of being used for weekend coastal cruising. Almost any boat that is to be used for long passage making needs a tremendous amount of modification. I can't think of any boat designed to have a water capture system and/or extra tankage and/or extra capacity for anything else it is at best something that is decided on during construction, but useually comes much further down the road. The second owner of my boat doubled the design water storage to 50gal (with an additional 45 in three 15gal portable containers) and it wasn't until after 40,000nm and 4 owners that water catchment was even considered. There are some pretty imaginative methods of water catchment, I met some circumnavigation that had their bimini set up so in a moments notice it transformed into a very effective water catchment...someone suggested I take advantage of my spacious decks and high bulkwarks....just use your imagination

I did make that point.

There are increasing numbers of designers (mainly catamarans) recently who are building simple/efficient water catchment and easily 1000w solar panels into the designs without having to retrofit brackets. Cats setup for the tropics using the hardtop cockpit and saloon roofs have real advantages, here. The production builders are just now starting to consider fitting solar as an option. I think Nautitech, is one of the smaller production cat builders who have incorporated water catchment into their designs. Simple really, more difficult on a monohull.

Quote: "The Nautitech 442 is an excellent choice for sailors with the intention of going on a world tour. Its new roof with a water recovery system feeding a separate water tank increases autonomy on board.

The optional solar panels allow one to set off without having to worry about getting back to harbour."

[carstenb]

As the OP, I'll chime in again. A while ago, Surfer Girl suggested that lugging large jerry cans of water was the only fitting and proper way to have water on an RTW. I'll repeat myself, just noone misunderstands.

If necessary, I'll lug water. But with todays technology, that shouldn't be necessary. I plan on having a raincatchment system (rigged from the boom and able to send the water into either one of my tanks.

I will install a watermaker. In my ideal world, the watermaker is small, using relatively little juice. This means it runs most of the day (using less juice than my solar normally produces). which also means I want something quiet.

Unfortunately, ya can't always get what ya want - so you have to make do with what ya need (love old stones).

any of the three variables:
production capacity
noise
juice usage
can be traded off as far as I'm concerned, I don't want to trade off all three.

While not decided yet, I'm leaning towards a 20-30 liter per hour system. these use low wattage so my solar should be able to keep up with it (in the tropics)

[mcarling]

Originally Posted by otya

There is output flow and what I understand is a flow across the membrane - two different things. I didnt know that low (output?) flow -> higher salinity so that says a lot about what I know. Can anybody shed any wisdom?

Understanding osmosis is definitely necessary and probably sufficient to understand why salinity decreases as flow increases.