Water maker questions

[Bi111ion]

Having just completed my first non-stop passage of over 1000 NM on a bigger boat than my own nearly-40-footer I appreciate having a water maker for offshore cruising. I am new to reverse osmosis water makers and wonder what the current thinking is. On this larger boat, that needs electricity for winches too, they run a generator every day and make water from mains electricity. With that system the crew of 5 have the luxury of taking showers.

Currently don't have diesel generator, but solar and a towed generator, and a 150A alternator on the engine. I am planning to do longer passages and wonder if running a small water maker on solar and power is a reasonable alternative, running the water maker for long periods, or to fit a small (eg Fisher Panda) generator and a bigger water maker and run it for an hour a day.

If you run a generator to make water how does it work out in terms of litres of water made per litre of fuel?

 

[coopec]

Bi111ion

With a bit of luck I will be making the same decision as you soon.

Just did a search on "watermaker liter water per liter of fuel" and got some interesting links.

https://duckduckgo.com/?q=watermaker+liters+of+water+per+liter+of+fuel&t=h_&ia=web

https://www.google.com.au/search?so...j33i160k1j33i21k1j33i22i29i30k1.0.QjQEf07H7BY

I will definitely get back to you on this thread as I will be doing more research today. (Can't do anything on the yacht as it is blowing a gale)

It will be interesting to read OP comments on their experiences.

Clive

 

[sailaboutvic]

I build my own water maker, so at less two others on these forums ,
mine runs on 230v gen and will give me about 80/90 LPM .
I can say that sailing in the Med in over 25 years we never needed one we always found water some where , but getting older and carrying water isn’t doing my back any good , since building mine it’s made life so much better .
If you got room I would go for one or you can buy a 12v system but there not cheap

 

[KellysEye]

Don't buy a Fisher Panda they operate at 3.000rpm and have a life of 500 to 1,000 hours. The previous owner fitted a Lombardini 3,000rpm generator on our boat it committed suicide at 550 hours. The way to go is a 1,500rpm generator they have a normal diesel engine life of 8,000+ hours. I asked a number of repair shops in the Caribbean which of those they least had to repair first was Northern Lights closely followed by Westerbeke which we bought. Buying and fitting is not cheap ours was £6,000 14 years ago. I can't answer to water to fuel question because we had a 240v industrial water maker because they last longer and I never checked the fuel.

 

[shaunksb]

Having just completed my first non-stop passage of over 1000 NM on a bigger boat than my own nearly-40-footer I appreciate having a water maker for offshore cruising.

Have you considered Wet Wipes @ £1.65 for 40 sheets? Enough for a 15 day passage and quite compact to store.

Or failing that teach you crew how to have a boat shower or wash using a few litres not a few gallons.

Seriously, if you want a generator and water maker so that you can stand under a running shower every day you are talking about a big investment so think about it carefully.

If you do persist consider a fuel cell as opposed to a generator and look at running a water maker directly off the engine.

_____________________________

 

[sailaboutvic]

Don't buy a Fisher Panda they operate at 3.000rpm and have a life of 500 to 1,000 hours. The previous owner fitted a Lombardini 3,000rpm generator on our boat it committed suicide at 550 hours. The way to go is a 1,500rpm generator they have a normal diesel engine life of 8,000+ hours. I asked a number of repair shops in the Caribbean which of those they least had to repair first was Northern Lights closely followed by Westerbeke which we bought. Buying and fitting is not cheap ours was £6,000 14 years ago. I can't answer to water to fuel question because we had a 240v industrial water maker because they last longer and I never checked the fuel.

Fisher panda new gen are variable speed , I have one and it runs like a dream ,
The one I replace as been on the boat since 2001 .

 

[geem]

If you go down the 220v route with a generator you can use a Cat 247 pump directly driven from a 1.5kw motor. This pump running at 1450rpm will be able to make up to 250litres/hour if you run three 40" membranes in series. Our Perkins 4kva 3000rpm generator uses 1.1litres an hour at 50% load. Doing the maths I reckon it costs you about 2 pence a gallon if you pay 1.30/gallon for diesel. Or 227litres of water for one litre of diesel.
We currently have this set up but with only a 40" and a 21" membrane so we get 135l/hr here in the warm Caribbean waters.
So for every litre of fuel we use we make 121 litres of water. Hope this helps

 

[geem]

Don't buy a Fisher Panda they operate at 3.000rpm and have a life of 500 to 1,000 hours. The previous owner fitted a Lombardini 3,000rpm generator on our boat it committed suicide at 550 hours. The way to go is a 1,500rpm generator they have a normal diesel engine life of 8,000+ hours. I asked a number of repair shops in the Caribbean which of those they least had to repair first was Northern Lights closely followed by Westerbeke which we bought. Buying and fitting is not cheap ours was £6,000 14 years ago. I can't answer to water to fuel question because we had a 240v industrial water maker because they last longer and I never checked the fuel.

