Cleaning S/S water tanks

[Nicholson58]

We cleaned our tanks using a power washer with 90-Ell added to the nozzle. I could snake the wand over the baffles to get most of the red organic loose. Brown algae? Good advice on filters & shock from the others. If you don't have access, consider adding inspection ports.

[sailcrazy]

Thanks very much for all the replies, and I agree that putting additional inspection holes in ea tank would be a big help. but how do you cut a new hole in S/S without dropping alot of filings and crap into the tank? What tool did you use to cut the new access hole into the S/S top? I guess once the hole is cut you could put you hand under when you drill the bolt holes with a cobalt drill and catch the filings and metal bits from below.

[Terra Nova]

Once the hole is cut it is easy to clean up the filings. Which would you rather have, growth in your tank that can make you ill, or some inert filings to vacuum out?

[sailcrazy]

I agree.....but how do you cut the hole in S/S? We carry a sabre saw onboard, but none of the steel-cutting saws will touch the S/S top of the tank. Any ideas on how-or what to use-to cut the initial hole?

[Terra Nova]

A saber saw will work using the correct bi-metal blade.

[Cruisingscotts]

Ro water is slightly acidic, becuase of this it will tend to leach any ferrous material it comes in contact with, 304SS welds that were not passivated, a steal pipe fitting or plug somewhere, a steel bolt somewhere coming in contact with it. The result is what you would expect, rust and slightly orange colored water. Finding the source is important, cabon filters will clean it out, it will also remove any chlorine you have dosed in the event you want to go high, 2.5 to 3ppm is in the don't poop your pants range, 4ppm is sure to give someone GI issues. . Some algeas will also give a orangish color but tend to have a very strong odor to accompany it.

Note for cutting SS, it does not like heat at all. It will harden very quick once heated. As mentioned above a good metal cutting saber saw blade or hole saw etc. Go slow and use lots of coolant. In the event you don't have access to cutting fluid, motor oil will work. Drill a large hole for starting, bigger than the blade. Don't force the saw and if it has the option don't use any blade ocilation, set it at zero. Make a gradual continuous radius to avoid binding the blade. Use lots of blades, if you think it is getting dull change it. And once again go slow let the saw cut the hole. It will sound like nothing you have ever encounter so probably anchor very far away from friends.

[Terra Nova]

Don't contaminate your water tank with cutting/motor oil.

[Cruisingscotts]

Originally Posted by Terra Nova

Don't contaminate your water tank with cutting/motor oil.

If you cut a hole in a potable water tank you are going to contaminate it....

Cutting the hole out with two people, one cutting and one using a shopvac by the blade will eliminate most of the metal going anywhere as the blade cuts on the up stroke. If you go very slow and use high quality blades you can probably cut it dry with a saber saw or variable speed jig saw, just ensure it doesn't get hot. Once the access hole is cut, you can put something in the tank bottom to catch filings etc and minimize the nessesary cleanup from drilling holes to mount a access port. Drilling holes in SS without lubrication is not advisable, with a new high speed steal or cobalt bit you can probably drill one or two holes through 14gauge ss which is what your tanks are most likely made of, after that the bit will be dull enough to heat the metal and give you lots of headaches. A very small amount of lubrication is all thats needed, think couple drops. Always drill a small pilot hole first, 3.5mm, 4mm or standard equivilant is a good size. Upsize the hole to what you need after. Even pressure when drilling then slightly speed up the drill right before finishing drilling the hole. It will leave a very sharp bur on the underside of the tank. A right angle drill with a counter sink bit can be used to de-bur. De-bur both sides of the hole both top and bottom. Small filings or burs can get into fastner SS fastner threads and cause gauling between the nut and bolt/machine screw. A small amount of dish soap and rag will remove any oil residue.

[thinwater]

What Cruisingscotts said. Probably iron.

[Cruisingscotts]

It goes without saying use proper PPE, gloves, hearing protection and safety glasses. Never try to remove chip stock or drill filings with bare hands. When working with SS always remember the part that makes it Stainless is chromium. This is not usually a issue cold cutting or drilling, but definately something to consider using abrasives cuttoff wheels, welding or anything that brings the metal temperature to red hot. It falls into the "not sure yet" catagory of health and safety of what the long term exposure effects are.

[Cheechako]

It could be organic or could be rust. Try the shock first.
Look inside the tanks of one you already have an access to. If slimy red it's organic. Sometimes the top of the tank is the worst as it often not in constant contact with the water.
Not sure the time to create an access into the one tank is worth it. Clean a tank that you have access to and see how long it lasts... might not be very long anyway. maybe a time schedule for shock treatments is best.

[dlymn]

All good advice about hole cutting so far. I notice that if any grinding waste gets on the gelcoat it leaves rust marks and I would guess that would also be true of swarf left inside the water tank. Remember that you're cutting an access hole and so you should be able to do a good job of cleaning all of that up. Do you know where the baffles are, because you don't want to make your cut over them. When some people cut holes in diesel tanks, they don't get too worried about swarf because they know that the primary filter will pick it up. I have had little success using snips to cut stainless but that might be saying something about me and my snips.

[Cheechako]

I have a pair of Boss Sheet Metal nibblers.... electric. It punches out little plug rather than cutting and creating dust etc. Supposedly good for up to .100"

[Ribbit]

Seriously, AVOID putting chlorine in SS tanks (or anything SS). SS reacts really badly to it, and I had to get some information about it urgently to an architect who had specced structural SS plates, fixtures, fittings, and nails, for a roof over a swimming pool at a holiday park locally to me. Luckily I arrived on site just as they were starting to use them, a pure fluke.

The chlorine from the pool would have rotted out all the SS in no time (I had nightmares about that very large and heavy roof collapsing while there were families using the pool).

I faxed so much information on it to the architect, his fax paper ran out half way and I had to send it all again the following morning.

We substituted copper and other satisfactory replacements (with one architect breathing a massive sigh of relief, along with the owner).

eta: A quick insight from here should be enough (but there's way more at other places):

http://www.estainlesssteel.com/corrosion.shtml

"Types of Stainless Corrosion

According to the DOD Technical Bulletin Corrosion Detection and Prevention there are 8 separate types of corrosion, with only a few having a major impact on stainless steel. Please be advised the descriptions below are extremely brief and written in laymen terms. Before acting on any particular application, qualified advice particular to such application should be obtained.

1. Uniform Attack - also known as general corrosion, this type of corrosion occurs when there is an overall breakdown of the passive film. The entire surface of the metal will show a uniform sponge like appearance. Halogens penetrate the passive film of stainless and allow corrosion to occur. These halogens are easily recognizable, because they end with "-ine". Fluorine, chlorine, bromine, iodine and astatine are some of the most active."

So don't add iodine either.

[tommyboy-afloat]

I have worked with domestic water making systems and have found on occasion that if you are unlucky enough to get iron bacteria into your system then it can be a real problem. I am not sure if the same situation can occur in salt water but it does work in salty ground water.
Once in the system it can stay forever unless treated. I found info on it by typing iron bacteria into the search engine.
It may be relevant or irrelevant.

Thanks for all the info on cleaning or sanitizing a tank