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Old 07-07-2012, 20:21   #16
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Tie the dirty pleated filter element to a line and tow it behind the boat a bit while using a 2nd filter. Switch the two when needed.

cheers,
Nick.
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Old 07-07-2012, 21:26   #17
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Re: Watermaker pre-filtration and sea water "quality"

If you think coastal Masschusetts waters are tough on watermaker filters - wait until you get to Maine
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Old 08-07-2012, 04:18   #18
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Re: Watermaker pre-filtration and sea water "quality"

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Originally Posted by s/v Jedi View Post
Tie the dirty pleated filter element to a line and tow it behind the boat a bit while using a 2nd filter. Switch the two when needed.

cheers,
Nick.
We have cleaned the two filters that were previously used and I'll try them again in the next day or so. The system has been in its self-flush mode for a few weeks while we have transited the Hudson, Erie, Rideau, and St Lawrence. We will be transitioning into the St Lawrence Gulf over the next day or two and I plan to fire it back up when the water looks consistently good.
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Old 08-07-2012, 05:15   #19
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Re: Watermaker pre-filtration and sea water "quality"

Oh boy, I know I'm starting to sound like an old nagging hen here but I'm really just trying to help you guys.
So a little more clucking about pre-filters.
First, on the idea of dragging filters behind a boat. A Grand Banks is capable of a lot more speed than a sail boat. At cruising speed you'll probably destroy the pre-filter, especially the cheaper ones with cheap inner cores. Not all filters are they same just because they are of the same micron rating. Secondly, a pre-filter can work both ways. They are intended for the water flow direction to be from the outside of the pleated material towards the inside. When you drag a filter behind a boat yes you flush the outside but you also force water through the end of the filter facing the stern through the filters core. That water, at many times the volume and pressure found inside the watermaker, is being filtered in the opposite flow direction because the stopper knot you've tied to the end of the rope blocks the water from exiting, so it has no where to go but through the reverse side of the Pleated filter surface. You are effectively filtering hundreds and hundreds of gallons of water in reverse and coating the inside surface with the same things you are trying to filter out when you run the watermaker. Now you take this filter, put it back into the watermaker and start it up. Now you are estentially back flushing this filter and all the crap you've filtered by dragging it behind the boat directly into the watermakers pump and membrane. This is one of the reasons watermakers do not "back" flush, they instead fresh water flush in a forward direction.
All you really need to do is to gently rinse off the surface with a little fresh water. Never scrub the filter, bleach it, or rinse it under high pressure from a hose nozzle. It will never be white again, but if changed soon enough, you should get 5-8 uses out of it before you throw it away.
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Old 08-07-2012, 05:25   #20
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Re: Watermaker pre-filtration and sea water "quality"

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Originally Posted by twistedtree View Post
The boat came from the factory (Grand Banks) prepped for a watermaker, and I did the install on the Catalina. And yes, it's a MkII 300 MPC 5000.

I'm happy to answer any questions about the install. I think I did it all correctly according to the docs from Spectra, but welcome any thoughts on improvement. Here's the basic setup:

- Groco BVS750 3/4" combination thruhull, valve, strainer.
- Forward scoop on the thruhull
- About 2' of 3/4" hose to the Spectra-provided strainer
- Spectra strainer is direct mounted to the service valve/boost pump
- All strainers and the boost pump are below the water line
- Boost pump to the 5u filter is about 3-4' of hose.
- From the 5u filter onward it's all factory plumbing.
It sounds like you've done everything right on the install. I think the most likely issue you're having is simply the fact that you are running your system in dirty water and the pre-filter is just doing it's job. If you get out on the ocean in nice clean water and you still have the same issue let me know and we can go from there. If you ever motor down here to South Florida let me know and to prove I'm not and old Hen I'll stop by your boat with a new filter and go over your system with you and answer any questions you might have by then, gratis.
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Old 08-07-2012, 06:58   #21
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Quote:
Originally Posted by Tellie
Oh boy, I know I'm starting to sound like an old nagging hen here but I'm really just trying to help you guys.
So a little more clucking about pre-filters.
First, on the idea of dragging filters behind a boat. A Grand Banks is capable of a lot more speed than a sail boat. At cruising speed you'll probably destroy the pre-filter, especially the cheaper ones with cheap inner cores. Not all filters are they same just because they are of the same micron rating. Secondly, a pre-filter can work both ways. They are intended for the water flow direction to be from the outside of the pleated material towards the inside. When you drag a filter behind a boat yes you flush the outside but you also force water through the end of the filter facing the stern through the filters core. That water, at many times the volume and pressure found inside the watermaker, is being filtered in the opposite flow direction because the stopper knot you've tied to the end of the rope blocks the water from exiting, so it has no where to go but through the reverse side of the Pleated filter surface. You are effectively filtering hundreds and hundreds of gallons of water in reverse and coating the inside surface with the same things you are trying to filter out when you run the watermaker. Now you take this filter, put it back into the watermaker and start it up. Now you are estentially back flushing this filter and all the crap you've filtered by dragging it behind the boat directly into the watermakers pump and membrane. This is one of the reasons watermakers do not "back" flush, they instead fresh water flush in a forward direction.
All you really need to do is to gently rinse off the surface with a little fresh water. Never scrub the filter, bleach it, or rinse it under high pressure from a hose nozzle. It will never be white again, but if changed soon enough, you should get 5-8 uses out of it before you throw it away.
Oh there are probably a thousand ways to do the wrong things with filters, but I was not promoting any of those. I was promoting what works so well for 10 years now with our top quality, pleated 25- and 5-micron filters: use a thin piece of line, thread it through the core to tie it into a loop through the filter; tie the other end to the stern of your sailboat, and toss the filter overboard. This works while at anchor as cruisers are 90% + of their time, and it works when bobbing the waves to the next island a bit as long as the line does not get enangled into anything. This does not make the filter to filter in reverse... it thouroughly rinses it and the aggitation loosens up dirt from the filter material, just like washing clothes (as opposed to nly rinsing them). After a day or so at anchor or an hour bobbing waves, get it out, rinse with some fresh and it is ready for re-use.... again and again and again. You will see the material get worse when it's time to replace.