There is nothing wrong with 3000rpm generator sets in general. I cant comment on Fisher Panda but our Perkins 102-05 generator engine is as fitted to refrigerated containers. They run forever. Its the same block as used by Northern Lights three cylinder engines. Ours is the two cylinder version. Northern Lights run the three cylinder version at 1500rpm. Most of the parts between the engines are common. Ours probably wont last as long doing twice the revs but the last one was installed for 17 years before it dropped a valve. I had already bought a spare for £500 with just a few hours on it so should be good for another 17 years. This one has been running nicely for the last 18months and made us several tonnes of water

 

[jdc]

Some watermakers have lower pressure pumps which drive a more complex set of pistons in the water maker itself and tend to be more efficient (it's known as a Clark pump). Those made by Spectra for instance are like this. My one makes 22 litres per hour, drawing 9A at 12V.

I find that this is not a major factor in the electricity usage when offshore: Every 2 days we make about 50 litres (sailing 2-up that's enough we find). That's 25 / 22 * 9 = 10.2 AHr per day on average. The Fridge uses about 4A * 24 hrs = 100AHrs, the electronics etc adds another 50AHr and, if being used, the electric autopilot adds another 100AHr.

So the watermaker represents only 10 / 250 = 4% of the total electrical consumption. Not a reason to add a generator.

As for 12V versus 220V, I can't see the point of not using 12V. 9A is scarcely a high peak current and the flexibility of 12V is great: it works with all sources of power including the engine. This last is important: it's surprising how often one is running the engine for a few hours, and inevitably when we are we make water - it just becomes one of the routines.

Since fitting the watermaker I've not regretted it. We now go to sea without much in the tanks and make serious amounts of water in the first day or two of the voyage. This is because water is not often that good out of the tap when in tropical places whereas that from the watermaker tastes really good (at about 110 ppm TDS).

 

[geem]

Some watermakers have lower pressure pumps which drive a more complex set of pistons in the water maker itself and tend to be more efficient (it's known as a Clark pump). Those made by Spectra for instance are like this. My one makes 22 litres per hour, drawing 9A at 12V.

I find that this is not a major factor in the electricity usage when offshore: Every 2 days we make about 50 litres (sailing 2-up that's enough we find). That's 25 / 22 * 9 = 10.2 AHr per day on average. The Fridge uses about 4A * 24 hrs = 100AHrs, the electronics etc adds another 50AHr and, if being used, the electric autopilot adds another 100AHr.

So the watermaker represents only 10 / 250 = 4% of the total electrical consumption. Not a reason to add a generator.

As for 12V versus 220V, I can't see the point of not using 12V. 9A is scarcely a high peak current and the flexibility of 12V is great: it works with all sources of power including the engine. This last is important: it's surprising how often one is running the engine for a few hours, and inevitably when we are we make water - it just becomes one of the routines.

Since fitting the watermaker I've not regretted it. We now go to sea without much in the tanks and make serious amounts of water in the first day or two of the voyage. This is because water is not often that good out of the tap when in tropical places whereas that from the watermaker tastes really good (at about 110 ppm TDS).

I am not knocking 12v watermakers. Lots of cruisers have them and our previous boat had a 12v one. What I like about the 220v units is that fact they make so much water very quickly. Assuming we use the same amount of water as you, we run our watermaker 1/6 of the time you do. We never liked to leave our 12v watermaker running for a few hours without being onboard. We dont have that issue with a high output 220v watermaker. We also found that even though the 12v watermaker uses say 9amps/hour, whilst you are making water you are reducing your ability to charge your batteries. You need a very large solar array for this not to be an issue. Most of the people we know with 12v watermakers run their engine because of this issue at least some of the time unless you have unbroken sunshine and lots of solar.
For the OP, it is worth considering an engine driven watermaker. Connect this to three 40" membranes and make 250 litres/hr. The run time on your engine is tiny in the scale of things and a lot of the watermaking can be done when you are running the engine between places. Very simple systems without the complexity or cost of 12v motors, pumps, intensifiers that in my experience become unreliable with high hours. The high hours are inevitable due to the low output of these systems. Hope this helps your decision

 

[sailaboutvic]

Have you considered Wet Wipes @ £1.65 for 40 sheets? Enough for a 15 day passage and quite compact to store.

Or failing that teach you crew how to have a boat shower or wash using a few litres not a few gallons.

