AC/DC/EngineDriven Watermaker Pump?

[Arthurc]

I’m starting to look at watermakers for my KK54 and have read many of the posts in here but the thing I am struggling with is what to drive the watermaker with. My understanding is that you don’t want to run it at anchor or moored as lower quality water = less life and more problems out of the system. So if that’s the case what are the advantages or disadvantages of a DC, AC or Engine Driven system? While more to go wrong I think I have a 200a alternator + a 75a alternator so might be simplier to just put on an AC or DC one versus messing with engine driven?
To make matters a bit more complicated I am planning on replacing the Lehman 225 engine with a JD this winter so hence any engine driven system wouldn’t get installed until the engine swap is done.

Thoughts?
AC

 

[MYTraveler]

You also don't want to run while underway if that will introduce air into the system. Engine driven pumps can be complicated, especially with a variable rpm engine. A genset take off is probably preferable to the mains, but electric is easier. I make water while at anchor, but only on an incoming tide.

 

[Arthurc]

You also don't want to run while underway if that will introduce air into the system. Engine driven pumps can be complicated, especially with a variable rpm engine. A genset take off is probably preferable to the mains, but electric is easier. I make water while at anchor, but only on an incoming tide.

Interesting, thanks. On the electric system are you DC or AC? The one advantage I would see with DC is it can be fed right off the alternator on the main engine but if you only run at anchor then AC would be just as good...
All the research I have done points to using as generic parts as possible so may go with the guy who seems super highly rated and sells on eBay.
AC

 

[Larry M]

I wouldn't do an engine driven system since rpms influence the pumps pressure. If you have solar, a DC system would be a consideration. We run the generator a few hours per day usually with excess capacity. AC water makers have worked for us over the last 20 years. At ~25 gph, we've never been short of water. You can increase the capacity from 25 to 50 gallons per hour pretty inexpensively if you want that volume.

You can also run an AC water maker off your inverter based on your sizing.

 

[Bruce B]

Having used a 12 volt Spectra watermaker for the past 15 or so years we always felt that it was a great addition to our cruising lifestyle. On our new boat we switched to a 40 gph (at warm water temperatures) 120 volt system and we could not be happier. We have used ours from Canada to Long Island and to Bermuda without issues at anchor or at sea.
Just use it regularly and you will be fine. I never use it in obviously polluted waters though.
Bruce

 

[BerettaRacer]

No problem running watermaker at anchor or clean dock as long as not stirred up or silted flow. Wouldn't do it in crowded marina.
My last boat it was standard procedure to make water while docked in front of the owners house in the Bahamas, we had more and better water than the locals.

 

[MYTraveler]

Interesting, thanks. On the electric system are you DC or AC? The one advantage I would see with DC is it can be fed right off the alternator on the main engine but if you only run at anchor then AC would be just as good...
All the research I have done points to using as generic parts as possible so may go with the guy who seems super highly rated and sells on eBay.
AC

220 vac. I am in the process of replacing both of my water makers with home made from parts I could scavenge from the old systems. One is done and making 45 gph with about 150 ppm of TDS. The next one will be microprocessor controlled (so monitoring/controlling pressures, quality, flow rates many times per second, with automated freshwater flush), then I will retrofit the first to microprocessor control. My primary motivation was the exorbitant price charged for proprietary parts. Like $150 instead of $950 for a new RO membrane.

 

[Lepke]

I've had both electric 240 and engine driven on a 4108 Perkins generator. The problem I run into is light loading of the Perkins. Just like light electric loads. It runs at 1800 rpm but only needs 5-10 hp. I can't seem to find enough ac needs when I'm making water. Now that the engine has a new build, I don't want to glaze the sleeves again.

 

[Larry M]

.... My primary motivation was the exorbitant price charged for proprietary parts. Like $150 instead of $950 for a new RO membrane.

We have a Village Marine unit with a 38" proprietary membrane. We were getting ready to change out the pressure vessel and membrane when Parker, after they bought Viilage Marine, changed the pricing to be more in line with the Dow Filmtec 40" standard membranes. The Parker membranes are still more expensive at around $300 but now it's not cost effective to me to modify the system.