Watermaker or not?

We had a water-maker on our last boat but do not have one on our current. I think the decision of whether or not to get one hinges on a number of issues some of which have already been covered like lifestyle and budget. I would add to the debate the issue of size of tanks. Our last boat’s were relatively small so a water-maker was higher up the list, Our current boat carries lots of water and so the decision to buy a water-maker is far less pressing. Another issue is location. Our tanks may not be sufficient for some parts of the world and if/when we get to them we may fit a water-maker but they are sufficient for the eastern Atlantic and the med so currently we don’t need one. We can also carry lots of fuel if only we could afford it, so we might convert one of the fuel tanks to water. This would give us a further 750 lts capacity. If/when we add a water-maker I would not again go down the route of genny and large output water-maker (the set up we had before). I would prefer either solar panels and low output water-maker or main engine and a low volume unit then (depending on the combination) whenever the sun shone or the engine was running we would be making water (which would help with the regular use requirement).

We are able to enjoy a big boat because she is very basic and right now we don’t need another thing to maintain but these things are relative.
 
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Thank you all for the various thoughts. I think a spell at Southampton with a tape measure might be the next step. Fair winds all.

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David

I have returned from my wanderings and will be selling Dufours at Southampton, but please feel free to come by and pick my brains on our watermaker.

I shall be on or around berth 360, right hand side of the pontoons as you look out at the pontoons from the show.

John
 
Watermakers, additional question

As a lot of watermaker owners seem to have gathered here, may I ask a question: is it possible to use it in tropical rivers, or tropical tidal rivers with saltyish water, where there is often a suspension of lime, silt, very fine mud or sand, or possibly mercury and other nasties ?

I asked a couple of manufacturers a few years ago and they said no, but as the related technology seems to evolve quite rapidly... ever used yours in dirty water ?


thank you
 
Re: Watermakers, additional question

You can use them in 'muddy/silty' waters, we've done that many times including rivers, you just need to change the main prefilter more often. If there is anything nasty in the water (chemicals, sewage etc, look at what is upstream) then no. Although I believe there are now UV and other technologies that can take that sort of stuff out i.e. more things to go wrong.
 
Re: Watermakers, additional question

Yes, we use ours in mud, silt and algae conditions also. We drink our watermaker water (further filtered with a General Ecology filter) and we just don't fancy making water where there is likely sewage contamination. In an anchorage, I generally wait a day until I can see when the current is not taking waste from other boats in our direction.

Spectra make the point that even oil is not a problem as it lies on the surface unless the surface is whipped-up (don't forget speedboats).

We are very careful indeed in Spanish waters where often you only need your nostrils to confirm that sewage is to be found along the beach. The biological tests posted up on beaches are, I suspect, taken out of season or fraudulent (just as likely, actually).

We use our holding tank for all solids when in an anchorage but not everyone does.
 
Re: Watermakers, additional question

Roberto, I have just read your post more carefully having replied to Kelly's Eye, earlier. Membranes are designed for different purposes and varying salinity. The market for yacht desalinators is tiny compared with the market for industrial reverse osmosis systems so ours are just a tiny subset of the total. If you look at the membrane manufacturer's data sheets you will see that they target different applications - some for fresh city water down to very salty Mediterranean and Tropical water. Some oceans are more salty than others - checkout Plimsoll line on the wiki at http://en.wikipedia.org/wiki/Waterline

OK, so firstly one chooses the correct membrane then one has to find a pump with the right characteristics - and that's a more contentious issue. I'm leaving out the issue of source of power - ac/dc/solar/generators - but we can come back to that if you need. Some pumps (in their operating range) can be considered as producing a static head in Bars. They are usually electric but can be run from an engine direct. The problem with this approach is that the pressure does not vary as the salinity varies yet, for a given product output, you need to increase the pressure as the salinity increases. If you should happen to run these in fresh or brackish water the membrane pass larger than intended quantities of product unless you have a flow regulator. Maybe this would damage the membrane - it is outside the specification, for sure.

There is another type of system - patented - called a Clark pump which is offered by Spectra. The motive force for the system is provided by one or two low pressure ParMax pumps just like ordinary domestic water pumps. The process is a direct analogy of the footbrake on an old-fashioned car without servos.... you put your foot on the pedal and the ratio of the diameters of the master and slave cylinders gives a pressure increase, allowing a little old lady to stop several tonnes of speeding metal with ease. With this system, variations in pressure across the membrane do not have such a big effect on the driving pumps so they produce an almost constant flow. The mechanics of the system (look at Spectra's website for the details) ensure that a fairly accurate proportion of flow water results in product. So, whether you are in fresh, brackish or very salty water the Spectra has a fairly constant flow. My reading of the membrane specs is that Spectra are possibly working outside the designed parameters though to be fair, Spectra sell their membranes as a proprietary item and I have no means of accessing the data - I am guessing and making assumptions that are possibly wrong. Nevertheless, the shutdown and pickling procedure for the Spectra includes running what is essentially fresh water through the system. Mine has been running for six years with no problems and no reduction in output due to the membrane so you can be confident that with a Spectra you will be OK. Confirm that with the Spectra people, of course.
 
Re: Watermakers, additional question

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Some pumps (in their operating range) can be considered as producing a static head in Bars. They are usually electric but can be run from an engine direct. The problem with this approach is that the pressure does not vary as the salinity varies yet, for a given product output, you need to increase the pressure as the salinity increases. If you should happen to run these in fresh or brackish water the membrane pass larger than intended quantities of product unless you have a flow regulator. Maybe this would damage the membrane - it is outside the specification, for sure.


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As salinity decreases we simply adjust the pump pressure downward to maintain the normal product water flow. If you don't reduce the flow it doesn't damage the membrane but it does prematurely foul it, thus requiring cleaning. As I've mentioned ours is a 240v HRO, made of standard parts, other water makers may be different.
 
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