Seriously, if you want a generator and water maker so that you can stand under a running shower every day you are talking about a big investment so think about it carefully.

If you do persist consider a fuel cell as opposed to a generator and look at running a water maker directly off the engine.

_____________________________

Mine cost me £1000 to build my self , most of that was the cat pump , but you do need a gen set , some have made them out of pressure washer pump , you might find you could run them of a big inverters, I know my small pressure washer will run off our inverter .
The big question is how long will a pressure wast pump last four , one guy I met said his is four years old .

 

[jdc]

...What I like about the 220v units is that fact they make so much water very quickly. Assuming we use the same amount of water as you, we run our watermaker 1/6 of the time you do...

Electric motors are pretty much the same efficiency whether from 220V or 12V (or any other Voltage) so there's nothing about 220V versus 12 Volts which counts here: the watermaker membrane has no idea of the Voltage on the motor, just the pump pressure and capacity. The real question is 'what is the ideal size of watermaker for your needs?'

Some considerations I took into account when choosing mine:

1. You have to run it for a few minutes, say 5, each time you turn it on just to flush it - and that water is thrown away - so efficiency = (T - 5) / T where T is the time in minutes you run. Thus running for 60 mins is >90% efficient; 1/6th of an hour, ie 10 mins, is only 67% efficient.

2. You can't leave it more than 2 or 3 days between use or it gets smelly and needs pickling. Very careful flush with lots of fresh water can extend that a bit, but not a lot. We find that 7 days in the tropics is way too long and 3 days about the max.

3. Electrical consumption in Watts is directly proportional to volume flow-rate of water, hence 1kWHr produces a certain amount of water, which to first-order doesn't depend on the size of watermaker.

Putting these together, I suggest⁽¹⁾ that the optimum size of watermaker is one which in an hour or two can produce the volume you use in a couple of days. Bigger, and you need run it for a ridiculously short time so it's inefficient or you use it so infrequently that it goes smelly. Smaller, and you have to run it for long times. Not that this matters if it's powered from stored energy such as a battery system, but it negates the real advantage of using it while the engine or generator is on, which is probably only a couple of hours, and possibly means greater wear (although water makers, like diesels, thrive on use).

(1) I'd appreciate debate on this point - it's the conclusion I came to but I'm interested in other opinions (provided numerate and well argued).

 

[geem]

Electric motors are pretty much the same efficiency whether from 220V or 12V (or any other Voltage) so there's nothing about 220V versus 12 Volts which counts here: the watermaker membrane has no idea of the Voltage on the motor, just the pump pressure and capacity. The real question is 'what is the ideal size of watermaker for your needs?'

Some considerations I took into account when choosing mine:

1. You have to run it for a few minutes, say 5, each time you turn it on just to flush it - and that water is thrown away - so efficiency = (T - 5) / T where T is the time in minutes you run. Thus running for 60 mins is >90% efficient; 1/6th of an hour, ie 10 mins, is only 67% efficient.

2. You can't leave it more than 2 or 3 days between use or it gets smelly and needs pickling. Very careful flush with lots of fresh water can extend that a bit, but not a lot. We find that 7 days in the tropics is way too long and 3 days about the max.

3. Electrical consumption in Watts is directly proportional to volume flow-rate of water, hence 1kWHr produces a certain amount of water, which to first-order doesn't depend on the size of watermaker.

Putting these together, I suggest⁽¹⁾ that the optimum size of watermaker is one which in an hour or two can produce the volume you use in a couple of days. Bigger, and you need run it for a ridiculously short time so it's inefficient or you use it so infrequently that it goes smelly. Smaller, and you have to run it for long times. Not that this matters if it's powered from stored energy such as a battery system, but it negates the real advantage of using it while the engine or generator is on, which is probably only a couple of hours, and possibly means greater wear (although water makers, like diesels, thrive on use).

(1) I'd appreciate debate on this point - it's the conclusion I came to but I'm interested in other opinions (provided numerate and well argued).

We dont waste the water from that first five minutes. We fill our solar hot water heater and use it to shower. The TDS is a little high but its not salty for showering. Some automatic systems dont allow you to easily do this. We simply run off 10 litres initially which is good for two solar showers amd gets the TDS to where it needs to be to start filling the tank.
The problem with 12v motors is finding a reliable one. They seems to fail at a greater rate than 220v motors and they are expensive. We make 1200 litres of water per month for two living aboard. Our run time is less than 9 hours per month and will drop to about 5 hours once we get a new membrane for one of our housings. On a typical 12v system @9amps making 22lotres per hour the same consumption in a month needs 54hours of run time. Our robust 220v motor is lightly worked compared to the 12v motor.