Reply
 
Thread Tools Search this Thread Display Modes
 
Old 10-22-2020, 09:35 AM   #1
Veteran Member
 
stiggy's Avatar
 
City: Seattle
Vessel Name: Bailey
Vessel Model: 46' Grand Banks Motor Yacht
Join Date: Apr 2019
Posts: 46
Fresh water tank crud

Starting a refit of our tank monitoring and the first tank Iím working on is our aft fresh water tank. After I drained it I figured Iíd have a look inside, kind of a good idea, kind of a bad idea! The tanks are aluminum. Am I looking at calcium deposits or something else?
So hereís some clips from the horror show:
Attached Thumbnails
9300DAA5-B643-402D-97E1-EFDDE0FEB66C.jpg   2C7851B6-8504-47A0-99B2-0FC7628BBBA7.jpeg  
__________________
Advertisement

stiggy is online now   Reply With Quote
Old 10-22-2020, 10:32 AM   #2
Guru
 
kthoennes's Avatar
 
City: Sioux Falls, South Dakota
Vessel Name: Xanadu
Vessel Model: Mainship 37 Motor Yacht
Join Date: Oct 2013
Posts: 1,254
Right there, that's why we never drink the tank water. I don't care how clean it smells and tastes or how clean I think the tanks are or whether there's an inline filter. Even if those deposits are purely mineral, eew.
__________________

kthoennes is offline   Reply With Quote
Old 10-22-2020, 11:53 AM   #3
Senior Member
 
jungpeter's Avatar
 
City: Everett
Vessel Name: LIBERTY
Vessel Model: TOLLY 48
Join Date: Mar 2013
Posts: 277
Hi Stiggy,

While no chemist, my investigations into exactly your issues with my aluminum water tanks has lead me to my personal opinion: aluminum fresh water tanks are absolutely wrong for pleasure boat use. Again, while no chemist, it is my belief that all marine-grade alloys commonly used for freshwater tanks react negatively to the presence of generic chlorine in most city water systems commonly used to fill our tanks when pierside. The presence of chlorine negatively reacts with the alloying elements in the tank walls (manganese, magnesium, chromium, etc.) to leach out what I call "crusticles" (see attached picture from one of my tanks). Are they aluminum oxide? Aluminum chloride? Only a mass spectrograph will tell for sure.

While I disagree that these crusticles pose a significant health risk, they DO form corrosion pockets under each and every one of them. These pits can, and absolutely WILL cause aluminum water tanks to eventually fail. My best, but educated guess is that aluminum water tanks aboard pleasure boats have a 20-year useful life. Beyond that, they're on borrowed time.

Unfortunately, I know of no "fix" for the situation, as few water tanks in production boats are designed for routine inspection, which MAY allow routine cleaning, and possible mitigation of the crusticles before they fail the tank. "Mouse milk" (liquid sealers, for instance) have limited viability, primarily because of the inability to access 100% of the tank's interior on a routine basis.

In my opinion, the only option for tanks in your condition is to remove them, and replace them with either custom made stainless (316-L) tanks, or plastic. In my case, I've been unable to locate plastic tanks with sufficient volume or correct form factor to allow me to use plastic tanks for my replacements, and have used custom welded 316-L tanks as my solution to the exact situation you find yourself in. And yes, I've looked through the Ronco catalog (huge, but not huge enough for my purpose!) until my teeth hurt to no avail. And yes, I've investigated custom welded plastic tanks as well. Believe it or not, custom stainless tanks are, in fact, cheaper and WAY more available, at least here in the Pacific Northwest.

Regards,

Pete
Attached Thumbnails
Picture 166.jpg  
jungpeter is offline   Reply With Quote
Old 10-22-2020, 12:37 PM   #4
Veteran Member
 
stiggy's Avatar
 
City: Seattle
Vessel Name: Bailey
Vessel Model: 46' Grand Banks Motor Yacht
Join Date: Apr 2019
Posts: 46
Quote:
Originally Posted by jungpeter View Post
Hi Stiggy,

While no chemist, my investigations into exactly your issues with my aluminum water tanks has lead me to my personal opinion: aluminum fresh water tanks are absolutely wrong for pleasure boat use. Again, while no chemist, it is my belief that all marine-grade alloys commonly used for freshwater tanks react negatively to the presence of generic chlorine in most city water systems commonly used to fill our tanks when pierside. The presence of chlorine negatively reacts with the alloying elements in the tank walls (manganese, magnesium, chromium, etc.) to leach out what I call "crusticles" (see attached picture from one of my tanks). Are they aluminum oxide? Aluminum chloride? Only a mass spectrograph will tell for sure.

While I disagree that these crusticles pose a significant health risk, they DO form corrosion pockets under each and every one of them. These pits can, and absolutely WILL cause aluminum water tanks to eventually fail. My best, but educated guess is that aluminum water tanks aboard pleasure boats have a 20-year useful life. Beyond that, they're on borrowed time.

