Larger Holding Tank for Catalina 34 MK II

[Peggie Hall]

A stainless or aluminum tank is ok for water or fuel, but you do not want a metal waste tank because urine is so corrosive that it typically eats through a  weld in seam or fitting in about 2 years and turns the tank into a colander in an average of 10 years. And it doesn't seem to matter whether the tank is pumped and rinsed every day that it's used or only pumped when it's full and rarely rinsed at all, the average time span is the same.  You only want to do this once, so go with plastic!

However, Columbus got THREE boats across the Atlantic with less agonizing over where to install water tanks than you're investing in just ONE waste tank!  I'm starting to think that the best possible solution for you would be a self contained system...iow, an "MSD" (designed to be permanently installed, fitted for pumpout . A 6 gallon model holds 50-60 flushes...you'd need a 30-35 gallon tank to hold that many from a manual or electric toilet. A pumpout line and a vent line are the only plumbing needed, unless you want to add a y-valve and overboard discharge pump...you wouldn't have to give up ANY storage...no moving parts, so -0- maintenance...clog proof...easy to rinse out...and all at a cost of less than $200. Thetford even makes an "electric" one that runs on AA batteries! 

Check out the Thetford 365MSD and 465 MSD.

[cmainprize]

A well built 316 stainless tank also welded with 316 rod (wire) will last much longer than two years.  Many of our club members have them and have not had issues in 10 plus years.  The killer of stainlesss tanks is chlorine.   It reacts with the chromium and self destructs.  Either from head products or people trying to clean them.  If you think stainless rots because of urine exposure, ask for a tour of your local water treatment plant and check out the tanks they have and the plumbing they use to transfer waste.  Hint, it will be metalic and shiny. 

I am sure poorly built tanks rot much faster, but it will be a stainless tank in my boat. 

If it leaks, I will be the first one to let the board members know, and say peggy was right.  I may even expoxy coat the inside of the tank prior to welding on the top, but I will see what the tank builder (stainless outfitters) thinks about it first. 
My rough math works out to around 25-26 gallons using the available space in the original location.

[cmainprize]

I forgot to add, check out the toilets in the jail cells next time you happen to be in one.  They are also shiny and metalic (read stainless).  I wonder if they replace them every two years because they turn into colanders? 

No argument from me that plastic tanks are great, but they are not the ony way to go.  Do your reasearch, no one has all the anwsers.

[Stu Jackson]

I forgot to add, check out the toilets in the jail cells next time you happen to be in one.  They are also shiny and metalic (read stainless).  I wonder if they replace them every two years because they turn into colanders?  

You might be mixing apples and oranges here on this one.  The heads in jails are there because porcelain will get destroyed in one day.  They are there to avoid breakage.  Agreed that the siphon contains water all the time.  Having designed a series of new jails in the mid-80's I apologize that I do not have the specs for the units handy anymore, but I am sure that they did not have seams and welds on the corners, which appears to be the issue with using metal tanks for holding tanks.  Please also note that Peggie notes that urine is the killer.  Urine is rarely found sitting in the bottom of water closets, 'cuz they have these things called flushes, right?  Clear water is not hardly as corrosive as urine, which I believe is her point.

"Do your research, no one has all the answers."  One of the nice things about having registrants that have WRITTEN books on specific subjects is that the research has already been done for you.  At least in this regard. If you don't think she has "all the answers" on this subject, please find me someone who has better experience.  Other than your dockmates...

Somehow, it seems to me that the "expert" on boat systems in this regard should receive credit for knowing her subject.  If Peggie says don't do it, I wouldn't, not in my boat.

Your boat, your choice.

[Stephen Butler]

Do the chemistry and then store human waste in plastic.  Whether 2 or 3 or 5 years, ss holding tanks will eventually leak.  Again, its the chemistry.  We watched a custom built ss holding tank being removed and replaced this past summer from an Island Packet.  The owner had the tank for 4 years, built at one of the better ss shops, x-rayed welds, etc. in Florida.  Interestingly, the ss fabricator had warned him not to go ss for this application, but as everything else on his boat was ss, he decided to give it a try. Go plastic.

[Peggie Hall]

Stu, he'll just say "anyone can write a book, doesn't mean they know what they're talking about."  And he'd be right...half the boat maintenance books out there are full of bad information, especially when it comes to sanitation systems.   He's also right that no one has ALL the answers, and I don't pretend to. But after 25+ years in the marine sanitation biz, I do know quite a few of 'em and I also know where to find the answers I don't know...Way over half my reference files are saved replies from various experts.  And the consensus in the marine industry is that metal is a bad choice for waste holding. When it first became necessary to install holding tanks, almost all the major production builders went with aluminum or steel because it cost 'em less and they considered it to superior to plastic...but by 1990--only 10 years later--there are few if any builders left who use metal for waste holding tank. 

