Free water

Kermit

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Jul 31, 2010
5,657
AquaCat 12.5 17342 Wateree Lake, SC
I would think rainwater would be pretty dang pure. Maybe I’m wrong but shouldn’t it be?
 
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Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
I think the rain water might be pure, as it is kind of distilled, but it is the air that it falls through that make it dirty.
 
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jwing

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Jun 5, 2014
503
ODay Mariner Guntersville
Rainwater can contain contaminants. Sometimes the water vapor condenses on airborne particles. Rain can also collect contaminants on its way through polluted air, this is the principal that makes power plant exhaust scrubbers effective. You've heard of acid rain?

In Utah, storms that approach from the west kick up salt particles from the Great Salt Lake Desert. Then they pick up water vapor from the Great Salt Lake. When they encounter the Wasatch Mountains, orographic lifting causes the water vapor to condense on the tiny salt particles. The salt acts as a desiccant, causing the snow to be very dry, resulting in the powder skiing for which the Wasatch Range is famous.

I took off on that non-sailing tangent to illustrate that contaminated rain is generally caused by a local phenomenon. It is not widespread. Be aware of the world around you.
 
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capta

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Jun 4, 2009
4,766
Pearson 530 Admiralty Bay, Bequia SVG
Did you see the grey teak toe rail? That's dirt and salt that makes it grey. Imagine the dirt in the toe rail to deck joint. If one wants to collect rain water to drink, one must have a dedicated system that is perfectly clean. A tarp that is stowed and only unfolded for collecting drinking water. An area of the deck or cabin top that can be washed before the rain water is fed into the tanks.
Cisterns are a whole different kettle of fish. The water sits in there and any impurities can settle out and the pick up tube is above this settling section, like a fuel tank. Then it is bleached and filtered. Boat tanks are almost perpetually moving, disturbing any settling process.
Anytime one is anchored anywhere near shore, especially on the sheltered leeward side of an island, there is going to be dirt and contamination on any surface except a dedicated tarp or washed surface. If you have a dodger, this can be seen quite easily. After a good rain, wash the Isinglass and see how much dirt is left.
We often get dust settling on the boat that has come all the way from the Sahara Desert. That dust is so fine it gets into the cloth of the dodger, the bimini, wood grain and around stanchion bases and jib car tracks. and yet it is unseen as it washes into your tanks.
Unfortunately, once a baffled tank gets contaminated, there is little one can do but remove it, cut some access holes in each section and wash it with steam, before replacing it, not a fun project.
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Unscented bleach (sodium hypochlorite) is an easy to find and an effective tool for the treatment of potable water in storage. You want to maintain between 1 and 2 ppm in the water.

Here is a dosage calculator from Public Health Ontario.

Just filling your tanks, you should shock the tank. Recommend 10 ppm.
Here is is Oregon Health Agency calculator for shocking a tank.

Don't think more is better, this stuff is a powerful oxidizer and can do a number on your tank, plumbing and fittings.
 
Jan 11, 2014
11,321
Sabre 362 113 Fair Haven, NY
Last year we stayed in a camp in near Volcanoes National Park in Hawaii. The water was collected from the roof, and feed into a cistern and then pumped back to the house through copper pipes.

The shower floor had a nice turquoise color, just about the shade of copper sulfate. Apparently the water filter didn't need to filter out the sulfuric acid in the rain as it reacted with the pipes.
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
For safety sake, I always add a carefully measured 75 ml of water treatment to my water at the tap. It goes by the brand names "Bombay" or "Mount Gay". It may not stop bacteria, but it can't hurt.
Years ago my Pappy was taking a boat south with Ma and another couple. Each day the crew became increasing ill, all except the old man. None of them responded to their Dramamine meds. Upon further investigation Pap determined that unlike himself, his crew was mixing drinks each evening with ice they were making in the galley freezer...from the tap. He was drinking his Black Label beer from a can. Liked to tell the story about how he converted them all to beer drinkers!
 
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
Speaking as a civil engineer, rain water is very soft (not a lot of minerals in it so it makes soap bubbles really well) and makes cleaning tasks easier. You do get "dirt" and biologicals from the air though. Course those biologicals are the same ones you breath in all the time and the dirt will settle out in the tank!! Standard practice is to "waist" the first few minutes of rain to clean the collecting surface of bird poo and the like. A simple carbon filter is sufficient to render "after waist" water officially potable. You will notice (rather not notice) the taste of rain water and how much easier it is to clean with it. soap goes a lot further with soft water.
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
A simple carbon filter is sufficient to render "after waist" water officially potable.
Not sure what you define as a "simple carbon filter", but most household and boat-installed filters (including that Brita thing) are poor filters for the bugs and cysts. I have a carbon-block camp filter that works but the granular types are designed to filter volatiles and herbicides. You have to pre-treat to make it microbiologically safe.
 