Unfortunately, I know of no "fix" for the situation, as few water tanks in production boats are designed for routine inspection, which MAY allow routine cleaning, and possible mitigation of the crusticles before they fail the tank. "Mouse milk" (liquid sealers, for instance) have limited viability, primarily because of the inability to access 100% of the tank's interior on a routine basis.

In my opinion, the only option for tanks in your condition is to remove them, and replace them with either custom made stainless (316-L) tanks, or plastic. In my case, I've been unable to locate plastic tanks with sufficient volume or correct form factor to allow me to use plastic tanks for my replacements, and have used custom welded 316-L tanks as my solution to the exact situation you find yourself in. And yes, I've looked through the Ronco catalog (huge, but not huge enough for my purpose!) until my teeth hurt to no avail. And yes, I've investigated custom welded plastic tanks as well. Believe it or not, custom stainless tanks are, in fact, cheaper and WAY more available, at least here in the Pacific Northwest.

Regards,

Pete
Pete,
Thanks for the reply. Our aft tank is 145 gals and under our generator. I guess I'll need to start looking at replacement options in the near future.
Do you mind sharing some of the places you contacted up here in your search for replacement?
stiggy is online now   Reply With Quote
Old 10-22-2020, 01:20 PM   #5
Veteran Member
 
City: Ft.Lauderdale
Vessel Name: Sandpiper
Vessel Model: 1976 Marine Trader D/C
Join Date: Mar 2015
Posts: 38
When replacing my water tanks I discovered a full size rubber mallet that had been left inside during fabrication. Forgotten during lunch break I suppose.
Trawler Sandpiper is offline   Reply With Quote
Old 10-22-2020, 01:38 PM   #6
Senior Member
 
jungpeter's Avatar
 
City: Everett
Vessel Name: LIBERTY
Vessel Model: TOLLY 48
Join Date: Mar 2013
Posts: 277
Hi Stiggy,

Premier tank manufacturer in the PNW is:

Coastline Equipment, Inc.
Bellingham, WA.
https://coastlinemarinetanks.com/

Ask for David in the Tank Shop.

Regards,

Pete
jungpeter is offline   Reply With Quote
Old 10-22-2020, 03:12 PM   #7
Member
 
City: Boulder
Vessel Name: Skipper
Vessel Model: Everglades DC230
Join Date: Oct 2020
Posts: 12
That looks like biomass to me. I work in the corrosion industry and aluminum is a great choice for many things, unless the pH of the water is high. Aluminum is resistant to corrosion if the pH is slightly acidic. Many municipal waters are alkaline (pH>7.0, and many times, >8.0). That's not normally aggressive water, but not ideal for aluminum.

I'd be curious if you ever add chlorine to this tank or if the water you fill with is chlorinated. If the water sits stagnant more than a few days, the chlorine will dissipate and not be there to kill "bugs" (bacteria, etc.). I normally add a small amount of chlorine to storage tanks at each filling. About 1/4 ounce bleach per 100 gallons of water.

But, 316L is the best, by far, IMO. The only common thing that attacks stainless is chlorides (not the same as chlorine, by the way) and only then above 200 ppm or so.

If you can upload or send me a higher-resolution picture, maybe we can tell, for sure, what it is.
H2O_Doc is offline   Reply With Quote
Old 10-22-2020, 06:53 PM   #8
Veteran Member
 
stiggy's Avatar
 
City: Seattle
Vessel Name: Bailey
Vessel Model: 46' Grand Banks Motor Yacht
Join Date: Apr 2019
Posts: 46
Quote:
Originally Posted by H2O_Doc View Post
That looks like biomass to me. I work in the corrosion industry and aluminum is a great choice for many things, unless the pH of the water is high. Aluminum is resistant to corrosion if the pH is slightly acidic. Many municipal waters are alkaline (pH>7.0, and many times, >8.0). That's not normally aggressive water, but not ideal for aluminum.

I'd be curious if you ever add chlorine to this tank or if the water you fill with is chlorinated. If the water sits stagnant more than a few days, the chlorine will dissipate and not be there to kill "bugs" (bacteria, etc.). I normally add a small amount of chlorine to storage tanks at each filling. About 1/4 ounce bleach per 100 gallons of water.

But, 316L is the best, by far, IMO. The only common thing that attacks stainless is chlorides (not the same as chlorine, by the way) and only then above 200 ppm or so.

If you can upload or send me a higher-resolution picture, maybe we can tell, for sure, what it is.
I personally never add any but weíve only had this for 10 months out of 25 years. I do not pre-filter into the tanks as Iíve been told to let the city water keep things clean.

Iíll try and get another picture next time itís emptied. Do you have any recommendations on maybe reversing some of this?

