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Seawater into freshwater tank via thru-hull overflow tube
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thataway



Joined: 02 Nov 2003
Posts: 20778
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Mon May 16, 2016 1:06 pm    Post subject: Reply with quote

Harvey, If I understand correctly you say that the "vent tube" for the C Dory 22 water tank is inside of the cabin. All of the C dory's I have owned, including two 22's have the water overflow on the outside of the hull. There is a "Water level" tube on the inside of the cabin,. but that is not a vent tube.

Cschwankl how are you going to vent the tank, if you don't have the outside overflow? We have never detected any salt water contamination of our water tanks, in any of the small boats we have owned except when we were sailing across the Atlantic and the water tank vent was under water as we were heeled over for prolonged time at over 45 degrees and we used water out of that tank, creating a vacuum to pull in salt water!) I later re-routed the vent to the side of the pilot house, from the side of the hull)

Marco, The links is for "EPA registered (food contact) Hard surface" wipe down.
http://www.education.nh.gov/instruction/school_health/documents/disinfectants.pdf

Not for water tanks. EPA continues to recommend 50 PPM using 8.25% or 5.25% sodium hypochlorite bleach for decontamination. Let sit--We usually use 6 hours, but up to 48 hours, and then rinse several times, until there is no further Cl smell.
Table for using 5.25% bleach (non scented):
For treating unknown clear water: Double for cloudy water.
Approximate measurements:
8 drops per gallon: i drop = 0.017 oz (about 5 ppm)
For 10 gallons a Teaspoon (0.16 oz)~5 ppm, 3 teaspoons=50 ppm
for 25 gallons, 1/2 Tablespoon (0..25 oz) = 5 ppm, 4oz = 50 ppm (Tablespoon = 0.25 oz


We drink water out of our water tanks. (This is why we can go 10 days at Powell with the 20 gallon tank, and a back up of 5 gallon in a plastic container.) Marie dose use the Brita filter. I don't care if it is filtered or not.

We do use 8.25% of sodium hypochlorite at the end of season, and pump the line dry. Before a trip, we usually flush the tank with a 50 PPM solution. (put in about half water, then add the bleach, then the rest of the water.

EPA:
Quote:
The EPA requires treated tap water to have a detectable level of chlorine to help prevent contamination. The allowable chlorine levels in drinking water (up to 4 parts per million) pose “no known or expected health risk [including] an adequate margin of safety.” Only chlorine based disinfectants can provide lasting protection from waterborne diseases throughout the distribution system from treatment plant to the consumer’s tap.
Most home water contains about 1 ppm of chlorine.

H2O2 comes in many concentrations. Usually drug store starts out at 3% or 6%. When H2O2 is used in waste water decontamination it is higher concentration or 50% or so (not stable, and requires specialized handling). Although you might use H2O2 to clean surfaces, I would not recommend it for regular use as treatment. The contact time and concentration will not be adequate.

Here is EPA's take:
Quote:
Hydrogen peroxide (H2O2) is rarely used in drinking water treatment as a stand-alone treatment process. H2O2 is a weak mirobiocide compared to chlorine, ozone, and other commonly used disinfectants. Consequently, it is not approved by regulatory agencies as a stand-alone disinfection treatment process. However, there are a number of technologies where H2O2 is used as part of the treatment program. The advanced oxidation process (AOP) uses H2O2 in conjunction of O3 and/or UV light to produce hydroxyl radicals (·OH), which are very effective in removing taste and odor (T&O) compounds, and inorganic and organic micropollutants. H2O2 can also be catalyzed with iron, to produce hydroxyl radicals by Fenton's reaction. Addition of H2O2 in conjunction of UV light and/or ozone produces powerful hydroxyl radicals, which are more effective than ozone or UV alone. AOP involving hydroxyl radicals in drinking water treatment is used to remove various persistent organic and inorganic micro-pollutants. O3/ H2O2 and UV/ H2O2 have been successfully used to oxidize many persistent pesticides, T&O compounds, pharmaceutical and hazardous chemicals that may be present in surface and groundwater.
In the Fenton process, H2O2 and iron generate hydroxyl radicals through a catalytic process. The process is based on electron transfer between H2O2 and iron ions. The hydroxyl radical produced during this activation process is a strong oxidizing agent able to oxidize organic compounds. The advantage of this process is that no energy input is necessary to activate the hydrogen peroxide. However, the main disadvantage of this process is the additional water pollution caused by adding the iron salt. Solid iron blocks have been used to avoid water pollution with iron salt; however, leaching of metal ions makes this process problematic. Fenton's Reagent has proven to be very effective in the treatment of organic molecules. However, the process is expensive because additional residuals, which require disposal, are generated and a continuous supply of feed chemicals is required."

_________________
Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
KA6PKB
Home port: Pensacola FL
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Sunbeam



Joined: 23 Feb 2012
Posts: 3990
City/Region: Out 'n' About
State or Province: Other
C-Dory Year: 2002
C-Dory Model: 22 Cruiser
Photos: Sunbeam
PostPosted: Mon May 16, 2016 2:19 pm    Post subject: Reply with quote

I've also always drunk out of the onboard water tanks (on various boats). There wouldn't really be any other practical way to do it when cruising (previous boats). If I had a tank that I didn't feel I could clean and sanitize, I would modify it or even get a different one (add cleanout port, etc.)

Also helps to cut down on plastic trash (small disposable water bottles), which is not always easy to store or get rid of when underway (and I prefer to minimize it in any case).

Obviously if you can't take on potable water, then drinking out of the tank is a no-no. But I still like to have the convenience of being able to drink out of the tank, if desired.

On the other hand, I helped a friend to put a "day tank" into his RV. Reason was, water you can get to fill a large RV water tank in the southwest (for example at state parks and other campgrounds) is often VERY hard, but you can easily buy water by the gallon. So now he can fill the three gallon day tank (with separate hand pump at sink) with drinking water and then the ~50 gallon main tank with the harder water. Not that it's not potable, but just not very desirable. The day tank ended up being easier than finding places to store and set (on the counter) individual gallons.
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