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Old 25-12-2016, 05:46   #1
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Bacflushing watermakers with dock water?

The instructions for most, if not all watermakers, indicate dock water should not be used because dock water contains chlorine. Chlorine kills the w/m membrane. However, carbon filters are supposed to remove chlorine, some minerals, and other nasty stuff. So, the question is, does a carbon filter remove enough chlorine to make using dock water safe? Right now, I don't have enough w/m water in the tanks to backslash and I don't want to pickle and unpickle. Anybody have any experience with this?
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Old 25-12-2016, 05:59   #2
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Re: Bacflushing watermakers with dock water?

Depends on the water of course, but Ive used municipal water to flush via a new charcoal filter many times. Got about 8 years out of my last membrane.

If you have access to a test kit then test chlorine level in the water. I would install a new carbon filter (carbon filters are only good for about 6 months after getting wet). And, if the dock water is potable, put it in your tank to dilute with RO water before flushing.

Alternatively dump purchased RO water in your tank.
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Old 25-12-2016, 06:18   #3
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Re: Bacflushing watermakers with dock water?

Why not just make some more RO yourself, then backflush?
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Old 25-12-2016, 07:01   #4
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Re: Bacflushing watermakers with dock water?

I'm in a marina. The water is foul. Wouldn't want to run it right now.
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Old 25-12-2016, 07:18   #5
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Bacflushing watermakers with dock water?

I have bought cheap 10" carbon filters that I believe contain little if any carbon and do next to nothing, they are pleated paper filters with what looks like carbon dust in the paper.
Then I have bought carbon filters that look like plastic tubes filled with carbon chunks, you shake them and hear them rattle, they seem to remove most if not all the chlorine, as long as you run the water through pretty slowly, although I have not tested.
I think I may just buy enough distilled water to do the job and be certain that way?
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Old 25-12-2016, 07:46   #6
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Re: Bacflushing watermakers with dock water?

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Originally Posted by Pitchondesign View Post
I'm in a marina. The water is foul. Wouldn't want to run it right now.
It won't hurt anything to make just a few gallons. Usually, the water isn't nearly as nasty a foot or two below the surface, solids and oils float and your pre-filter will catch the rest. We've done this many times without any harmful effects to us or the system. Just test the water for ppm if in doubt and then divert it into a bucket instead of your tank.
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Old 25-12-2016, 08:34   #7
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Re: Bacflushing watermakers with dock water?

You should really seriously think about adding a simple carbon filter inline to flush your system after each use and every few days or so depending on your location. The carbon filters sole purpose is to remove chlorine from dock water that is introduced to your tanks as you fill them. This is a normal and highly recommended procedure. Make sure you use a good solid block carbon filter for this, not the less expensive granulated filters meant for under your sink at home that can be bought at Home Depot etc. Contact any reputable watermaker company and they will sell you the right one.
That said, I always recommend that if you have a chance to fill your tanks with known good quality dock water that you do so. First you are going to fill your tanks faster than most normal sized watermakers will and secondly, adding the residual chlorine to your tanks from dock water will help keep the growth down in your tanks. RO water contains zero residual chlorine and will not prevent any growth. Never add extra chlorine to your tanks if you are going to use it to flush your watermaker as it is quite easy to over power the charcoal filter and allow too much chlorine past it and burn the membrane. If your tanks go sour you need to clean them out.


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Old 25-12-2016, 09:34   #8
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Re: Bacflushing watermakers with dock water?

Sounds like a good carbon block filter is the way to go. Thanks
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Old 25-12-2016, 09:48   #9
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Re: Bacflushing watermakers with dock water?

