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Old 19-07-2016, 23:26   #1
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Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER tank

This is to create bottled water quality drinking water from the boat freshwater tank on a separate tap in the galley.

I know these units reject the excess water in homes down the drain, however it is still fresh water and probably just fine for normal use, I could return the reject to the 300 gallon tank or return it to a separate tank if necessary.

Any thoughts on this.

Remember, I am NOT trying to make fresh water from Salt, just clean up freshwater tank water for drinking.

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Old 19-07-2016, 23:38   #2
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Re: Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER ta

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Originally Posted by botanybay View Post

Remember, I am NOT trying to make fresh water from Salt, just clean up freshwater tank water for drinking.
Waste of time & effort.

Just keep your system clean to begin with.
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Old 19-07-2016, 23:53   #3
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Re: Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER ta

Wasn't there some kind of issue with running clean water through a watermaker? As in damaging the membrane or something? Or was it about water with any chlorine in it?
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Old 20-07-2016, 00:09   #4
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Re: Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER ta

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Wasn't there some kind of issue with running clean water through a watermaker? As in damaging the membrane or something? Or was it about water with any chlorine in it?
I am not suggesting using a water maker designed for salt water.

There are under sink water purifiers which use reverse osmosis at much lower pressure to make a couple of gallons of purified water overnight.

Because the reverse osmosis is fresh water to fresh water I suspect the required pressure is compatible with household water pressure.



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Old 20-07-2016, 00:31   #5
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Re: Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER ta

You're idea is a silly waste of money IMHO. Just clean up your existing tank and plumbing system and then run your tap water through a Brita pitcher before consumption. Total cost: About $12

A low pressure reverse osmosis scheme sounds more like hocus pocus, feel-good about yourself snake oil voodoo. There's no way it can do what it claims without high pressure forcing water molecules through a true membrane.
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Old 20-07-2016, 01:29   #6
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Re: Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER ta

So basically you want to use a home RO water purifier on your boat's fresh water, non? If so, looking up the pressures shouldn't be much tougher than digging around the manufacturer's website. So I'm not seeing where the complication comes from, or the difficulty in finding information. Can't any Home Depot, or Lowe's field the question?

Also, such a unit, designed for home use, might be slightly more adept at filtering out some sanitizing chemicals. Since most city water treatment plants use chemicals to make their water safe to drink. But that's an educated guess about such filters on my part.
They do seem to make good water though. Or at least such has been the case with the one's I've sampled.

What units specifically are you looking at?
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Old 20-07-2016, 01:53   #7
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Re: Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER ta

Yeah the waterboard put chlorine in your drinking water to make it safe to drink and flouride cause its good for your teeth........I was only thinking the same question about filtering my tanks for bottle quality water.. Its only a stupid idea if you believe chlorine and flouride are good for you. Your body is saturated with oxygen depleting chlorine and flouride decays bones..
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Old 20-07-2016, 04:44   #8
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Re: Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER ta

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Originally Posted by Kenomac View Post
You're idea is a silly waste of money IMHO. Just clean up your existing tank and plumbing system and then run your tap water through a Brita pitcher before consumption. Total cost: About $12

A low pressure reverse osmosis scheme sounds more like hocus pocus, feel-good about yourself snake oil voodoo. There's no way it can do what it claims without high pressure forcing water molecules through a true membrane.
There are several different style membranes. Filmtec makes a TW membrane for fresh or tap water usage, with a 40-50psi working pressure up to say 1,000 TDS on the small household units. BW for brackish water requiring pressures from 250-600 psi, and of course SW membranes that we are all use to seeing. All made from the same Polyamide membrane materials.

You must remove chlorine from the water prior to it getting to the RO as chlorine is a killer of TFC (Polyamide ) membranes. There are also CA cellulose acitate membranes that are for chlorinated water, and even CTA (cellulose tri- acitate ) membranes that are either or, but they do not perform near as well as the TFC PA membranes do which is why they are the membrane most use.

Running the concentrate from the RO back into your tank will significantly raise the conductivity (TDS) in your tanks and if the OP's thinking is reusing the reject (concentrate) water over and over again, it won't work as it will raise the feed water TDS to the point where you wont make any water. Also, these small household RO's work on a 25-30% recovery rate which means you are wasting 3-4 gallons of water to make 1.
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Old 20-07-2016, 04:55   #9
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Re: Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER ta

Why not a single ... or double chambered filtering system?

I would think the water pressure needed, would be less.

I'm setting up a Filtrete, universal refrigerator system ... 0.5 microns sediment filter to remove chlorine and Guardia cysts ...

I suspect the water flow will be reduced, but hey ... I got time
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Old 20-07-2016, 05:09   #10
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Re: Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER ta

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Originally Posted by botanybay View Post
This is to create bottled water quality drinking water from the boat freshwater tank on a separate tap in the galley.

