Help Me Choose a New R/O

[Pelagic]

Hi Guys,
I have read all your posts on water makers, (including SSCA) with often conflicting opinions but sensible reasoning.

As advised, choosing one that is right for me is the starting point and here is where I want to think out loud and get more up to date knowledge than I possess on whether there are any real benefits to investing in a new modern unit or sticking with my old.

My Status:

• We live aboard in Asia, (so not a lot of tech support in English)
• Local drinking water is questionable, so we always make our own.
• Harbor water can be polluted, so prefer to fill tanks underway before arrival
• Carry 1300liters of water (340 US gal)
• 3 people, navy shower twice a day and we have 1 fw toilet, so are probably considered heavy users.
• Presently have a 1990 HRO System 9/500 that makes about 21USgal/hr. running a 1.6hp 220/240v AC, single phase that consumes 2.0 Kw from my 10Kw generator.

Reasons to consider upgrade

• We are a motor sailor, so when the wind is contrary or less than 12-14knts, I motor sail, charge batteries and would like to make water, without running the Gen. as the Main Engine, is just loping along without much load at low rpm.
• I recently installed a large AGM house bank 1040 Amp hrs @ 24v and use only 9% capacity in 24 hrs, so there is a lot of reserve capacity to run a DC R/O motor at extended anchorage and with 2 x 24v Victron charging units 50a and 70a, I get fast recovery when using the Gen at anchor.

1/ So I am weighing the idea (and cost) to switch the existing R/O to a DC motor or whether the more modern energy efficient pumps justify a complete new system?

2/ If new, should it be a smaller capacity to balance DC demands with charging rates, or go with a high capacity for quick make up as Nick from s/v Jedi likes?

3/ Which suppliers would be on your shortlist?

It is getting time to change the membrane anyway (10 years), so would appreciate thoughts on the big picture first before focusing on any specific supplier.

Thanks for your help

[Therapy]

If many ports/harbors have "bad" water in them I would suggest a higher capacity one.

That is all I can offer.

[Pelagic]

Hi Therapy, between port cruising is usually 6 to 7 hours and we don't stay in dirty ports for so long, it is just that I don't like running the 10kw Gen underway for just a small 2kw AC load, hence the interest in a DC solution for underway charging off my alternator

[Stillraining]

I have nothing to offer Pelagic...

But your DC plan sounds like a win win to me...I would/will design mine to run off the main engine if I ever install one...killing two birds with one stone as well...charging and making water....but your method works equally well if not better...I always planed to go with around a 30 to 50 gal per hour unit to keep run time down ....so I would fall into the start over camp I guess, as long as your changing so many other things as well.

What kind of amperage will that DC motor draw on your current pump compared to an upgrade?

[Pelagic]

Originally Posted by Stillraining

I have nothing to offer Pelagic...

What kind of amperage will that DC motor draw on your current pump compared to an upgrade?

I think that is the $50 question which is why the energy efficient ones are also being considered

[hummingway]

Its on my list of decisions to make (and move on) and I came across this and I would love to hear others thoughts:
Choosing the right watermaker for you

[Pelagic]

Hummingway, that article is a good primer and seems to support Nick on Jedi’s philosophy to go large and make water quickly using your available Gen, while doing other things.

If I were to breakdown the 3 choices for my application I see these pros and cons:

Present Set Up
AC pump and Gen making 21 US gals/h while charging batteries, making bread, running air con for 3 hours a day, so the Gen is well loaded up.

Pros: Efficient use of existing Generator power to make water
Cons: All eggs are in one basket, if Gen fails…. No water!

Main Engine PTO for pump:
I already have a crash Emergency Pump, large case 24v Alternator for house bank and a small 24v automotive type alternator for start batteries, so I am maxed out up front. Also, Main Engine (6 Cylinder Perkins Turbo) is too big to run at anchor for just making water. Not attractive to me

DC Conversion: ...Low Energy Systems like HRO Seafari Escape, Spectra, Schenker or others at about 16.5 gals per hour drawing 12 to 13 amps @ 24v

Pros: Multi sources available to charge batteries to supply pump so making water should never be an issue at anchor or motor sailing.

Cons: Questions about whether this provides enough cross flow for membrane longevity
Scheneker owners have complained about higher salinity.
I know costs are higher but what other trade offs is there with these types other than proprietary equipment that may be hard to replace in remote areas?

The Schenker Smart series SCHENKER ITALIA DISSALATORI WATERMAKER
claims the best DC power efficiency of these new breed, but I know nothing about them or their customer loyalty, which Spectra seems to have achieved.

