Watermaker pre-filtration and sea water "quality"

[twistedtree]

Well, I'll be in those cold clear waters of Canada and Maine for the next month. Seawater temp is about 48 deg, up from 36 deg the other day.

I would never even try it in the ICW, Chesapeake, or Florida. They are just too shallow and silty. But a mile or two off the shore of Maine, Mass, and RI the water is pretty darn clear and I would hope I can find a reasonable way to use the watermaker there. I realize Long Island Sound was probably pushing it, as was Buzzards Bay.

[settingsun]

In the Sea of Cortez, Mexico, we could get 1800 gallons of water (30 hours) out of a pair of filters (20 micron followed by 5 micron). On mainland Pacific Mexico we could get as little as 240 gallons (4 hours) when there were remnants of a a red tide running despite going 15 miles out of our way offshore to avoid it...

We just look at the filters and when they are a dark green it's time to change them out.

[CarlF]

To my earlier comment, I have found that my Spectra fouls more quickly in coastal Maine (several miles offshore not up the rivers) than it does in southern NE waters or even farther south. The same thing happened to a friend. I don't understand it, Maybe someone here does.

Carl

[twistedtree]

After changing to a new filter and resetting the "clean filter" pressure, I got 6 hrs of run time before the filter plugged. I think the system is just working the way it is supposed to, and there is enough plankton and other life in the water to plug it up. Given this, I'm planning to add an additional 10u pre-filter to capture larger quantities of plankton (or whatever). Most watermakers seem to have this setup right from the factory, but not the Catalina, perhaps for cost saving reasons. I'd welcome advice on this addition. Here's what I'm thinking so far:

- 4x10 filter rather than a 2x10. A bigger filter will hold more crap before back pressure becomes excessive. That said, I need to look at the cost of the smaller vs larger filter elements to confirm it makes economic sense.

- 10u, and if I find it's still plugging too fast I might switch to 20u. I've been looking at the size of microscopic sea life and I think 20u or even 50u will catch it all, but I need to double check that.

After I add the filter I'll need to reset some of the control parameters, but i don't expect that to be a problem.

Any thought from them who knows?

[chrisjs]

I would go straight for the 20 micron. Filtration is not a linear function. A 20 micron pleated filter will become more efficient at collecting smaller particles as it operates until it ultimately plugs up. Then you can back-flush a few times with non-chlorinated fresh water or seawater before giving up completely. Our system came with 20 micron filters. They need changing about 5x more often than the 5 micron that follows. You can easily buy "Big Blue" 4inch x 10 inch pleated Watts filters on line for about $10 each. Check out Filterfast.com.
Chris

[Cruisingscotts]

This what we did at work, ours is a 350 Ton unit with 20 mic then 10 mic filtration. Over the last several years the algae blooms have gotten pretty bad causing super high filter consumption. We installed large basket strainers on the supply water and purchased a roll of 50 mic filter material from mcmaster Carr, it comes by the yard and is cheap. Just cut out a rectangle to fit inside of the basket. These are easily cleaned multiple times and re-used. I plan on a similar setup for my boat groco and others make nice SS basket strainers, you need a fairly decent sized one to compensate for the restriction.

[twistedtree]

This problem persists. I'm now in the bahamas with crystal clear water and i still only get about 10hrs (130 gal) out of a 5u filter. I did install a 4x10 20u additional pre filter and reset the Clean Filter pressure on the MPC 5000.

This really isn't a very useable watermaker, and I have to believe the problem is specific to my system. I head of people running for 2-6 months on a set of filters, where i get only 10hrs? WTF?

When things plugged up yesterday I tried swapping only the big 20u filter to see what happened. There was no improvement in the boost pressure indicating that it's the 5u that's plugged, not the 20u.

Help?

Since is is an older thread, here's a reminder on the system.

Its a Spectra Catalina 300 MKII with MPC 5000 controller.

[Cruisingscotts]

It's called Climate change, drastic changes in the amount of plankton and algae in the water everywhere. 5 microns is probably more than you need going in. If you use 20 micron followed by 10 or 5 micron you willowy likely get a 2 or 3 to one wash ratio on the 20's and having to change to 5 or 10.

At times in the Bering sea we are changing pre-filters every 10 to 15 min. Just because the water looks clear does not mean it is.


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[senormechanico]

Originally Posted by Badsanta

Call stectra. I have talked to spectra owners and they would replace the filters with new and then clean the old. They would reuse them. and would have one clean and ready one in clean water and one dring and would just cycle them around

I've done exactly that for 15 years with my Spectra 180 with no problems.

[senormechanico]

Originally Posted by Tellie

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.

I've been backflushing with a non chlorinated domestic water supply, alternating filters and laying the recently rinsed one in the sun for a few days. It seems to be working just fine.
My factory updated 180 makes about 8+ gallons per hour at around 100 ppm from battery voltage with no engine, only (maybe) solar input.

Am I going to hell for that?

[s/v Jedi]

Use pleated filter elements. Then replace the filters and rig a line through the center of the dirty filters, tie it to the boat and throw the filters overboard for cleaning cycle. Back aboard I rinse with fresh. When they are very dirty, I add a little bleach to the bucket and soak them until clean and white. Then rinse and dry. They must dry completely because you need to get rid of the chlorine before re-installing them.

Pleated filters can be cleaned 3-5 times.

[belizesailor]

Originally Posted by twistedtree

This problem persists. I'm now in the bahamas with crystal clear water and i still only get about 10hrs (130 gal) out of a 5u filter. I did install a 4x10 20u additional pre filter and reset the Clean Filter pressure on the MPC 5000.

This really isn't a very useable watermaker, and I have to believe the problem is specific to my system. I head of people running for 2-6 months on a set of filters, where i get only 10hrs? WTF?

When things plugged up yesterday I tried swapping only the big 20u filter to see what happened. There was no improvement in the boost pressure indicating that it's the 5u that's plugged, not the 20u.

Help?

Since is is an older thread, here's a reminder on the system.

Its a Spectra Catalina 300 MKII with MPC 5000 controller.

Very unusual. I get a full season out of mine and have for 14 seasons now.

Dont like the idea of the single 5u on the newer Catalinas. My older Catalina 300, has three filter elements in line (50, 20, 5). Much more robust configuration. I've never had this configuration clog and shut down the system. The 50u pre filter is in a clear housing for easy inspection and is easy to access to clean/replace. I may have to clean/replace it once or twice in a whole season, but have never had to touch the finer downstream filters. I change all the filters for new each cruising season.

Also, the pressure sensors are very reliable but can get out of whack. I've had one go bad in 14 years. If you haven't already then test to make sure the pressure/vaccum they are reading is rational. A good old mechanical gauge or two in the system helps with this.

Could be a clog or obstruction somewhere that is causing higher vaccum and thus when the filter gets even a little dirty it throws an alarm. This sounds highly plausible to me.

[SV THIRD DAY]

Originally Posted by Cruisingscotts

It's called Climate change, drastic changes in the amount of plankton and algae in the water everywhere.

I've heard it all now...my kids even fried the Climate Change excuse when I asked them why no one took the trash out of the dinghy...

[Therapy]

Originally Posted by SV THIRD DAY

I've heard it all now...my kids even fried the Climate Change excuse when I asked them why no one took the trash out of the dinghy...

GOOD ONE!

[Scott Berg]

We use a 50u 4x10 pre filter followed by a 20u and a 5u
He big 50 really helps

We refuse paper filters after cleaning them... To clean we tow them behind us in clean ocean water then sun dry

Helps save on filters

S


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