Do Watermakers Work in Fresh Water?

[Tellie]

Ghaffy, I know that boat yard, right off the train station Donaumarina U right? My daughter goes to the university and has an apartment near the Messe Prater U station. I get off at that station when I ride my bike into Bratislava (love biking all over that area) Are you there year round? I'll have to stop by next time I'm over there on one of my Bier Beisel Bike trips, knock on your hull and buy you a few Ottakringers.

[ghaffy]

Tellie,

you won't find me there but half an hour upriver at Korneuburg.

So send me a message once you're around, and I'll be there (or anywhere else) 30 minutes later.

[boatpoker]

Don't know squat about this topic but I did have a dock neighbour (yr. round liveaboard) for ten years in Lake Ontario who drew lake water through a charcoal and UV filter system he built from Home Depot parts. He occasionally had the water tested and it always tested cleaner than municipal water.

[Tellie]

Originally Posted by ghaffy

Tellie,

you won't find me there but half an hour upriver at Korneuburg.

So send me a message once you're around, and I'll be there (or anywhere else) 30 minutes later.

Well I was there a few months ago but now back in sunny rainy S. Florida. But I'll be back next year with another bike trip planned and I'll surely send you a message and stop by.

[Amapola]

We've used our watermaker in fresh water as long as the water is clean and clear. Our manufacture rep said that if it is clean enough to swim in, it's ok to use it in the watermaker.

[Jane.Joy]

Originally Posted by Amapola

We've used our watermaker in fresh water as long as the water is clean and clear. Our manufacture rep said that if it is clean enough to swim in, it's ok to use it in the watermaker.

We use our watermaker in water that I wouldn't for a million dollars swim in. My understanding - it's only chlorine and oil that ruins the membrane - everything else is fine, as long as you have enough pre-filters and you can bear the stink of changing them, when you make good clean water out of nasty germy water.

[ryon]

Yes, they do. You just have to wire them backwards, so they work in reverse-reverse osmosis.

Why are you making salt water, may I ask?

[Tellie]

My advice is always the same. SW watermakers are offshore pieces of equipment. Especially if you would like them to last for their intended purpose. Will they work in fresh water? Absolutely, as long as you either manually adjust the pressures and flow or your system does it automatically they will make more water in fresh than they will in salt water. Most people don't understand the pressure and flow relationship of membranes. SW membranes being run in fresh water are often operated at higher flow rates and less pressure. This can and does over time damage the SW membrane. There's a reason they make Salt water, Brackish water, and Fresh water membranes. But if controlled right they will make great water in fresh water. The problem is pre-filtration most salt water systems pre-filtration is not adequate for the type of contaminants more often found in fresh water. Especially salt water boats that travel from salt water enviroments into fresh water enviroments. Many times these areas of transition are feed from rivers and streams which have loads of growth, sediments, etc., quickly clogging the pre-filters. In theory you could put the input of your SW watermaker into a septic tank and make drinkable water, until you clogged the system. One of those "Don't try it at home things"

[syd spray]

from ishipaco's site : Katadyn and PUR Watermakers: Installation, Maintenance and Troubleshooting

Can I use my watermaker in freshwater? The short answer is—yes. There's nothing about this subject in the Katadyn Owner's Manual, but I've had verbal confirmation from the Katadyn engineers in Switzerland: processing freshwater will not damage a Katadyn watermaker.
At the present time, I am not aware of any competing brand of watermaker whose manufacturer recommends using their watermakers in freshwater; and the common wisdom among owners of those brands is that freshwater input is not allowed. I suspect that this may be because most other brands of watermakers have pressure regulators which the user can adjust. Watermaker membranes can be damaged by internal pressures that are too high and, because of the complex physics of reverse osmosis, the chances of overpressurizing the membrane are greater when processing freshwater. It is possible for a user of other brands of watermaker to accidentally damage the membrane by adjusting the working pressures, even when using a setting that would be perfectly O.K. when processing seawater. Because of this, the rumor among cruisers is that watermakers should not be used to process freshwater. It may be that Katadyn watermakers, with their system of automatic internal pressure regulation, are the only exception to this general belief. As far as I know that is, indeed, the case.
I became interested in this subject after reaching the Caribbean side of the Americas and while spending a hurricane season at Mario's Marina in Rio Dulce, Guatemala. The marina is about twenty miles up the river, far from the ocean. I've never taken on dockwater while cruising foreign waters and didn't want to start there. So I ran my watermakers (a PUR Model 35 and a Katadyn Model 40E) while tied up to the dock for almost six months. A couple of years prior to that, I had run my watermakers in the estuary at Bahía de Carácas, Ecuador, for six months. The water there is a dirty mix of fresh river water and seawater.
Although Katadyn watermakers will work well with freshwater input, I have a word of warning. Most freshwater situations should be considered "enclosed water spaces." In such locations, especially in third world countries, rivers are often used—legally or otherwise—as sewage systems. The more populated areas there are upstream from your location, the more likely you will be exposed to various kinds of contaminants—everything from human waste to petroleum products to pesticide runoff. Your chances of experiencing problems from such sources are significantly greater than when in the open ocean. Keep this in mind.
In my own case, to be honest, I had to replace my membranes after six months making water in the Rio Dulce. The membrane elements became slimy and over time the TDS readings rose gradually to the 6-700 ppm range. Bottom line: the problem isn't freshwater, per se, but what other things are likely to be found in the freshwater.