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Old 01-14-2013, 07:33 PM   #21
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Regarding crevice corrosion in stainless water tanks I have wondered why the tanks in our boat have not yet succumbed to this as they are as old as the boat (1973). The only thing I can think of is that the water turnover int the tanks has always been fairly high. We go through a lot of water on our boat as we use it all year even when we don't take it out and perhaps the previous owners did the same.

I would agree that the tank construction described by Tony Fleming is superior as long as the tank material does not impart a taste into the water.
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Old 01-14-2013, 07:46 PM   #22
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Regarding crevice corrosion in stainless water tanks I have wondered why the tanks in our boat have not yet succumbed to this as they are as old as the boat (1973). The only thing I can think of is that the water turnover int the tanks has always been fairly high. We go through a lot of water on our boat as we use it all year even when we don't take it out and perhaps the previous owners did the same.

I would agree that the tank construction described by Tony Fleming is superior as long as the tank material does not impart a taste into the water.
You're probably not adding any chlorine to your tanks filled with Bellingham city water, either. (But there may be a small amount in the city water supply?) Tony seems to feel that the presence of chlorine is a contributing or accelerating factor.
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Old 01-14-2013, 08:16 PM   #23
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I appreciate all of the comments but I would really like to hear from folks that actually have aluminum tanks. Chuck
A number of years ago...I replaced a cracked poly tank with an aluminum tank for water.... Only after the fellow finished and I paid for the tank... I was told I could have had a stainless steel tank for about $50 more!!

Maybe I occasionally suffer from CRS because the tank was aluminum, but I doubt it.... At any rate...i spent more than $50 more to prep the tank to install it in the boat....

Given my druthers.... I would go with a poly or stainless steel tank.

Or...custom build one with FRP...
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Old 01-14-2013, 08:51 PM   #24
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You're probably not adding any chlorine to your tanks filled with Bellingham city water, either. (But there may be a small amount in the city water supply?) Tony seems to feel that the presence of chlorine is a contributing or accelerating factor.
You're correct--- we don't add anything to the water in the fresh water tanks. And I have no idea how Bellingham treats its water but when I've drunk from drinking fountains and such up there, there does not seem to be any noticeable chlorine taste.
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Old 01-15-2013, 12:45 AM   #25
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If you decide to use a plastic tank, and I think you should, these are the guys you should buy it from: http://www.ronco-plastics.com/newRonco/index.php
They make heavy walled roto molded tanks in about 500 different sizes and shapes.
My Ronco water and holding tank are all over 20 years old now and I'm very happy with them.
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Old 01-15-2013, 03:34 AM   #26
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I must agree with everybody else.
SS is the only way to go for small boat water tanks.
I had 2 x 1000 lt ss tanks in Tidahapah and after 15 years cut them open to decrease their size( I was fitting a water maker) in all this time there was barely any sludge in the tank bottoms , a quick wipe out new ends formed and welded in. Good as new. That was 4 years ago. Water is always perfect and I just run a carbon filter on the line to the galley sink.
No bottled water on this vessel as it is one of the great cons performed on the world wide public.
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Old 01-15-2013, 07:30 AM   #27
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I must agree with everybody else.
SS is the only way to go for small boat water tanks........
"Everybody else" did not recommend stainless steel tanks. Many recommended polyethylene. They are less expensive than SS, weigh less, and you can see the water level through the tank walls and/or install an external level sensor system.
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Old 01-15-2013, 08:27 AM   #28
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Well I'll be fitting a 500ltr ally fuel tank in the aft and a 500ltr fresh water tank in the bow of my boat and will be installing it as per the methods in the bottom link.

The tank walls are 10mm thick and i have every confidence that they will work just fine without the risk of Crevice Corrosion. I'm not to concerned as to the so called "medical" disadvantages of aluminium tanks either

A correctly mounted aluminum marine fuel tank of high quality material, and under ideal conditions should outlast the boat. Some say they last 25-30 years, but I think they may go even longer as I've seen them past that mark and still in good shape. I've also seen some in the 15 year range that looked to be 50 years old due to crevice corrosion. Aluminium marine fuel tanks often have baffles in them to stabilise the fuel from swashing around excessively. Aluminum tanks are custom made, so getting one to match your boats design is a snap. A custom marine aluminium fuel tank can take advantage of extra space and allow for more fuel capacity. Aluminum fuel tanks are stronger and resist punctures better than plastic. Aluminium tends to dent and withstands more punishment. On a rebuttal side, I really don't see how a properly secured tank would be at risk, but during install this could be of concern.

One of the biggest issues in aluminium marine tanks are from builders foaming in the tanks. Aluminium tanks do not like moisture over prolonged periods, and the foam against the tank enables major corrosion to occur. The constant jarring of the boat eventually creates a seem between the tank and foam, which allows any moisture, whether from deck water running in or from simple condensation to do its damage. A properly mounted aluminium will have good airflow around all surface areas, thus allowing it to dry. Studies show that aluminium marine tanks are structurally sound for 10 years and in most cases longer

I have always been a fan of aluminum, as it's stronger, and as far as metal goes, I feel it is the best alloy for marine use hands down.

In relation to the medical factors, If I remember reading articles on this subject, (no pun intended) i think they may have been referring to users of aluminium saucepans, where the edges of the pan were constantly being scraped with steel spoons and the like - adding aluminium particles to the food. I'd read that the team that cut up and analysed the brains of old timers disease victims made a basic mistake by using aluminium contaminated instruments - but then again you can't believe everything that you read.

