Bertram33 User Forum

My brother is looking to install a holding tank under the v-berth of his 34 foot sailboat. He has found a website that will make him a custom holding tank out of aluminum. He asked me my opinion on whether aluminum would be a suitable choice for a holding tank. I told him I would ask the gang here. Though I don't think I've ever seen an aluminum holding tank, I can't think of why you wouldn't want one. Do you think it would contain odors better or worse than a poly tank? Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]

Given how much time I spend on my boat, and the fact my wife would sell the friggin thing if it smelled like so many boats we see (smell), my view of the holing tank is buy cheap and replace from time to time. My yard did my entire toilet system over when I first bought and they suggested tearing out the tank and hoses after 5 - years. Of course, they got the same message as me from honey, and while I'm not sure it was needed cause we had no smell, I will say that in the grand scheme it was small money and that thing was friggin gross - and we are religous about dumping etc.

So what is your holding tank made of? Polyethylene? Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]

Doug, I would presume the tank is for waste? If so, I'm told neither aluminum nor stainless are good materials due to the corrosiveness of the contents and the oxygen depleted environment. I was also told that standard commercially avialable Polyethylene is to thin to prevent odor permeation over time. A Custom thicker Poly tank was recommended but it wasn't cheap. I subscribe to Gmarties theory- by cheap and dispose because reapirs aren't an option in my book.

Doug, On my last boat I needed a tank that would fit under the companionway stairs and had to make a custom one. I used stainless and lined it with POR 15. The POR 15 guys swore that the stuf would hold up to anything and so far it has. It's been about 8 years now without a failure. If I had to do it again, knowing what I do now, I would probably use aluminum instead of stainless and still use the POR 15.

Everything I've ever read said to not use aluminum or stainless for holding tanks. It is just to corrosive an environment for those metals. I know that POR is great stuff, but we don't all have Frank's skills. So now you are relying on your own prep & application of a chemical barrier to keep the nasties out of your bilge. That said, the negative on the cheapy tanks is that they are only 1/4" thick. To prevent odor permeation , you need a minimum of 3/8" thickness such as the Ronco Plastics tanks. That's my $.03 worth. (inflation) Al

Al, Everything you say is correct but I assume Doug's brother needs a complicated shape that would be difficult (read expensive) to have made from plastic. That's the way it was in my case. Anyway, the POR 15 doesn't take much skill to use and it could make a non-suitable material work for several years anyway.

Doug... I did a fairly extensive search about heads and holding tanks, and installation of them in a simple system. I have a writeup I prepared for someone on the B31 forum that I can dig out if you want it. Several points to mention... The primary reason holding tanks stink is because they don't have large enough vent lines. The anaerobic (without air) decompisition products of stuff stored in a tank will create stinky gasses that get into the boat via leaks (not often because these can usually be seen and repaired), migration through walls of hose (the major source of odors), and when vent tube gasses come back into the cockpit after leaving the boat. Larger vents allow aerobic (in the presence of air) decomposition products to form in the tank.. these are less stinky. Small 1/2" vents are too small to permit aerobic decomp, it is recommended that at least 3/4" fittings be used.. I used 1 1/2" PVC pipe and sanitary head hose everywhere for everything, even the tank vent line. The tank itself should be poly, and a minimum of 3/8" wall thickness. All fittings except the last choice drain plug, should enter and leave the tank from the top.. with dip legs for the suction lines to the deck pumpout and offshore pumpout. I found that Ronco is the actual manufacturer for many of the places who sell holding tanks.. so I went to them directly. They have tons of "standard" tank molds in stock, but when you order you have to specify the size and location of every fitting. (I went with all 1 1/2" female. They were great to work with, good delivery, other than the dip legs (which I now realize can be made from off the shelf PVC pipe fittings) there was no charge for the 1 1/2" fittings. I have a sketch of the piping system and even a pic of the tank.. let me know how far you want to go with this little discussed but very important subject. Frank B - IRGuy@aol.com "Phoenix" 1983 FBC Wilmington, NC

Thanks for all the input. Frank Price hit the nail on the head though as it will need to be a custom tank to fit under his v-berth. What is POR 15 and who coats the tank with this stuff? Did you do it yourself FRank or did the tank manufacturer do it? Whom did you use to make the tank? Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]

Doug, Take a look through this catalog. Al http://www.ronco-plastics.net/marinetanks.html

Doug, POR 15 is a gas tank seaaler made to seal gas tanks (metal ones) against all kinds of fuels. Very tough stuff, easily applied by dumping a quart of it intothe tank,sloshing it around and emptying out the residue then letting it dry for a few days. I made the tank myself.

I this is what he'll be going with: http://www.oceanlinkinc.com/tanks/waste-water.htm Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]