Hopefully someone with a Schenker unit will chime in

[capt_douglas]

I like Sea Recovery, Spectra, and PUR. We've got 2 Sea Recovery units onboard (1000gpd each) and after nearly 10 years of use, aside from changing the membranes and replacing the HP hoses (mostly as PM, not as a failure), it continues to work. Many of the large yachts use these, and while they can be pricey and large, they work - and that's more important to charter guests, owners, and most importantly, crew, than the power required to make water.

If you want to make water while your motorsail then it sounds like you're going to have to put efficiency (gph/amp) ahead of probably gps. I know a number of boats that have gone to big inverters and alternators to provide the DC power to run the system while provide enough reserve to charge batteries.

I'd suggest a good prefilter system as that can really prolong the low pressure pump and membranes. Sand filters are huge but most of us get by with big synthetic filters (20 & 5 micron) on the front end.

[JayH]

My Spectra system makes water at about 18-20 gal/hr using two DC feed pumps and one membrane. I'm surprised to hear that your output isn't much better for much higher power needs.

Making water is not a quiet process for me. My pumps drone and my discharge gurgles. We are heavy users too and probably make water 3-4 hours a day on average. So getting it over with fast and then doing something else has real attraction.

However, I wouldn't change from DC for one reason. Water is a critical system. It just has to work. I can be out of fuel, all three of my engines can be down, my inverters can be dead, maybe even my batteries can be shot, but as long as the sun is shining I can still make water from solar. Solar panels are pretty reliable, and as long as I don't ruin the membrane somehow, I feel pretty confident that I can keep the Spectra working. It has redundant pumps and I carry spares. The Clark pump is an unknown, but I've never had a problem. I just sent it in to get rebuilt for good measure, and I think most problems can be addressed in the field with a rebuild kit.

Lastly, I cannot make water underway. I think my intake isn't far enough below the waterline. If you're already making water underway then it must not be a problem for you, but if not you may want to consider that it might not work.

[nhschneider]

I'm guessing that JayH and I have the same Spectra watermaker. The model I have is called the Cape Horn and it's Spectra's model that has no electronics. The unit makes about 15 gallons/hour and uses about 18 amps per hour at 12VDC. For the last 2 years, we have cruised the Sea of Cortez during the winter and our watermaker has been one of the most reliable and easy-to-use systems we have on the boat. We tend to run it about every other day for a few hours, giving us more than enough water for showers, cooking and even an occasional wash down of the decks. I do not police water usage but I don't consider myself wasteful, either. My wife, on the other hand, nah, never mind, better not go there . . .

[Pelagic]

Thanks Jay and Nschneider ....Is the Spectra Cape Horn and the Cape Horn Extreme the same unit?

That no frills unit is attractive to me, but I wish it had a bit more production so in the Spectra range the Newport 700 Mk II is more what I was hoping for, but I have yet to cost it

[JayH]

My install is older than Specta's current marketing, but it looks similar to the Cape Horn Extreme (simple and modular). I notice they are only claiming 330gpd for the Cape Horn. The literature I have from mine claims 380, but I think they probably backed off from that to lower expectations.

I am 99% sure that you can easily increase production of these machines by adding another membrane in series. The membrane rejects 90% of the feed water as brine and the other 10% is product. My understanding is that by running the brine into another vessel and membrane, you can turn 10% of that into product water and almost double your capacity. I think this is all they're doing for the 700/1000 machines.

Spectra's are not cheap by any means. If you are so inclined I will simply observe that for my system the Clark Pump is the only part they actually made. Everything else can be had off the shelf. Now if you're interested in their Z-Brane stuff or MPC controllers that is a different matter, but the fancy ones don't meet my requirements for being both simple and bulletproof.

[Pelagic]

Thanks Jay,,,,I wonder if Tellie is around to be able to confirm that I can get a no frills 700.

I will try and PM him.



Still would be interested to know more about the Schencker

[Nauticatarcher]

I'd tend to work on the basis of if its not broken dont fix it, if you have had 10+ yrs out of your current system and it has met your needs , why change?, maybe look at large inverter to run watermaker whilst motoring, we used to be able to run ours of inverter, but due to poor ventilation inverter would trip out after about 1/2 hour as it would overheat working that hard, but that was an inverter installation problem not watermaker

[Paul Lefebvre]

I was going to suggest the same as Nauticatarcher. If you don't have a large inverter, you may want to price it out in comparison to the other options. With your large battery bank, it may also give you other options for 240 Volt power on board in place of running the genset at times. Of course, the power consumption for making water will not be an issue while motoring underway..

The startup amps on the AC motor may be a problem though, depending on the surge capacity of the inverter.

New menbranes are less than $200, so not the greatest justification to change out a whole system. However, you may want to add a second membrane in series with the first one to double your capacity. That would be around $550 for a new vessel and menbrane (2.5" x 40")


Paul