If it isnít blatantly obvious, I have no idea what Iím doing hahaha.
stiggy is online now   Reply With Quote
Old 10-22-2020, 07:02 PM   #9
Guru
 
O C Diver's Avatar
 
City: Fort Myers, FL... Summers in Crisfield, MD
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 9,566
I'm of no help on your tank situation, but that first picture looks like you are growing oysters in the tank.

Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
O C Diver is offline   Reply With Quote
Old 10-22-2020, 07:03 PM   #10
Guru
 
OldDan1943's Avatar
 
City: Aventura FL
Vessel Name: Kinja
Vessel Model: American Tug 34 #116
Join Date: Oct 2017
Posts: 6,381
If you cannot find an AL or stainless tank replacement, you can get one or two "plastic" tanks to fill the space with a cross over line to allow for automatic leveling.
You may lose a bit of volume but nothing significant.

On my AT has a plastic holding tank and AL water tank.
__________________
The meek will inherit the earth but, the brave will inherit the seas.
OldDan1943 is offline   Reply With Quote
Old 10-22-2020, 07:14 PM   #11
Member
 
City: Boulder
Vessel Name: Skipper
Vessel Model: Everglades DC230
Join Date: Oct 2020
Posts: 12
Quote:
Originally Posted by stiggy View Post
I personally never add any but weíve only had this for 10 months out of 25 years. I do not pre-filter into the tanks as Iíve been told to let the city water keep things clean.

Iíll try and get another picture next time itís emptied. Do you have any recommendations on maybe reversing some of this?

If it isnít blatantly obvious, I have no idea what Iím doing hahaha.
I'd need to do a little more research to be 100% sure, but I'd think about using peracetic acid (PAA) diluted in water. Breweries use this to clean tanks. It has the advantage of being an acid (so it can clean mineral scale/deposits and it's compatible with aluminum) plus it's a disinfectant, so it kills bacteria/algae/mold/fungus and those mussels you have growing in there!

If you want to move forward with that, I'll do more research for you. Without knowing exactly what it is, though, it's a bit tough to pick the best cleaning method.
H2O_Doc is offline   Reply With Quote
Old 10-22-2020, 07:16 PM   #12
Guru
 
HopCar's Avatar
 
City: Miami Florida
Vessel Name: Possum
Vessel Model: Ellis 28
Join Date: Aug 2011
Posts: 4,681
I saw the photo before I read your post. My first thought was ď that looks like an aluminum water tankĒ.

Aluminum is a horrible water tank material. Replace them.

The same thing happens in water heaters with aluminum tanks. I always use stainless or glass lined water heaters.

Buy plastic replacement tanks from Ronco Plastics. They make high quality tanks with a heavy wall thickness. They will put the fittings where ever you want them. They make almost 500 different size and shapes of tanks.
https://ronco-plastics.com/
__________________
Parks Masterson
HopCar is offline   Reply With Quote
Old 10-30-2020, 08:28 PM   #13
Member
 
City: Park Rapids
Vessel Name: looking for 1st trwler
Join Date: Sep 2020
Posts: 17
Quote:
Originally Posted by kthoennes View Post
Right there, that's why we never drink the tank water. I don't care how clean it smells and tastes or how clean I think the tanks are or whether there's an inline filter. Even if those deposits are purely mineral, eew.
If that bothers you dont ever work on you supplu lines in a house.
MNdiver is offline   Reply With Quote
Old 10-30-2020, 08:46 PM   #14
Guru
 
catalinajack's Avatar
 
City: Edgewater, MD
Vessel Name: Catalina Jack
Vessel Model: Defever 44
Join Date: Nov 2011
Posts: 1,850
What one cannot see, cannot hurt. Totally a non-issue as to safe drinking.
Quote:
Originally Posted by MNdiver View Post
If that bothers you dont ever work on you supplu lines in a house.
catalinajack is offline   Reply With Quote
Old 10-30-2020, 09:04 PM   #15
Guru
 
menzies's Avatar
 
City: Jacksonville
Vessel Name: SONAS
Vessel Model: Grand Alaskan 53
Join Date: May 2014
Posts: 7,120
Have a look at the second photo in this blog entry!

Finally Leaving Lucaya And Getting To Exuma | AtAnchor.com
menzies is offline   Reply With Quote
Old 10-30-2020, 09:09 PM   #16
Guru
 
Comodave's Avatar
 
City: Au Gres, MI
Vessel Name: Never Say Never
Vessel Model: President 41 DC
Join Date: Jul 2015
Posts: 10,025
We had custom welded plastic tanks made for a previous boat. Worked well but they werenít cheap. But that way I could maximize the usage of the available space.
__________________

__________________
Boat Nut:
If you are one there is no explanation necessary.
If you arenít one, there is no explanation possible.
Comodave is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 01:59 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012
×