Watermakers and Harbors

[billknny]

Originally Posted by Rainman

Membrane production reliability may have improved since you were doing your work with 20% membrane fault rate. In the last 800 Filmtec SW30 membranes we have installed in our systems, we have only had 11 (1.4%) that didn't pass our internal TDS tests. We pull those out and swap them before shipping. My apologies if I misunderstood your comment about 20% membrane test failure.

Production membranes will always (or so close to always it matters not) pass a TDS test. My point is that a TDS test is not good enough. You can have a membrane that will give a good pass on TDS and still leak enough raw a water to be biologically unsafe.

The test I am referring to is called a "bubble point" test that is designed to find ANY leak in the final installation of 0.22 microns or larger. The test is performed on the membrane installed in its housing. The 20% failure rate includes failures of the seals isolating the feed and permeate sides of the membrane. Most of the failures came from the seals, not the membranes.

And you are right, I dropped a "9"... membrane rejection rate is 99.4% not 95%!

[scarlet]

Out of curiosity... how much do those membranes cost?

[IanTrail]

We spent 2 years cruising the eastern Caribbean from Venezuela/Trinidad up to the VIs and Bahamas and it was mostly anchoring in good to excellent water. The watermaker was essential because taking on water was inconvenient, expensive or impossible. OK, don't use in grotty harbours but they are few and far between. The things that kill watermaker membranes are oil and chlorine (flushing from shore supplies).

We have been living from a watermaker for 9 years now without contamination problems. However, while we hope that the watermaker is putting clean water INTO the tanks, what comes OUT may be a different matter. Because the tanks are unchlorinated (for flushing), they might be a bit buggy. So we use tank water for everything except un-boiled drinking, for which we use bottled water. Tea, coffee and cooking seem OK.

My overall verdict is that you can't live without one, specially in the Caribbean.

[IanTrail]

My watermaker has 2 membranes at about GBP150 each. They last 5-7 years if flushed regularly.

[GordMay]

Greetings and welcome aboard the CF, IanTrail.

[Tellie]

I gotta run another watermaker class. Good luck finding anyone that has ever run a bubble test on a boat based watermaker, ( But I suppose there is always the exception to the rule). All membranes are NOT created equal. Even among the same batch made they will come all come out different. How much this difference makes in a boat based watermaker is usually insignificant. Your real threat from the little nasties that live in water will for the most part always come from your fresh water tank not your good working watermaker or the surrounding water that is feeding it. Also, people who fill their fresh water tanks with only RO water are actually running more of a risk of tank contamination than those that occasionally fill their fresh water tanks with reliable dock water. There is a reason municipal water has chlorine in it and the same principals apply to your fresh water tanks. Anyone who states that a good quality filter is not needed after your fresh water tanks is not understanding of boat fresh water tanks in the real world. Long ago I invested in a plumbers scope to see into peoples fresh water tanks. Most people are surprised and usually that day order a filter for at least the taps they will consume their water from. Sterile water? No one has probably ever tasted it. Most of your life you have been drinking water that has some life form in it. The human body is pretty good at taking care of that. I assure you you have had food out at your favorite restaurant that has contained more biological bombs in it. So in short, a well made watermaker (and there are many) taken care of, a good (not cheap) point of use filter, and cleaning your tanks every now and then and 99.999% of you will be just fine drinking water that is better than the best city municipal water you can find.

[MV Wanderlust]

Originally Posted by Tellie

I gotta run another watermaker class. Good luck finding anyone that has ever run a bubble test on a boat based watermaker, ( But I suppose there is always the exception to the rule). All membranes are NOT created equal. Even among the same batch made they will come all come out different. How much this difference makes in a boat based watermaker is usually insignificant. Your real threat from the little nasties that live in water will for the most part always come from your fresh water tank not your good working watermaker or the surrounding water that is feeding it. Also, people who fill their fresh water tanks with only RO water are actually running more of a risk of tank contamination than those that occasionally fill their fresh water tanks with reliable dock water. There is a reason municipal water has chlorine in it and the same principals apply to your fresh water tanks. Anyone who states that a good quality filter is not needed after your fresh water tanks is not understanding of boat fresh water tanks in the real world. Long ago I invested in a plumbers scope to see into peoples fresh water tanks. Most people are surprised and usually that day order a filter for at least the taps they will consume their water from. Sterile water? No one has probably ever tasted it. Most of your life you have been drinking water that has some life form in it. The human body is pretty good at taking care of that. I assure you you have had food out at your favorite restaurant that has contained more biological bombs in it. So in short, a well made watermaker (and there are many) taken care of, a good (not cheap) point of use filter, and cleaning your tanks every now and then and 99.999% of you will be just fine drinking water that is better than the best city municipal water you can find.