Grand Banks and Kadey-Krogan have always installed fiberglass tanks...but with stainless steel inspection port covers in which stainless fittings were installed, including stainless pick-up tubes on the discharge fittings. After about 5 years, owners start trying to find out why their tanks seem to fill up almost immediately after pumping out...and learn that the pumpout isn't able to pull anything out because the pickup tubes have either turned into colanders or actually corroded through completely and fallen off...they're all replacing the metal plates, fittings and tubes with PVC.

Catalina has never used metal...Ronco Plastics has supplied their water and waste tanks for at least a couple of decades. Doncha think that they'd be using metal tanks if metal were a good choice???

But, Cory m'dear...it's YOUR boat...and it's ok with me if you want to put a cardboard box on it for a holding tank.  If you do, please let us know how it works out. 

[TonyP]

Fred
Why couldn't you recess the pipes ie; have cut outs made into the aft end of the new tank? This way you don't lose as much storage.
OK it would mean a bit more fabricating. What I suggest is say a 100x100x100mm (4"x4"x4") cube cut out of the top/aft/stbd corner of your new size tank for the inlet pipe and say the same at the bottom for the exit pipe. This would only lessen the tank by 2 litres or 1/2 gal approx. Of course these sizes could be adjusted to suit your installation.
cheers
Tony
PS could the SS issue change  with the different SS grades 316 & 304 (and there are higher grades). Here in oz most of our public urinals are SS and not all looked after that well but seem to last forever

[cmainprize]

Mrs. Hall,
Your right on several of your comments.  Many published authors are fools and their work should never have been published.  This does not apply to you.

Yes, Plastic is the best material for a holding tank! 

Yes, Stainless will eventually leak!

What I am saying is a well built tank, constructed with the proper materials, and only subjected to human waste will last a long time.  I am aware of SS tanks that have failed very early, I can only speculate why.  I do not agree that SS tanks are not an option.  I would refer board members back to their local water treatment plant for a tour.  Miles of stainless everywhere.

My first choice would be a plastic tank, but I can't seem to find one, production made or custom made that will give me the increased capcity I need. 

Disagreement, does not equal disrespect, just a different opinion.

[Stu Jackson]

Very nicely put, Cory.  Re the sewage treatment plants, I designed a laboratory hood for one plant in our area here, but that was years and years ago, in the mid-80s.  I do recall, however, that the materials needed for the hood exhaust ductwork had to be "special" stainless steel.  As you are undoubtedly already aware, there are a variety of different stainless materials, and we had to be very specific in the specifications for all of the hood materials, ductwork and fan, as well as the electrical and plumbing materials.  Have you selected the ss you will use?

[cmainprize]

After many dicussions, prototypes, and more prototypes Fred and I finaly got our new tanks made.  We went with a 3/8 inch welded poly tank made by MAS plastics in Whitby.  Cost was $700.  I meassured the capacity of the old and new tank twice just to be sure.  The old tank holds 15.3 US gallons.  The new tank holds 27.7 US gallons, or a 81% increase.  The opening for the locker needs to be increased slightly to get the new tank in.  I will add some pictures when I get in installed.  We found our family of four could go around 4-5 days on the old tank, the new tank will allow us to make it a week prior to needing a pumpout.  The vent fiting was moved to the forward end of the tank and will exit into the locker forward of the tank and be routed to a thru hull mounted just below the rail.  The fiting size was increased to 1 inch but I suspect I will need to reduce it to 3/4 to get the thru hull to fit above the above the forward hanging locker.  I will never recover the cost of the tank due to reduced pumpouts, but I won't need to plan for pumpouts quite so often and get to enjoy more time enjoying ourselves, so to me it's worth it.  Pictures attached.

[Jim Hardesty]

Nice, thats what Catalina should have done.  One question.  Why no inspection/cleanout port on top?
Jim

[cmainprize]

I was going to add this sensor (pic attached)  it comes with the flange and the ring and would work as a cleanout/inspection port at the same time.

[Roc]

Cory,
Why not use the tank gage system advertised here:
http://c34.org/bbs/index.php/topic,2682.0.html


This has no parts that go into the tank that can get fouled up.  I have the original Accu-gage, which was the precursor to this. It works great.

[Peggie Hall]

Cory,
Why not use the tank gage system advertised here:
http://c34.org/bbs/index.php/topic,2682.0.html
This has no parts that go into the tank that can get fouled up.  I have the original Accu-gage, which was the precursor to this. It works great.

That's the one I'd recommend.  Dennis provides the best customer service on the planet, too.

[Roger Blake]

Cory--I recommend extreme caution in installing that new tank on your boat. Perhaps you need a test boat, like, well, mine.  Nice tank.