ciao!
Nick.
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Old 08-07-2012, 07:46   #22
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Re: Watermaker pre-filtration and sea water "quality"

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Originally Posted by Tellie View Post
Because yours was a 150 with a lot less flow than a Catalina 300. The 20 will clog up a bit faster, but if you only used a 5 micron in yours (you wouldn't do this because your control was set up a bit different and the pressure sensor design is different) you wouldn't see a big enough difference in how much sooner it would clog up to be worth the effort to add one if it wasn't already there. The higher pressure, flow and boost pump on a Catalina 300 creates a whole different situation. The Catalina 300 is designed to produce a certain amount of product given the design parameters intended. These smaller sized units are built for energy efficiency based partly on the flow. Much older Spectras had three pre-filters, a 50, 20 and 5 Micron. A lot has been learned since then and the design changed to fit the newer systems. The key is as bobconnie points out, watermakers should be run in clean water. If a watermaker is to be cosistantly used in areas that are questionable then a media filter system is a better option, but good ones can get expensive to set up and won't warrant the small savings of a few extra spare filters. Guys, these are Spectras, not some off the shelf pressure cleaner pump units. They are expensive, giving advice on these based on one or two units you've owned in the past is not always a good idea. I can't begin to tell you how many of my calls are from Spectra owners who have a better idea. People can take my free advice here, or I'll be glad to give them my phone number to set up a service call.
OK.

Learn something every day.

Thanks
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Old 08-07-2012, 08:30   #23
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Tellie, by all means cluck on, please. I'm totally new to this and prefer to learn the easy/cheap way rather than the hard way.

I've got the machine running again with one of the filters that we cleaned after it shut down the system a month ago. It started out with one block on the pre filter status screen and 17.5 (I'll have to look up what that number means). After an hour we are at 3 blocks and 14.3, but still making water at 14+GPH.
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Old 08-07-2012, 08:41   #24
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Re: Watermaker pre-filtration and sea water "quality"

Our system is a Village Marine (now Offshore Marine Labs) Baltic that we adapted to use just a single 40 inch membrane (vs 3 x non-standard 38 inch membranes). Adequate for our needs at 25 gph (in warm water). The system requires 10psi inlet pressure from the primary low pressure pump to operate. Provided the prefilters permit 10 psi to reach the secondary high-pressure pump the system makes water. As 2 individuals cruising in the Bahamas, we found that 30-35 gpd was more than adequate for needs. If I were a longer-term, long-distance cruiser, rather than run an oversized system, I would advocate carrying a spare membrane just in case of a problem.
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Old 08-07-2012, 09:07   #25
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Re: Watermaker pre-filtration and sea water "quality"

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"1) How do you visually judge the water clarity to decide whether to operate or not?"
Tree, if you really want to get objective about that, you use a secchi disk, which is easily and cheaply home made.

Secchi disk - Wikipedia, the free encyclopedia

Lower the disk into the water, pay out the line until you can't tell the black from white, now you've got a visibility measurement. In the NE US, the waters are fairly rich with organic matter so the visibility is generally low, often under six feet as compared to a hundred+ in tropical waters. So yes, your filters will clog much more quickly, but then again, the NE US usually offers excellent potable water at little or no cost, versus tropical prices.