Good guidance. Thanks, Tellie.

[BobHorn]

I think the main issue with making water in harbors is clogging the pre filters and adjusting the back pressure to match the salinity of the feed water. Less salinity, less back pressure. To make the admiral happy I installed a UV sterilizer on the output, less than $200, I think.

[a64pilot]

It’s just dead easy, and cheap to install a standard 10” filter just after your water pump, go to Lowe’s or Home Depot etc and get one, then decide if you want a carbon block filter or just a sediment filter.
Maybe the same cartridge your watermaker uses anyway so you already carry filters.

[SV THIRD DAY]

Originally Posted by Tellie

I gotta run another watermaker class. Good luck finding anyone that has ever run a bubble test on a boat based watermaker, ( But I suppose there is always the exception to the rule). All membranes are NOT created equal. Even among the same batch made they will come all come out different. How much this difference makes in a boat based watermaker is usually insignificant. Your real threat from the little nasties that live in water will for the most part always come from your fresh water tank not your good working watermaker or the surrounding water that is feeding it. Also, people who fill their fresh water tanks with only RO water are actually running more of a risk of tank contamination than those that occasionally fill their fresh water tanks with reliable dock water. There is a reason municipal water has chlorine in it and the same principals apply to your fresh water tanks. Anyone who states that a good quality filter is not needed after your fresh water tanks is not understanding of boat fresh water tanks in the real world. Long ago I invested in a plumbers scope to see into peoples fresh water tanks. Most people are surprised and usually that day order a filter for at least the taps they will consume their water from. Sterile water? No one has probably ever tasted it. Most of your life you have been drinking water that has some life form in it. The human body is pretty good at taking care of that. I assure you you have had food out at your favorite restaurant that has contained more biological bombs in it. So in short, a well made watermaker (and there are many) taken care of, a good (not cheap) point of use filter, and cleaning your tanks every now and then and 99.999% of you will be just fine drinking water that is better than the best city municipal water you can find.

Bingo....
But I did laugh out loud and woke my wife up in bed next to me when I read about the Bubble Test...ha ha ha...

[SV THIRD DAY]

Originally Posted by a64pilot

It’s just dead easy, and cheap to install a standard 10” filter just after your water pump, go to Lowe’s or Home Depot etc and get one, then decide if you want a carbon block filter or just a sediment filter.
Maybe the same cartridge your watermaker uses anyway so you already carry filters.

that exactly what we do...save the Bubble Test for the Chat Room Experts

[SV THIRD DAY]

Originally Posted by scarlet

Out of curiosity... how much do those membranes cost?

The Gold Standard of RO Membranes are the Dow SW30-2540 or SW30-2521. Prices range from $187 to $200. At a realistic life span of 5-7yrs...that's pretty low cost.

[a64pilot]

I should say that a filter unless it releases chlorine or has a UV light or something similar isn’t going to do anything at all to prevent a virus or bacteria from going right through. It’s there for taste and sediment.
My tank is old and apparently has spent a lot of its life with hard water being out into it, so therefore it is lime covered and releases bits of this lime from time to time, without a sediment filter bits of this lime will clog the water sprayer on the sink etc. a sediment filter prevents this, and since you can get a carbon block filter for so little money, why not?
But it’s not going to trap things that will make you sick, or not likely to anyway.

[Pelagic]

Hi Rich and Tellie....
Which method is better?

1..... To treat storage tank water with filter or UV sterilization?

2....Should you put filter on suction side of water pump, or pressure side?


Absolutely right, your storage tank is the biggest danger if not cleaned regularly.....
Luckily I am able to stand in mine and inspect once a year

For me, the litmus test on whether I make water in harbours is the amount of flushing action from tidal movement and how enclosed it is.

I also avoid making water in heavy rains when accelerated run offs from roads and rivers creates a soup of suspended matter.

[nwdiver]

Originally Posted by Nightsky

A UV filter of your product water prior to entering FW tank will take care of anything that gets past the RO membrane.

Or a UV filter on the fresh water line to the galley sink used for drinking water kills anything growing in your tanks.......I can't hit them with bleach as I use the water to back flush my watermaker......