Watermaker Membrane - Change to Larger = Increased Output?

[BlueSovereign]

I have a 6.5kWGenset, and am installing 900A/hr capacity with 2000 watt inverter though I doubt that is my issues.

I most certaining could not have a pump near the engine ... no room for even a second alternator.

I was told with AC you can have a more powerful motor and thus enable making more water in a given time (system capability permitting).

[Cheechako]

I believe most 120v will make a lot more water faster, just due to the avail HP. If you already have a gen set and plan to keep it.... 120 might be great. I would stay away from a bunch of fancy bells and whistles though... "let your taste buds do the walking"

[BlueSovereign]

I'm in NZ so it will be a 230AC system. Thanks for the input.

[s/v Jedi]

The difference between boats with AC powered watermakers and boats with DC powered watermakers is that the DC boats wash their decks with salt water and the AC boats use fresh water.

BTW: the membranes are cross-flow filters. This cross-flow is what cleans it and without that you quickly loose the membrane. When we make 50 gph, we have 120 gph brine discharge. Without any pressure, the pump delivers 180 gph which goes out the brine discharge.

cheers,
Nick.

[Tellie]

"The difference between boats with AC powered watermakers and boats with DC powered watermakers is that the DC boats wash their decks with salt water and the AC boats use fresh water"

I don't know about that. I wash down my boat, gear and flush the dingy's motor with water from a DC unit. 50gph on a 48 foot sail boat is A LOT of water. Watermakers like to be run often to stay healthy, and that is the key to sizing one for your needs. There are certainly those people who like three showers a day, clothes washers on board, freshwater flush heads, the ability to let the faucets run without concern etc. For those lucky folks a 50gph watermaker would be handy. For the rest it's a bit over kill. Most sailors just don't use that much water. If you have a generator on board and are going to rely on it to make water if it fails (I've never ever ever heard of anybody with generator problems) so does your watermaking capabilities. A 2000 watt inverter probably won't run a 50gph watermaker. Even if you installed a inverter large enough to run a 50gph watermaker and your generator fails, with 900 amps you wouldn't be happy with the amp/watt cost of a gallon of water made. There are a lot of variables that need to be considered when deciding on a watermaker be it DC or AC. Again the Tim Allen school of bigger is better doesn't really apply to watermakers. But if you still insist on a large producing AC watermaker for your boat I'd a wait just a little bit longer, there is some new stuff coming out that will be worth the wait that just might make the big pumpers obsolete.

[witzgall]

Care to elaborate?

Chris

Originally Posted by Tellie

[B
But if you still insist on a large producing AC watermaker for your boat I'd a wait just a little bit longer, there is some new stuff coming out that will be worth the wait that just might make the big pumpers obsolete.

[svquest2]

A larger motor is not going to give you more water. If your pressure and volume is predetermined for a given volume of product the only way to get more water is to add membrane. Too much pressure will destroy the membrane and drive stuff through that's not supposed to go through.

With my 600 GPD unit I cleared 20+ GPH and not quite the 24 I was supposed to get. None-the -less I ran the WM for 2 to 6 hrs /week to make up for the water we used (depending on showers) and I guess we could have run it more to wash decks but thought that the 2-6 h/wk were enough. We used it for our water needs (Except deck washing) for 6 years in Mexico. We never trusted Mexican water. It's now pickled, now that the boat is home.

Joe S

[Tellie]

SVquest is correct. It is all based on pressure, flow and volume. Just adding more membranes to a watermaker without taking into account the delivery capabilities is not going to work any better than adding a larger pump and motor to a smaller membrane. There are balances between the two that have to be met to work properly and efficiently.

[quartersplash]

Thanks for all of the replies. To answer a question from a couple of you. I have a village marine 150 gallon per day 12 volt unit. To the gentleman from Washington with the aqua marine H2O maker. I am from Tacoma and I had one from him on my other boat that was engine driven and worked fine with no problems. I may try and give him a call.

[s/v Jedi]

Originally Posted by Tellie

I don't know about that....
[...]
But if you still insist on a large producing AC watermaker for your boat I'd a wait just a little bit longer, there is some new stuff coming out that will be worth the wait that just might make the big pumpers obsolete.

Of course I was making fun with that AC vs DC statement but you must admit there's some truth in it.

However, you clearly don't understand why an AC watermaker must be a big one. The real reasons are that a diesel genset (and you better have that, no Honda 2000i's for this) wants a good load when it runs and a big watermaker helps. Also, we want to run the genset as little as possible so we want to produce more water in less time. It's the other way around with a DC WM.

Also, I don't understand your issue about not being able to run the WM when the genset breaks down. Surely, the AC WM owner thought about that and has the inverter to run it and the alternator(s) on the main engine(s) to provide the power for the inverter. Battery bank capacity is not an issue. Also, it doesn't matter what capacity the WM is for energy consumption. It is the energy-efficiency that matters (not that small AC units are very efficient).

On to the systems that use water. Yes, I admit we have fresh water flush toilets and a washer drier. The fresh water flush toilets save us money, nasty smells and time consuming maintenance jobs. The washer drier aboard is more energy efficient than the coin operated one ashore and much closer by... especially when you're at sea or anchored far from laundromats. I take your remark about letting faucets run without concern as a joke because I know no cruiser who does such a thing.

