Adding Bleach to RO Water

[Chotu]

Originally Posted by sailorboy1

As the OP I guess I need to just give up on the thread. For some reason it has become a “how to disinfect a water tank”

Frustrating, isn’t it? Happens to mine constantly.

Simple answer is don’t backflush with chlorinated water. However you stuck to that is your choice.

[VChild]

Originally Posted by sailorboy1

As the OP I guess I need to just give up on the thread. For some reason it has become a “how to disinfect a water tank”

Since installing my watermaker I’ve struggled with the same question. I had always wondered whether the carbon filter would get all the chlorine out of the water that was used for flushing the watermaker. Until I find a better way, I have plumbed my system with a valve that can divert freshly made water straight from the watermaker to the galley sink where I can quickly fill a few jugs of drinking water. Otherwise the valve is turned to fill the tanks. I don’t add chlorine to the tanks for several reasons. First, they are used to flush the watermaker. Second, the water is not used for drinking but just showering, washing and freshwater toilet flushes etc. Third, my turnover of water in the tanks is fairly quick so they don’t have time to grow anything. I’m not living aboard so filling a few drinking water jugs doesn’t bother me.
I have a dedicated drinking water faucet at the galley sink (skinny faucet in the picture).

https://www.youtube.com/watch?v=-VsMlxH0jE4

[sailorboy1]

I will install a second carbon filter in series with first if that is what it takes. Overall that will be a lot less trouble than making buckes of water for flushing. Sometimes I have to flush the system without having used it to make water.

[VChild]

Originally Posted by sailorboy1

I will install a second carbon filter in series with first if that is what it takes. Overall that will be a lot less trouble than making buckes of water for flushing. Sometimes I have to flush the system without having used it to make water.

Yeah I can see where that would be an issue staying long term in a marina or harbor where you wouldn't want to run the watermaker. When I cruise I don't spend much time in marinas. I like your idea of two filters. Maybe even in parallel where you could switch from one to the other when the chlorine tests too high.

[contrail]

Originally Posted by sailorboy1

For same reason you add it to any water

I never add bleach. Too tough on too many things.

[CarlF]

Again. If you are using bleach in a water tank simply have a pack of pool test strips.

Test the water before flushing. I always see it back at 0 ppm just 24 hours after adding a bit of bleach. Of course, still run it through a chlorine killing filter to be safe.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[Paul L]

SB,
On flushing the WM with light chlorinated water, as long as your carbon filter is relatively new it should not be any issue. I believe Spectra states a 6 month calendar life for carbon filters.

As far as chlorinating WM water, I don't see the advantage. The source water does not contain any significant bacteria or virus. So anything picked up will be in the pipes, tanks, vents. Doing a good chlorine shock of the water system as needed should leave you with a plenty clean system.
Of course that begs the question, when is as needed. We normally (non Covid season) only put WM water in our tanks. In this case we only shock the system if the water system has not been used for an extended period. In practice that's usually once every year or two.

[buckleykr]

We flush the water-maker with whatever water is in the water tank at the time. On the edges of the sailing season this will be city water. In the middle of the sailing season this will be water-maker water. We replace the carbon filter used for the flush water each spring and winterize the water-maker each fall. I don't worry about it. Membrane is ~10 yrs old. I've never done a bleach treatment to the tanks. Inspected them last spring and there was nothing evident in them. They are SS. Presumably the fill-ups with city water have enough chlorine (or ??) to keep them clean.

[Andrea7413]

I work in modern separation technology as a career with membranes being my area of concentration. There are many different types of membranes that are used in water treatment/food technology. Low pressure membranes such as microfiltration and ultrafiltration membranes can be made of different materials, the type most often used in food processing/water treatment are spiral wound and the material they are constructed of is chlorine (sodium hypochlorite) resistant although exposure to oxidizers such as chlorine will affect pore integrity over time. The high pressure membranes such as nanofiltration, and reverse osmosis filtration (water maker filters), the spiral wound variety, are not compatible with chlorine. Concentrations as low as 3-5ppm can damage the pore size of the membrane surface allowing volatile organics thru the membrane into the permeate side which would contaminate your drinking water. When passing chlorine treated water thru the water maker activated carbon should be used to treat the water and the water should be tested prior to passing it thru the water maker to ensure the chlorine has been removed.