I believe the aluminium paranoia is unfounded. You cannot avoid it. Food processing, tanks, medicines, kitchenware, baking powder, flour, beer, cheese and salt even. The dust we breath has more aluminium in it than anything else. It's just silly. The medical problems are related to aluminum getting into the body thru dialysis or IV meds using impure water...not likely to happen on a boat. The paranoia started in the 1970's and never went away. To avoid aluminum is simple, just don't drink, eat or breathe.

I've had an 40 litre aliminium belly tank on my troopie for 10 years never had a problem - flush at least once a year and I'm fine .... Twitch ..... Twitch ..... Twitch ..... hahahahahahahahahahahaha

I also think with the discussion in the thread "Natures Head" of people pissing and shitting in the ocean, y'all have more diseases and contaminates to worry about than the so called "contaminates" from an ally tanks.

Roll the dice and take your chances. Do what you can afford and you'll be fine.



http://marinesurvey.com/yacht/fueltank.htm

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Old 01-15-2013, 09:29 AM   #29
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Epoxy composite is a possibility for custom tanks (water or fuel)...based on what aluminum fabricators are getting in the NJ area...I had even contemplated making my own fuel tanks to keep costs down.
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Old 01-15-2013, 09:45 AM   #30
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Epoxy composite is a possibility for custom tanks (water or fuel)...based on what aluminum fabricators are getting in the NJ area...I had even contemplated making my own fuel tanks to keep costs down.
There is a good discussion on building tanks using epoxy in the book, "The Gougeon Brothers on Boat Construction", 5th Ed. They do not recommend West System for potable water or gasoline tanks. Diesel, sewage and gray water have held up well using West System epoxy though.
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Old 01-15-2013, 12:38 PM   #31
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There is a good discussion on building tanks using epoxy in the book, "The Gougeon Brothers on Boat Construction", 5th Ed. They do not recommend West System for potable water or gasoline tanks. Diesel, sewage and gray water have held up well using West System epoxy though.
While they are experts...they are not the final say....there have been integral water tanks in glass boats for years...epoxy is used to line many different types of tanks....

Don't know if it's their epoxy that shouldn't be used...there are lot's of formulations and the right ones are definitely needed for ethanol gasoline and biodiesel...but for water I don't see their logig is complete boats are built from the stuff...maybe it's just not economical at their epoxy prices...
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Old 01-15-2013, 12:45 PM   #32
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Right from their site....

Builders have successfully constructed tanks for potable water, sewage, gray water, ballast and diesel fuel tanks and a limited number of gasoline tanks using WEST SYSTEMŽ epoxy since the early 1970's. The regulatory environment has evolved within the last thirty years and has placed safety restrictions on various aspects of tank building, specifically potable water and gasoline.


Regulations have made all of boat building more difficult and costly. If the correct epoxy is used...I'm pretty sure under normal temps and usage...it is more inert than the metal and equal to or more so than the polyethylene tanks.
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Old 01-15-2013, 05:35 PM   #33
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It would take a really good reason to steer me away from a stock polyethylene water tank or tanks. No corrosion, no taste or health issues, and I suspect they are the least costly option.

For those with special needs or who just like to be different from everyone else, consider a bladder tank. Essentially a beavy duty rubber balloon that gets bigger when you add water and smaller as you use the water.
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Old 01-15-2013, 09:25 PM   #34
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Once again I appreciate everyone's input. My research is showing that aluminum is perfectly acceptable for water tanks with the caution that care needs to be taken to make sure no chlorine gets in the tank. That will mean special filters for filling the tank IF we go that way. I really want some feedback from owners that have aluminum tanks and their experience. I'm not looking for recommendations for what material to use. Thanks, Chuck
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Old 01-15-2013, 10:27 PM   #35
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I really want some feedback from owners that have aluminum tanks and their experience. I'm not looking for recommendations for what material to use. Thanks, Chuck
From some of the posts I've seen (including mine), you have have been given exactly that. Albeit some posts from a second source.

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Old 01-15-2013, 10:46 PM   #36
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Once again I appreciate everyone's input.
as I said.
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Old 01-15-2013, 10:57 PM   #37
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I really want some feedback from owners that have aluminum tanks and their experience.
My guess is that the lack of response is because, despite the fact this forum represents but a tiny fraction of the boat owners out there, there are precious few boats with aluminum water tanks for the reasons that have been stated.

I suspect that if aluminum was truly a good material to build water tanks out of it would be the material of choice by many if not most boat manufacturers. It's cheap, it's light, and it's relatively easy to work with. Why make stainless tanks when aluminum is so much cheaper, lighter, and possibly easier to work with?

There must be a reason why you almost never see aluminum fresh water tanks, and if it's not high cost or difficulty of manufacturing or high weight, what it it?

Perhaps making a case for aluminum water tanks is like designing and building a house using the formula 2+2=5? There's a good reason you don't use it? I dunno..........
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Old 01-15-2013, 11:51 PM   #38
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Greetings,
Aluminum water tanks......
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Old 01-16-2013, 12:19 AM   #39
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SS tanks come back in weight due to the small thickness of the material used (compared to al) and the ease of welding a complete non porous weld plus the inherent strength.

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Old 01-16-2013, 12:22 AM   #40
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SS tanks come back in weight due to the small thickness of the material used (compared to al) and the ease of welding a complete non porous weld plus the inherent strength.

Benn
I did not realize that for a given application like a tank SS is lighter than aluminum. Thanks for the correction.
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