I know these units reject the excess water in homes down the drain, however it is still fresh water and probably just fine for normal use, I could return the reject to the 300 gallon tank or return it to a separate tank if necessary.

Any thoughts on this.

Remember, I am NOT trying to make fresh water from Salt, just clean up freshwater tank water for drinking.

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I'm thinking you want to insure as much as is possible that you have quality drinking water from your taps. First, when the water tank is very low on water, add a good amount of bleach (1 cup) to it and starting at the faucet furthest away, run it until you smell the bleach. (wont take long). then do the same to the other faucets and taps. Then run the remainder through the hot water side (if you have it) and completely drain your tank. Let sit overnight and flush either with freshly loaded water in the tanks, or preferably from a shore water connection. This will sanitize your boats entire water system. I'd install a 10" carbon block filter 5 micron after the FW pump so all water goes through it that enters the boats water lines and then add a very little amount of bleach (cap full) to the FW tank every time you fill it. Buy yourself a cheap little pool test kit to check the chlorine with if you want and keep it at 1 ppm free chlorine. on just the line feeding say your kitchen sink, you could install a small silver impregnated ceramic filter or even another carbon block with a 0.5 micron rating that would give you very high quality water for drinking.
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Old 20-07-2016, 05:17   #11
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Re: Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER ta

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Originally Posted by SURV69 View Post
Why not a single ... or double chambered filtering system?

I would think the water pressure needed, would be less.

I'm setting up a Filtrete, universal refrigerator system ... 0.5 microns sediment filter to remove chlorine and Guardia cysts ...

I suspect the water flow will be reduced, but hey ... I got time
Giardia Lambia is caused by deer and beaver droppings in streams and open water sources. Not wells or from bio growth. Don't over think your water system. Chlorinate for killing bacteria, and remove the bleach after the tanks. Keep it simple
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Old 20-07-2016, 06:08   #12
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Re: Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER ta

I agree with the others, don't over think or engineer this. Keep your tanks as clean as you can, no one has perfectly clean tanks, be careful with chlorine, and add a point of use filter to the tap you intend to consume water from. Simple and easy.

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Old 20-07-2016, 06:22   #13
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Re: Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER ta

Quote:
Originally Posted by botanybay View Post
This is to create bottled water quality drinking water from the boat freshwater tank on a separate tap in the galley.

I know these units reject the excess water in homes down the drain, however it is still fresh water and probably just fine for normal use, I could return the reject to the 300 gallon tank or return it to a separate tank if necessary.

Any thoughts on this.

Remember, I am NOT trying to make fresh water from Salt, just clean up freshwater tank water for drinking.

Sent from my SM-G935V using Cruisers Sailing Forum mobile app

I see no problem with doing it if your system can supply the inlet requirements and unlike others see no reason for you to feel foolish by thinking about it or doing it. I would bet the reject going back to the tank isn't a problem due to the low percentage, but the volume is low probably just as well to dump it.
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Old 20-07-2016, 06:48   #14
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Re: Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER ta

Under sink RO salesman came to my house (years ago). Wanted to sell me a system for a coupla grand.

He pulled out his test kit and tested my water for TDS and voila!, the TDS was high (California city water - go figure).

He had a filtration system with him. I asked him to hook it up and show me how effective it was...by doing a TDS test on the filtered water after hook up and flushing.

"That'll take too long!"
"No one has ever asked my to do that!"

I refused to talk to him unless he hooked it up.

We hooked it up, flushed, and tested for TDS.

TDS was unchanged by his system.

No sale was made that day.
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Old 20-07-2016, 06:49   #15
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Re: Anyone used an under sink reverse osmosis unit to purify water FROM FRESHWATER ta

No reason not to if you really want to, but I see no reason a good high quality carbon filter with colloidal silver in it won't do everything you want it to.
My boat came with the seagull system, seems to work well, but may cost more than it's worth, I think you can get at least as good, for much less money, but as it was already there, I popped for the stupid expensive filter, and a couple of years later it's still fine.

What I do and it seems to work well is to filter the water going into the tank with a 10" high quality charcoal filter that removes chlorine and filters to 5 micron, then as I have 30 yr old aluminum tanks that have a lot of lime in them, I have another of the same filter on the output side of the pressure pump, then any water we use for drinking and cooking goes through the Seagull, probable overkill, but it does give bottle quality tasting water.
Reasoning for filtering going into the tank is it's aluminum and 30 yrs old, any chlorine would surely react with the aluminum, weakening it even further, post filter is to remove the hard water deposits that have built up over the last 30 yrs and flake off and come out, you really see it when doing a passage with significant weather and a half full tank.
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