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Old 08-05-2018, 10:14 AM   #1
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Plumbing water filters backwards

I have a dumb question regarding water filters......

We use copious amounts of fresh water on board (two dogs, fresh water flush, showers, etc.) so make water daily. In the PNW there is lots of algae so the supply water to the water maker goes through a 50 mesh stainless algae filter, then a 20 micron spun filter, then the 5 micron pleated filter the manufacturer requires. In replacing these (they last anywhere from 4 to 8 days), I see that the water flows into the middle of the cartridges, then out. This makes them tough to clean and re-use since getting the gunk out of the inside of the filter is harder than if the crud were on the outside.

Is there any reason not to plumb these filters backwards, so the flow is from the outside of the filter to the inside? I can't see one, but there may be a reason. Anyone know the answer?
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Old 08-05-2018, 12:56 PM   #2
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Is the current canister marked w inlet & outlet or is thatjust the way its plumbed?
And home or RV filter housing/cartridge I've seen flows outside to inside. The larger area outside has a lower velocity due to the larger area than inside and helps settle out and larger particles.
I cant think of a reason it could hurt anything if it is a cartridge type filter.
through hull strainers on the other hand flow inside to out but they are just a bssket strainer and contain the junk when pulled to clean.
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Old 08-05-2018, 12:58 PM   #3
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That's odd. I always thought the correct flow was from the outside of the filter to the inside. In other works, like you are proposing. I just checked a Pentair Big Blue filter housing that I have kicking around and it does indeed flow from outside to inside, with inlet and outlet clearly marked to ensure that flow direction.


Are your filter housings marked for inlet and outlet? It sounds to me like they are installed backwards, and your proposed change would set them right.


Related to this, I found that adding a media filter was the key to makermaker use in the PNW, and NE as well. After installing a media filter, I only changed the 20 and 5 micron pleated filters once a year as routine maintenance. Nearly all debris was caught in the media filter, and you just backwash it to clean it. No more changing filters and spilling salt water everywhere.
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Old 08-05-2018, 12:59 PM   #4
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We use a combination particulate/carbon filter in a standard 10” housing. It’s a radial flow cartridge; outside to inside flow direction which I think is standard for pleated filters. Maybe yours is plumbed backwards now?
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Old 08-05-2018, 01:02 PM   #5
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Originally Posted by Bacchus View Post
Is the current canister marked w inlet & outlet or is thatjust the way its plumbed?
And home or RV filter housing/cartridge I've seen flows outside to inside. The larger area outside has a lower velocity due to the larger area than inside and helps settle out and larger particles.
I cant think of a reason it could hurt anything if it is a cartridge type filter.
through hull strainers on the other hand flow inside to out but they are just a bssket strainer and contain the junk when pulled to clean.



Good point. The mesh filter would flow inside to outside so debris collects in the basket and can be easily removed. But the pleated filters should flow outside to inside.
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Old 08-05-2018, 01:59 PM   #6
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Typically the flow is outside to inside. One reason is that the filter material is supported by the central core with the pressure being outside to inside.
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Old 08-05-2018, 02:38 PM   #7
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Which filter canister and media filter did you use?
Thanks
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Old 08-05-2018, 03:03 PM   #8
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Which filter canister and media filter did you use?
Thanks

Here's an article on the retrofit Adventures of Tanglewood: Water Maker Media Filter Take a look, then happy to answer questions. I would never install a watermaker without one. It transformed the machine from a source of frustration to a very useful tool.
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Old 08-05-2018, 03:16 PM   #9
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Normally, on a standard pleated filter, flow is out to in. One special type of filters we use on our watermakers is a "bag" filter, and flow is in to out, so the bag catches the debris. We like this type for high turnover filters because they can store flat in a much smaller space.
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Old 08-05-2018, 05:18 PM   #10
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I use 4.5x20 housings and have 20, 5, and 1 micron filters. The 20 and 5 are washable and get cleaned about twice a year. The 1 micron lasts about a year. I live aboard and make all of my water (don't use marina water), have laundry and dishwasher, so a lot of water goes thru the filters.
And the filters are plumbed to pass water from the outside to the center.
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Old 08-05-2018, 08:52 PM   #11
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Originally Posted by twistedtree View Post
That's odd. I always thought the correct flow was from the outside of the filter to the inside. In other works, like you are proposing. I just checked a Pentair Big Blue filter housing that I have kicking around and it does indeed flow from outside to inside, with inlet and outlet clearly marked to ensure that flow direction.


Are your filter housings marked for inlet and outlet? It sounds to me like they are installed backwards, and your proposed change would set them right.


Related to this, I found that adding a media filter was the key to makermaker use in the PNW, and NE as well. After installing a media filter, I only changed the 20 and 5 micron pleated filters once a year as routine maintenance. Nearly all debris was caught in the media filter, and you just backwash it to clean it. No more changing filters and spilling salt water everywhere.
Yep, they are marked and it goes from inside to outside. GE smart filter housing. Weird.
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Old 08-06-2018, 06:41 AM   #12
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Originally Posted by Delfin View Post
Yep, they are marked and it goes from inside to outside. GE smart filter housing. Weird.

Yes, odd indeed. Does it use standard filter cartridges? 2" x 10", or 4.5" x 10"?
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Old 08-06-2018, 08:11 AM   #13
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Yes, odd indeed. Does it use standard filter cartridges? 2" x 10", or 4.5" x 10"?
They're 2 x 10. I checked another 4.5 x 10 on the house water and it is plumbed out to in, but these are definitely the reverse. In any case, the answer to my question is that it doesn't matter, since some housing do it one way, and others another.

I really like your use of a media filter, Peter. I used to use those in irrigation systems where the supply was from wells. I just wish I had room for one, but they all seem too big. I might fab one up though. We always used sand, as I recall, for the media, but the Parker material clearly is superior.

Did you (or anyone) ever consider a booster pump upstream of the filters? I get around 700 gallons out of a 5 micron filter in the PNW with a 20 micron string wound filter before that, but if a suitable pump could be found, I would expect to get double that since when I remove a filter, in most cases there is still quite a bit of surface area that is capable of filtering a bit more.
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Old 08-06-2018, 11:36 AM   #14
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Mystery solved. Some idiot mislabeled the inlet with the outlet line, so when I added an algae screen and 20 micron pre-pre-filter, I plumbed what I thought was the inlet to the correct inlet port on each housing. Unfortunately, since this was actually the outlet, the filtering sequence was 5 mic, 20 mic, then a 50 mesh screen, which somewhat defeats the purpose of sequential filtering.

We shall ignore for the moment that the idiot who mis-labeled the lines was me, but thank you all for helping me get it right. The second time. It's worked fine for years in this bass ackwards configuration, and hopefully will work even better now.
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