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Old 08-10-2009, 09:19   #1
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Purification of Water Tanks

Hi all
we are full time liveaboards but sail quite often. We use only fresh water from our tanks (mainly for washing dishes, cleaning, showers...). the last time the tanks were thoroughly cleaned was over a year ago.
Do I need to clean them again? Can I (and with what) clean them as they are or do I need to take them out?
Thank you for any suggestions


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Old 08-10-2009, 10:11   #2
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What to Use to Clean Water Tanks ?

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Old 09-10-2009, 14:38   #3
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Having put pin holes in my aluminum hot water tank of my camper by using bleach to disinfect, I would never put bleach in my custom aluminum tanks in my sailboat.

After an extensive research, I've discovered that hydrogen peroxide is perfectly safe for aluminum tanks regardless of concentration or time of soak. I use 35% food grade H2O2 diluted to 1%. It is not cheap or safe to you (protect your eyes when diluting), but it disinfects perfectly with zero aftertaste.

Further it chemically degrades into completely harmless compounds, so it's safe for the environment when I pump out.
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Old 23-10-2009, 07:18   #4
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I have also used peroxide in my water tanks for about 6 years now. Works great plus you don't have to worry about adding to much as with bleach.
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Old 23-10-2009, 09:35   #5
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Nothing beats opening them up and cleaning them. We've had some brown (more of a copper colored really) algea that forms from time to time. You can disinfect with peroxide to kill it and stop future growth, but the garbage that's already in there won't magically disappear until you dry the tank out, and clean it with paper towls through the inspection port.

A gross job to be sure, but it's good training for the fuel tank, which is even worse.

Good luck :-)
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Old 31-10-2009, 09:11   #6
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As Posted on another Thread

I have copied my reply to another water purification thread. I strongly suggest preventative maintenance. Use bleach for any but aluminum tanks, it works and is very inexpensive. Disinfect your ENTIRE WATER SYSTEM at least annually (twice a year is not too often).
This methodology comes from very knowledgable people as I explain in the following:

"I received the following advise from Peggy Hall, also known as the "Head Mistress" and Sue Canfield, a marine surveyor. Peggy has written a very good book on boat heads and water systems (I own a copy).

To correct your water quality problems, start with a stem-to-stern inspection of the potable water system. Start with the deck fills. To prevent someone from inadvertently filling your water tanks with fuel (Believe me, it happens!), the deck fill fittings should be clearly labeled “water” or have a blue plug. With a deckplate key, unscrew each deck fill plug and look at its O-ring. If the plug isn’t water-tight (because the O-ring has deteriorated or is missing) contaminants will find their way into the tank.
Moving below, inspect the water hoses and clamps at the deck fill pipes. Look too at the condition of the hose. If the hose casing (outer surface) is discolored, cracked or tacky to touch, go get a tape and measure the hose run that needs to be replaced. Next, inspect the tank vent hoses. Vent hoses may run to external vent fittings or they may terminate inside the boat. In the latter case, make sure the end of the vent hose is higher than the tank’s deck fill. Ensure too that the exterior vents or ends of the vent hoses have screens to keep insects from taking a swim in your drinking water.
If your boat’s tanks have inspection ports, remove them and look inside. Tank cleaning to remove accumulated sediment may be in order. Next, follow the water system piping from each tank to the pressure pump. There should be a strainer (typically 50 mesh) installed in-line to prevent foreign debris from entering and damaging the pump. Clean this as needed. . From the water tanks to each fixture, note the type of piping used, its diameter and condition. Depending on your boat’s age, you may find annealed copper piping, PVC (polyvinylchloride) hose, gray PB (polybutylene) or PEX (cross-lined polyethylene) tubing or a mix of materials. Of the four materials, PVC hose typically has the shortest service life. Identify piping segments that need to be replaced due to deterioration or the use of inappropriate (non FDA-approved) materials.

Sanitizing Your Water System

Always disinfect your boat’s potable water system at the start of each boating season and whenever water taste, odor or appearance becomes a concern. Before starting, ensure that the water heater is turned off at the electrical panel. Ice-makers should be turned on to allow the feed line to be disinfected. Remove any filter cartridges as well as any aerators at faucets. Flush the entire system with potable water and then drain it completely through every faucet.
Next, fill the entire system with a chlorine solution (approx. 1/2 to 1 ounce of common household bleach per gallon of tank capacity). Run the water from each faucet or outlet until you can smell bleach at each location. Leave the system pressurized with this bleach solution in it for at least 4 hours, but not more than 24 hours. Drain the entire system again, flush it thoroughly with potable water (fill and drain at least 2 times), and discard the first two buckets of ice generated by the ice-maker (if installed). Fill the tanks with potable water, clean the sediment filter installed to protect the pressure pump, and install new water filter/purifier cartridges as appropriate. Clean and reinstall the aerators at the faucets.
Water treatment systems (filters) can be used to remove taste and odor as well as sediment, rust, algae and other microscopic solids. Point-of-use (POU) systems treat water at a single faucet. Point-of-entry (POE) systems treat water as it’s drawn from storage tanks or enters the boat via a city water inlet. I recommend both, however, be aware that some of these filters (the one when filling the boat) remove the chlorine used by the city to purify the water).

Remember, algae and contaminates can thrive in the entire water system, not just the tanks. Other than aluminum tanks, which are not approved for drinking water storage, bleach in these concentrations (and durations) will not harm the tanks or plumbing.
Good luck and hope this helps,
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Old 31-10-2009, 09:30   #7
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Great post Tom!

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Old 31-10-2009, 11:38   #8
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I use both carbon and particulate filters on all water that goes into the tank. I use hydrogen peroxide as a sterilizing agent. I don't want chlorine in the system as it may destroy my watermaker membranes.
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Old 05-11-2009, 17:08   #9
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If peroxide is used, what is the ratio per gallon of water? How long do you leave it in the system and do you flush it with a full tank of water?
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Old 07-11-2009, 04:00   #10
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This is a related question -- if you take on water of suspect quality, how do you purify it? Ideal ratio of bleach to water? Can you use peroxide for this purpose? Anyone use iodine tablets? Maybe the vodka trick would work here. . . .
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Old 07-11-2009, 07:27   #11
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Originally Posted by Cormorant View Post
Ideal ratio of bleach to water?
30ml per 1,000 liters
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Old 07-11-2009, 15:06   #12
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Thanks -- that's a tough one to measure out. Less than a teaspoon would go into my 27-gallon water tank. Good to know.
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Old 07-11-2009, 15:17   #13
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I know H2o2 can have health benifits. We have it in small doses regularly. I would not want to use bleach.

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Old 08-11-2009, 07:09   #14
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OK, I still don't know the mixture ratio for the use of Peroxide? I have used one capful of Bleach to 150 gallons of water, but I perfer not to use bleach since it can damage my water makers filter.
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Old 08-11-2009, 07:20   #15
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If you keep some R.O. water in designated jug to flush watermaker,you shouldn't have to worry about chlorine in tanks.Watermaker sends water out, not receive.Katadyn recommends making water in seperate tank,for quality control,then adding to system.

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