Peggie Hall wrote:
Glenn (s/v Seawing) wrote:
Did I read that correctly...urine will destroy an aluminum holding tank?

Yep. It'll destroy ANY metal holding tank, even 316 stainless.

Bummer...my Father just had one made for his trawler. Any way to
prevent this?

Nope. But it's not gonna suddenly disintegrate. The average lifespan of
any metal waste tank is about 10 years. Typically, it'll start to leak
at a weld in seam or fitting within about 2 years...and turn into a
colander in about 10 years.

So you might want to tell him not to panic...it'll be ok for the next
few years. Just keep an eye--and his nose--on it. And tell him not to
bother repairing the first leak...'cuz the first one is always ONLY the
FIRST one. The time to replace it with a good quality thick walled
plastic tank is after it springs te first leak. Till then, he can relax.

Any chance coating the inside with an epoxy coating will help extend
the lifespan? In commercial ships black water tanks ARE often built
into the hull of the ship as integral steel tanks.

Though I'm not fond of the practice myself, sometimes the tanks are
2000 - 3000L and plastic tanks of that size are a bit bulky to fit
into an engine room...

Evan Gatehouse

Somebody wrote:

Did I read that correctly...urine will destroy an aluminum holding
tank?

Yep. It'll destroy ANY metal holding tank, even 316 stainless.

That's why "tank resin" exists.

Lew

Lew Hodgett wrote:
Somebody wrote:

Did I read that correctly...urine will destroy an aluminum holding
tank?

Yep. It'll destroy ANY metal holding tank, even 316 stainless.

That's why "tank resin" exists.

Metal tank mfrs have have been coating holding tanks with all kinds of
things...epoxy, resin... To date there has been nothing that will
extend the life of a metal holding more than a year or two...if that long.

--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://shop.sailboatowners.com/boat_odors/

"Peggie Hall" wrote:

Metal tank mfrs have have been coating holding tanks with all kinds of
things...epoxy, resin... To date there has been nothing that will extend
the life of a metal holding more than a year or two...if that long.

Guess my customers, the heavy chemical industry, are unaware of this
limitation.

Lew

On Sat, 27 Oct 2007 01:23:38 GMT, Peggie Hall
wrote:

Did I read that correctly...urine will destroy an aluminum holding
tank?

Yep. It'll destroy ANY metal holding tank, even 316 stainless.

That's why "tank resin" exists.

Metal tank mfrs have have been coating holding tanks with all kinds of
things...epoxy, resin... To date there has been nothing that will
extend the life of a metal holding more than a year or two...if that long.


I have a thought. It's off the top, but it's worth testing.
Any acidic solution tends to eat metal. Water doesn't even
need to be acidic to promote pin hole corrosion in some
aluminum alloys. Oxygen depleted water is hell on stainless.

But alkaline solutions, in general, don't eat metal so well, or at
all. I have this hunch that waste water rendered slightly high pH
of neutral would help a tank to survive.
Do you have any stories on this topic?

Brian Whatcott Altus OK

Brian Whatcott wrote:
I have a thought. It's off the top, but it's worth testing.
Any acidic solution tends to eat metal.

Not necessarily. Vinegar is acid, but doesn't harm metal...chlorine
isn't acid, but is corrosive and does destroy metal.

Water doesn't even
need to be acidic to promote pin hole corrosion in some
aluminum alloys. Oxygen depleted water is hell on stainless.

But alkaline solutions, in general, don't eat metal so well, or at
all.

Urine can be alkaline or acidic...doesn't seem to matter in a metal
holding tank.

I have this hunch that waste water rendered slightly high pH
of neutral would help a tank to survive.

Waste and water have about the same pH...7-9...so I don't THINK pH is
the key...'cuz the same aluminum alloy tank used to hold water will last
20-25 years.

I'm not a chemist, so I can't tell you why that's true, only that it has
proven to be.

--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://shop.sailboatowners.com/boat_odors/

On Sat, 27 Oct 2007 10:02:59 -0500, Peggie Hall
wrote:

Urine can be alkaline or acidic...doesn't seem to matter in a metal
holding tank.

Well who'da guessed! Dilute uric acid alkaline! I picked out the
Corning pH meter, all set to put it to the test.
But the 3 volt lithiums need changing. Oh well.

I have this hunch that waste water rendered slightly high pH
of neutral would help a tank to survive.

Waste and water have about the same pH...7-9..

??

Thanks for responding

Brian W

On Sat, 27 Oct 2007 23:17:06 GMT, Brian Whatcott
wrote:

On Sat, 27 Oct 2007 10:02:59 -0500, Peggie Hall wrote:
Urine can be alkaline or acidic...doesn't seem to matter in a metal
holding tank.
.....
I have this hunch that waste water rendered slightly high pH
of neutral would help a tank to survive

..-
Waste and water have about the same pH...7-9..

I finally bought the silver oxide cells for my Corning pH meter, and
peed a sample to check - it read 5.5 pH - about where I expect.

But...but..but: I seem to recall that waste mater can soon smell
ammoniacal, and maybe THAT'S the alkaline component?

Brian W