All water in water tanks derived from a water maker should be treated with chlorine if the water is not immediately utilized. A concentration of 3-5ppm is sufficient in treating water maker water to prevent biological contamination. At that level it is safe to drink directly but an activated carbon filter will remove the chlorine and improve the taste prior to drinking. Typical chlorine (Clorox) is around 5% sodium hypochlorite, to reach a concentration of 5ppm you would add 1oz (28ml) per 80gal of water.

[OrinocoFlo]

Seems very silly to me to be adding chlorine to watermaker water, which is basically the same thing as bottled water purchased from the store. Do you advise adding chlorine to bottled water? After living half the year for over ten years on RO water, we’ve never added anything and have had zero problems. The tanks get a good cleaning every five years or so and thats it, and we use a Britta pitcher to get rid of the tank taste.

[Andrea7413]

Originally Posted by OrinocoFlo

Seems very silly to me to be adding chlorine to watermaker water, which is basically the same thing as bottled water purchased from the store. Do you advise adding chlorine to bottled water? After living half the year for over ten years on RO water, we’ve never added anything and have had zero problems. The tanks get a good cleaning every five years or so and thats it, and we use a Britta pitcher to get rid of the tank taste.

No membrane surface is 100% uniform, unintended molecules will always get thru, albeit in very small concentrations, over time biofilms will form. Biofilms are stubborn and pernicious critters that will form in most water systems even those that are RO and UV filtered. Tanks and tubes that sit for days without turbulent flow are susceptible to biofilm formation. Oxidizers such as chlorine are great at breaking down organics including the polysaccharide layer in biofilms that protect them from most chemical interventions.

[Paul L]

Originally Posted by Andrea7413

No membrane surface is 100% uniform, unintended molecules will always get thru, albeit in very small concentrations, over time biofilms will form. Biofilms are stubborn and pernicious critters that will form in most water systems even those that are RO and UV filtered. Tanks and tubes that sit for days without turbulent flow are susceptible to biofilm formation. Oxidizers such as chlorine are great at breaking down organics including the polysaccharide layer in biofilms that protect them from most chemical interventions.

And if you periodically shock the system with chlorine these films will not build up. No need to add chlorine to your tank daily or when you make water. I've certainly never met an active cruiser that has gotten sick drinking water maker water.

[Andrea7413]

Originally Posted by OrinocoFlo

Seems very silly to me to be adding chlorine to watermaker water, which is basically the same thing as bottled water purchased from the store. Do you advise adding chlorine to bottled water? After living half the year for over ten years on RO water, we’ve never added anything and have had zero problems. The tanks get a good cleaning every five years or so and thats it, and we use a Britta pitcher to get rid of the tank taste.

Bottled water comes in many forms, distilled water will contain many volatile organics that have a lower boiling point than water. RO water will contain "ash" which is ions that are are smaller that the diameter of a water molecule; magnesium, calcium, etc. The "tank taste" you remove thru your Britta is more than likely a biofilm buildup. Tanks should be treated regularly and cleaned more often than five years.

[nonav]

Please be careful with powdered chlorine.

If water gets on the powder, it can eventually start a fire.

[noelex 77]

We have never used chlorine, and yes, I think it is a potential hazard to the membrane. While the carbon cartridge should keep the membrane safe, it is not unusual for the 10 inch filters to not seal correctly at the top or bottom and it would only take one instance to degrade or destroy the membrane.

For our new boat we installed a small stainless steel day water tank. The watermaker product water feeds into this tank before spilling over into the main tank. The watermaker takes its rinse water from this same tank. Thus disinfectant or “municipal water” can be used in the main tank without risking the membrane. The day water tank also supplies better quality drinking water via its own faucet in the galley.

However, rainwater collection supplies all our current water needs so we have had no need for “municipal water”, or a watermaker.