You can always plumb in more filters. Perhaps home water filters would be effective enough to take out a lot of the material, you might ask some of the suppliers about micron sizing and then try a cheap internet supplier for them. (Hardware store prices can be 5x higher than web prices.)
Thanks for this great tip, inexpensive way to judge the water quality.
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Old 08-07-2012, 16:20   #26
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Re: Watermaker pre-filtration and sea water "quality"

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Originally Posted by chrisjs View Post
Our system is a Village Marine (now Offshore Marine Labs) Baltic that we adapted to use just a single 40 inch membrane (vs 3 x non-standard 38 inch membranes). Adequate for our needs at 25 gph (in warm water). The system requires 10psi inlet pressure from the primary low pressure pump to operate. Provided the prefilters permit 10 psi to reach the secondary high-pressure pump the system makes water. As 2 individuals cruising in the Bahamas, we found that 30-35 gpd was more than adequate for needs. If I were a longer-term, long-distance cruiser, rather than run an oversized system, I would advocate carrying a spare membrane just in case of a problem.

"Our system is a Village Marine (now Offshore Marine Labs)"
Now Parker Racor

The older VMs were good units, well worth maintaining, and your changing of the membrane vessel to a non proprietary size was a good choice.

But I would not recommend carrying a spare membrane unless it is properly stored and most don't. They usually just keep it sealed in the two bags they come in. Membranes left this way only have a shelf life of about one year or so. If the membrane in your system fails for some reason three years later chances are good that the spare will be worthless.

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Old 08-07-2012, 16:26   #27
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Re: Watermaker pre-filtration and sea water "quality"

Quote:
Originally Posted by s/v Jedi View Post
Oh there are probably a thousand ways to do the wrong things with filters, but I was not promoting any of those. I was promoting what works so well for 10 years now with our top quality, pleated 25- and 5-micron filters: use a thin piece of line, thread it through the core to tie it into a loop through the filter; tie the other end to the stern of your sailboat, and toss the filter overboard. This works while at anchor as cruisers are 90% + of their time, and it works when bobbing the waves to the next island a bit as long as the line does not get enangled into anything. This does not make the filter to filter in reverse... it thouroughly rinses it and the aggitation loosens up dirt from the filter material, just like washing clothes (as opposed to nly rinsing them). After a day or so at anchor or an hour bobbing waves, get it out, rinse with some fresh and it is ready for re-use.... again and again and again. You will see the material get worse when it's time to replace.



ciao!
Nick.

I would not presume to question, Master Yodle,
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Old 08-07-2012, 16:32   #28
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Re: Watermaker pre-filtration and sea water "quality"

Quote:
Originally Posted by twistedtree View Post
Tellie, by all means cluck on, please. I'm totally new to this and prefer to learn the easy/cheap way rather than the hard way.

I've got the machine running again with one of the filters that we cleaned after it shut down the system a month ago. It started out with one block on the pre filter status screen and 17.5 (I'll have to look up what that number means). After an hour we are at 3 blocks and 14.3, but still making water at 14+GPH.
Again, not sure if you're in really great water. But try a brand new filter. Then start the system after about 10 minutes scroll through the control panel to the pre-filter graph. If it still has the first square dark then your problem, a minor one, is in the pressure sensitivity setting. Let me know and I'll walk you through it.
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Old 09-07-2012, 15:47   #29
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Re: Watermaker pre-filtration and sea water "quality"

My test run lasted for 2hrs before calling for replacement of the pre-filter. At that point the inlet pressure was at 9.5.

Tellie, I did your test with a new filter and right from the get-go the filter condition has one block filled in and after about 10 minutes the pressure reads 17.8. I found the section in the manual on this and checked the "Clean Pressure" setting in the MPC and found it was set to 19. So I adjusted it to 17 and will try again once in clear water. I'm assuming this was the adjustment you had in mind, or is there more I should check?

I'm presuming this will get me a little more time on a filter, but I'm coming to believe that this is just life in New England waters. If that's the case, then I'd like to come back to the idea of adding a 10u or 20u filter ahead of the existing 5u. It seems to me like the right thing to do, but I would love insight from the experts. Right now I can only make about 30 gal of water on a filter which isn't very good.
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Old 09-07-2012, 15:59   #30
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Re: Watermaker pre-filtration and sea water "quality"

I do not consider it practical to run a reverse osmosis system in the Northeast, the mid-Atlantic, Chesapeake Bay, or Florida (unless well off-shore). Nowhere on the ICW is clean enough for routine operation. Bottom line it is more trouble than it is worth!! Much easier to fill the tank up at the dock and to try to be frugal when not convenient to fill. We have removed our membrane/housing and filled with sodium metabisulfite solution for long term storage - not sure that is worth the trouble, either. Do njot plan to use the RO again until we hit the Bahamas again. Only other possible use might be in the cold, clear waters of Maine or Canada, though the rate of production drops significantly with lower temperature water. We have used our system 6 months in 6 years so far.
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