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Oct 2, 2008
3,807
Pearson/ 530 Strafford, NH
Well I thought Texans drank their water from horses hoof prints. After three days of steady rain we were pretty sure the deck was clean. We use this water for washing dishes and the head. All drinking water is bottled which is probably worse. With T-storms all afternoon, we added about 50 gallons which should be enough for our stay here in the Bahamas. Oh we do have a charcoal filter on the system and a Seagull in the galley.

All U Get
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
A Seagull filter is a carbon block filter and is capable of filtering microorganisms and viruses out of the water. It is a superior filter if you have the reduced flow model.
 
Mar 1, 2012
2,182
1961 Rhodes Meridian 25 Texas coast
Well I thought Texans drank their water from horses hoof prints. After three days of steady rain we were pretty sure the deck was clean. We use this water for washing dishes and the head. All drinking water is bottled which is probably worse. With T-storms all afternoon, we added about 50 gallons which should be enough for our stay here in the Bahamas. Oh we do have a charcoal filter on the system and a Seagull in the galley.

All U Get
every place I was at in the Bahamas had RO water available at quite reasonable costs
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
Don't think more is better, this stuff is a powerful oxidizer and can do a number on your tank, plumbing and fittings.
I like this water treatment Chemical and the final product are Oxygen and Water, Not Chlorine. Chlorine Bleach is damaging to many rubbers and wood.

https://www.amazon.com/Members-Mark-Hydrogen-Peroxide-fl/dp/B01LNWSL7W/ref=sr_1_3_a_it?ie=UTF8&qid=1515765452&sr=8-3&keywords=hydrogen+peroxide

Both Peroxide and bleach are great for treating Stings from Jellyfish too. Hold a soaked paper towel on the wound and Pain stops within minutes. Both oxidize the venom.;)
Jim....
 
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pateco

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Aug 12, 2014
2,207
Hunter 31 (1983) Pompano Beach FL
I like this water treatment Chemical and the final product are Oxygen and Water, Not Chlorine. Chlorine Bleach is damaging to many rubbers and wood.

https://www.amazon.com/Members-Mark-Hydrogen-Peroxide-fl/dp/B01LNWSL7W/ref=sr_1_3_a_it?ie=UTF8&qid=1515765452&sr=8-3&keywords=hydrogen+peroxide

Both Peroxide and bleach are great for treating Stings from Jellyfish too. Hold a soaked paper towel on the wound and Pain stops within minutes. Both oxidize the venom.;)
Jim....

I use this as a no rinse sanitizer in my brewing equipment.

Iodophor Sanitizer

Was thinking of running some through my whole system the next time the tank is empty.

Much better than bleach. No flavor or smell, you do not need to rinse once sanitizing is complete, and you can get it online or at most brewing supply stores.
 
Jan 11, 2014
11,321
Sabre 362 113 Fair Haven, NY
I like this water treatment Chemical and the final product are Oxygen and Water, Not Chlorine. Chlorine Bleach is damaging to many rubbers and wood.

https://www.amazon.com/Members-Mark-Hydrogen-Peroxide-fl/dp/B01LNWSL7W/ref=sr_1_3_a_it?ie=UTF8&qid=1515765452&sr=8-3&keywords=hydrogen+peroxide

Both Peroxide and bleach are great for treating Stings from Jellyfish too. Hold a soaked paper towel on the wound and Pain stops within minutes. Both oxidize the venom.;)
Jim....
Hydrogen Peroxide is a decent antibacterial agent, I wonder about its effectiveness on mold, mildew, and those sort of flora and fauna. Also, what level of concentration would be appropriate? The product you listed is 3% H2O2, if that is the lowest concentration to be effective, then it would take a lot to sanitize a 120 gallon water system. Also, H2O2 is unstable, it naturally separates in to water and oxygen fairly quickly, so be sure to use a fresh supply.

I use this as a no rinse sanitizer in my brewing equipment.

Iodophor Sanitizer

Was thinking of running some through my whole system the next time the tank is empty.

Much better than bleach. No flavor or smell, you do not need to rinse once sanitizing is complete, and you can get it online or at most brewing supply stores.
This is interesting. According to the SDS it is iodine and hydoriodic acid. Basically the stuff in the water purification tablets we used to use in Boy Scouts. Again the issue is what concentration is necessary to clean a large water system on a boat, it may work well, but be inordinately expensive.

Where's our resident chemical engineer?
 
Jul 7, 2004
8,402
Hunter 30T Cheney, KS
This discussion is pushing me to go forward with an inline filter in my water system. I already filter what comes in from the dock.