Let me describe our routine for running our 6 kW genset: It warms up for 5 minutes or so before we switch the 16 kBTU A/C unit on. Next is the 50 gph watermaker and next the battery charger. This brings the genset to 80-90% load so it really heats up and that heat is used for the water heater which is plumbed into the coolant circuit. Soon (15 minutes), the load comes down a lot because the batteries are full (solar power) so we get the vacuum cleaner out (3 cats aboard...) which takes 1500W again. Vacuum cleaning is nice with that A/C unit blowing around our heads. Meals are cooked which is also nice with the A/C on and by now it produced a couple of gallons of condens water already which would otherwise be somewhere in the boat stimulating mold and mildew gardens. An hour after we started the genset, all gets switched off, meals are served in the cockpit and a nice cool cabin is waiting, plus 50 gallons of water for the 3 hot showers tomorrow (must be another joke ;-)

So, what does this cost us? 0.5 gallons of diesel, let's say $1.20 plus an hour run time on the genset. Good deal isn't it? We do this like once a week normally. Sometimes less when it rains good (we catch rain water too) and sometimes more when it rains long (more A/C and more power needed for entertainment). We do it daily when on passage for too many reasons to list.

Before all this we had DC watermakers. We had a lot of trouble with them, that's all I (want to) remember. But imagine this: you can't have the A/C luxury, can't play loud rock music on passage (not enough power because the AP and navlights need it all), have to cook lousy meals (cans are on the menu mostly) etc. We did all that and we were happy. But we're happier now!

Now, tell us about that new stuff that's coming out!

cheers,
Nick.

[Tellie]

Nick, yes they were jokes poking fun and I wasn't intending them at your expense. I apologize if you took it that way.
Actually I understand watermakers fairly well, AC included. We have installed plenty of AC watermakers on boats and land based, some making far more than 50 gallons an hour. But, for most sail boaters an efficient DC system is a far better way to go. I take that just from experience and boat owner interaction. I hear all kinds of stories from all kinds of folks about all kinds of watermakers. I've said it before on this board many times that most watermaker companies make a good unit that if properly taken care of will service them well. I also maintain and will stick by, again through experience, that there is no one size fits all watermaker. A watermaker without question for most boaters is a serious investment. There are a lot of variables to consider and questions to be asked before making that decision. I try to help people walk through that process. Do I have a preference to a particular brand? Yes, but that's no secret for those that know me here. Would I like folks to buy from me? Of course. But if someone wants another brand I will take all the time they want and need to explain it as well. In fact I'll talk someone out of a watermaker if that makes more sense for them. Ultimately it's like anything you own. If it makes you happy two years later then it's probably the right one for you. Just a quick note as to your run time, again from experience, an hour run time once a week on your membranes is a bit short of what most watermaker manufacturers will tell you. They should all tell you, watermakers like to be run at least a few hours each week. A 50gpd watermaker usually has three 40" membranes that need enough flow time across them to keep them healthy. That is one of the reasons as I stated before that bigger is not always better. As far as the new stuff, patience.

[jackmox]

Hi from ken regarding your water maker project just to add more membranes will not work, the thing is although the more membranes, the more water ( pure) you get, more membranes needs more pressure to get the water through them, they are not like filters, they have a large quantity sea water going through them but only say 10 to 12 % of pure water is produced at the other end, you will also see that a 12 volt system uses a lot of power its mormal for a 12 volt system to use 30 to 40 amps so most boats will need to have a relay that only turns the water maker on when the main engine is running, ie charging the batteries,

hope that helps
regards ken

[s/v Jedi]

Wow, another old thread that gets a wake up call... but this one needs it:

Originally Posted by Tellie

But if you still insist on a large producing AC watermaker for your boat I'd a wait just a little bit longer, there is some new stuff coming out that will be worth the wait that just might make the big pumpers obsolete.

Originally Posted by witzgall

Care to elaborate?

Originally Posted by s/v Jedi

Now, tell us about that new stuff that's coming out!

Originally Posted by Tellie

As far as the new stuff, patience.

So, 2 years down the line... come on, tell us about the new stuff now! :-)

Originally Posted by jackmox

Hi from ken regarding your water maker project just to add more membranes will not work, the thing is although the more membranes, the more water ( pure) you get, more membranes needs more pressure to get the water through them, [...]

Hi Jack... yes I never made it clear that I only have 2 membranes and only get the 50 gph output because we're in the Caribbean with very warm water. In cold water it'll go down to 40 gph.

cheers,
Nick.

[Tellie]

Originally Posted by s/v Jedi

Wow, another old thread that gets a wake up call... but this one needs it:









So, 2 years down the line... come on, tell us about the new stuff now! :-)



Hi Jack... yes I never made it clear that I only have 2 membranes and only get the 50 gph output because we're in the Caribbean with very warm water. In cold water it'll go down to 40 gph.

cheers,
Nick.

Yeah old thread for sure.

How about 75 gph for 7.5 amps on 110V or 3.8 amps on 220V

[s/v Jedi]

Originally Posted by Tellie

Yeah old thread for sure.

How about 75 gph for 7.5 amps on 110V or 3.8 amps on 220V

That's 50% more efficient than what I have (I still have the same 2-membrane, 1.5hp AC unit, same membranes). I guess it is a high volume Clarke pump or something? You have any pointers?

cheers,
Nick.