Quote:
Originally Posted by Tellie View Post
You should really seriously think about adding a simple carbon filter inline to flush your system after each use and every few days or so depending on your location. The carbon filters sole purpose is to remove chlorine from dock water that is introduced to your tanks as you fill them. This is a normal and highly recommended procedure. Make sure you use a good solid block carbon filter for this, not the less expensive granulated filters meant for under your sink at home that can be bought at Home Depot etc. Contact any reputable watermaker company and they will sell you the right one.
That said, I always recommend that if you have a chance to fill your tanks with known good quality dock water that you do so. First you are going to fill your tanks faster than most normal sized watermakers will and secondly, adding the residual chlorine to your tanks from dock water will help keep the growth down in your tanks. RO water contains zero residual chlorine and will not prevent any growth. Never add extra chlorine to your tanks if you are going to use it to flush your watermaker as it is quite easy to over power the charcoal filter and allow too much chlorine past it and burn the membrane. If your tanks go sour you need to clean them out.


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We do what you suggest for that very reason. But since we're at achorages most of the time and adding RO water daily, we rarely need to flush the system.
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Old 25-12-2016, 14:25   #10
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Re: Bacflushing watermakers with dock water?

A small quantity of sodium bisulfite added to chlorinated water will neutralize the chlorine. One teaspoon per gallon of (city chlorinated) water is sufficient.

Sodium bisulfite is the same chemical commonly used to "pickle" the RO membranes.

Sodium bisulfite powder can be ordered on Amazon or Ebay. It is also available locally at firms that deal in supplies for home brewers and wine makers.

Caution: Some persons are allergic to sodium bisulfite. Mix the powder with the flush water in an open container in a well ventilated area. On deck or on the dock. Do not breath in the powdered chemical under any circumstances. Wear protective gloves while mixing and handling the chemical or mixed flushing solution.

When restarting the RO machine, dump the product water to drain for 10 - 15 minutes to ensure all sodium bisulfite solution has been flushed from the membrane housings.

More information on the use of sodium bisulfite can be obtained from the maker of your particular sea water RO unit.
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Old 25-12-2016, 16:07   #11
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Re: Bacflushing watermakers with dock water?

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Originally Posted by ex-12m-guy View Post
A small quantity of sodium bisulfite added to chlorinated water will neutralize the chlorine. One teaspoon per gallon of (city chlorinated) water is sufficient.

Sodium bisulfite is the same chemical commonly used to "pickle" the RO membranes.

Sodium bisulfite powder can be ordered on Amazon or Ebay. It is also available locally at firms that deal in supplies for home brewers and wine makers.

Caution: Some persons are allergic to sodium bisulfite. Mix the powder with the flush water in an open container in a well ventilated area. On deck or on the dock. Do not breath in the powdered chemical under any circumstances. Wear protective gloves while mixing and handling the chemical or mixed flushing solution.

When restarting the RO machine, dump the product water to drain for 10 - 15 minutes to ensure all sodium bisulfite solution has been flushed from the membrane housings.

More information on the use of sodium bisulfite can be obtained from the maker of your particular sea water RO unit.


A word of caution here, sodium bisulfite will pickle a Spectra membrane just fine, but it will destroy your $3,600 Clark pump and the life time warranty that came with it.
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Old 25-12-2016, 16:30   #12
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Re: Bacflushing watermakers with dock water?

Agreed, ive done this many times.

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Old 26-12-2016, 10:22   #13
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Re: Bacflushing watermakers with dock water?

Something that should be mentioned is the efficiency of carbon filters. I believe the Spectra element removes 97%, while your Home depot carbon filters are somewhere around 60%.
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Old 26-12-2016, 15:33   #14
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Re: Bacflushing watermakers with dock water?

Where do you get data for the chlorine removal efficiency?
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Old 26-12-2016, 16:45   #15
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Re: Bacflushing watermakers with dock water?

This took me about 30 seconds to find...

Activated Carbon Filter

Carbon Filtration: What It Does, What It Doesn't –*Pure Water Products, LLC

Activated Carbon Water Filters and Purification (Granular/GAC and Carbon Block

I attended Spectra's technical classes. They told me theirs was 97%. The first site I supplied has a slightly higher rating. The ones from Home Depot I use for drinking water state 60% on the packaging. Hope this helps.
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