Steel water tank storage

[SeaSon]

I've been carrying around to too much water in my 3 tanks. I can fill up weekly, so can likely get away with just one.

2 galvanized saddle tanks are 40 years old, and one newer fiberglass in the bow. None leak, but the galvanized provide rusty water once they get low. So thinking the fiberglass tank is the one to use. Though using the starboard saddle would help trim the boat.

I read that steel water tanks should be stored full to keep oxygen away from the metal and minimize rusting, but I don't want to carry that extra 150 gallons any more.

The Question: Any thoughts on additives such as chlorine or vinegar or ... To keep algae/mold at bay and minimize further internal rusting? Other considerations?

[Lepke]

I have 1942 steel fuel tanks and 4 1970? galvanized water tanks. Same problem as you with the water. The only way I know to stop the rust and have safe water is ship tank coatings that are epoxy based. Lot of trouble to do. Sandblast, wear air supply when painting.
Fiberglass works well, but also a lot of trouble in surface prep and layup. It's usually easier to build new fiberglass or fiberglass and plywood tanks. I plan on replacing my steel water tanks with purpose made plastic tanks because some stock ones will fit the space. I have made many plywood & fiberglass fuel and water tanks in my time. I always use epoxy resin, wait until fully cured, then fill with water and a box of baking soda. That always made good tasting water and last the life of the boat if properly done. And so far I've made it to 67 drinking tank water most of the time.

[maxingout]

It's hard for me to imagine carrying too much water on board. But then we cruised with as many as five people on board, and I often wished that we had more tankage. When we go on passage, we even carry jerry cans of water for a greater safety margin.

I would not want to have a single tank just in case something went wrong with that single tank. At least two tanks would be my minimum.

I always had stainless steel water tanks, and they worked good except when in the bilge where pinhole leaks occurred.

[RaymondR]

I have been in a number of shipyards where they were internally coating steel water tanks with a white grease they called sheep grease, from this I assumed it was a lanoline based grease they were using. The grease was applied to bare steel. I would not have a clue where you would get this stuff from.


If you can get all the moisture out of the tanks and seal them airtight they should not rust, even better if you could flush them with dry nitrogen before you seal them.

[k. michael marquardt]

You cant use sheep grease for drinking water.

In commercial ships we use a slurry of pure building cement (Portland) for mild steel tanks and give the interior (all six surfaces) two or three coats, drying in between. The water keeps sweet and no fungus or growth does develop.
Plastic coating results in slime and the necessity to use additives like mentioned before.
In my boat I installed stainless steel tanks which are not coated inside and so I use chlorine to keep the fungus at bay.

[Bor the Wolf]

The traditional way to coat steel water tanks is Portland cement. It keeps the water fresh and protects the steel.

I use a 5% solution of Sodium hypochlorite (bleach) to kill any bacteria. 5% is the standard strength available in every supermarket. Do not confuse it with toilet cleaner. That stuff has thickening agents and other additives you don't want in your water tank. The stuff you want is pure bleach, thin as water (the cheapest stuff).

It is mixed 1 : 50,000 for normal use, 1 : 5.000 for shock treatment. Obviously the latter is flushed after 30 minutes.

Does it taste bad? Sure, it has a faint smell of bleach, just make your tea or coffee a bit stronger. In many parts of the world this amount of bleach (and more) is standard in tap water. So, depending on where you're from, you may not even notice.

[Rebar_Caruso]

@ max...

always had stainless steel water tanks, and they worked good except when in the bilge where pinhole leaks occurred.[/QUOTE]

Gotta ask.... what caused the pinhle leaks?

[maxingout]

Originally Posted by Rebar_Caruso

@ max...

always had stainless steel water tanks, and they worked good except when in the bilge where pinhole leaks occurred.

Gotta ask.... what caused the pinhle leaks?[/QUOTE]

The stainless steel tank was under the floor boards of my Westsail 32. Bilge water splashed up on the bottom of the tank over twenty years and lots of pinhole leaks developed. I did not realize the leak was present until I heard the bilge pump go off after sailing into St. Thomas USVI.

I pulled the tank, and I encased the entire tank in Fiberglass which permanently solved the problem.