Aluminum Holding Tank????

[hcalmar]

We have a 1979 Hatteras 37c that carries 330 gallons in the cockpit saddletanks with an additional 90 gallon aluminum tank centerline between two engines. The only "holding tank" is a 35 gallon bladder outboard of the port engine. I have a family of five with a Galleymaid pump which I understand pushes about one gallon per flush through the system. The centerline tank may have come from the factory. The blueprints are not clear but it appears that it has been inserted in the original centerline holding tank which had its top cut off. There is foam at either end but it fits snugly side to side.

The centerline fuel tank has not been used for seven years. I understand that aluminum makes a lousy holding tank because of the corrosive nature of what goes into it. If I didn't have so many projects to undertake, I would pull the aluminum tank, substitute a 45 gallon + sea-land tank and work up to a full vacu-flush system in the future. I was on a Carver the other day which I noticed had an aluminum holding tank. Apparently, this is not uncommon on entry-line boats. It has caused me to rethink my priorities.
It would be incredibly easy to hook up the existing tank to the waste system and I would have some nice capacity, particularly useful with the galley-made pump. The fuel fill will work perfectly for the input hose. I can use one of the fuel lines inputs as a vent and will need to add a pump out hose which happens to be right next to the fuel fill on the port side deck. If I can get three, four, or five years out of the tank before something happens, and as I mentioned, it is sitting inside the frame of the old holding tank anyway, I can focus on other issues and delay undertaking a major project.
Thoughts? Hal

 

[luckydave215]

My Hunter sailboat had an aluminum holding tank and it lasted at least until I sold the boat when it was 13 years old. That being said, I always viewed the holding tank as a bomb just waiting to go off. I would have changed it for a polyethelene tank except I would have had to saw through a structural bulkhead to do so. Don't you just love cheap boats? I got lucky....you might not.

 

[captddis]

I too have seen the aluminum tanks on the Carvers. I could not believe it!
If you do not mind sacrificing your tank, go for it. But I doubt you will get much life out of it. The Carvers I have seen with the aluminum tanks also had vacuflush heads that use fresh water so the corrosion is somewhat less. If you need to get the season you can probably do that , any more is a crap shoot. [ pun intended}

 

[AquaNav77]

All aluminum Burgers and Browards have aluminum holding tanks and have withstood the test of time.

 

[Avenger]

Lest we forget there are many different alloys of aluminum. Some are more corrosion resistant than others. Some are more expensive. Which do you think Carver uses? Which do you have? Unless the markings are still on the tank you can only guess.

 

[hcalmar]

I had ocassion to take a picture this afternoon of the centerline tank.
Hal

 

[jim rosenthal]

With all due respect, I would not do this. If the tank fails and leaks, you will be in deep doodoo. Seriously. This is one chance I would NOT take. Do anything but this.

 

[Nonchalant1]

Your current holding tank is a bladder? Sounds like none of this is up to Hatteras standards, so in the long run, the best thing to do is to re-glass a top onto the original tank and set it back up as your holding tank. I'd add baffels too.

In the short run, maybe the aluminum tank will hold for a season, or if the bladder works, why not put a bladder inside the aluminum tank as your second tank? At least if something fails, the whole thing is inside the original Hatteras fiberglass tank (without the top), so if you get into deep doo-doo as Jim points out, the doo-doo will be contained inside the current tanks.

Doug

 

[Genesis]

Yeah, I'd pull the aluminum tank and glass a top back on the original shell. That wouldn't be difficult to do and it would definitely solve the problem for you.

 

[34Hatt]

I agree bite the bullet and go with glass plus you would need a pump out on the aluminum tank. Part of my original glass water tank was converted to holding and it worked out great better then plastic which the odor can come thru with time.

 

[AquaNav77]

As to the inquiry, as to the specific alloy I can answer that according to the Burger and Broward specifications, alloy 5061 is used for the holding tanks. I have no idea what Carver uses.

 

[REBrueckner]

My general experience with "quick fixes" is that they are a waste of time unless temporarily correcting a serious problem so you can get home. Aluminum is like stainless in one respect: there are so many alloys as to thoroughly confuse what you might be installing/buying/repairing. All it takes is a pinhole to start the stink!!

 

[ADaily3224]

Hal.

I agree with getting the aluminum tank out of there and rebuilding the fiberglass tank. You may want to check with Sams to see if they have the original top plate with the intake and stand pipe pump out fitting. There was also a vacuum gauge that informed you when the tank was 3/4 full, you'll want that too. It was a great design to begin with and with new hoses there won't be any odor issues. The plate that has been modified for a fuel tank on your boat won't work for waste, even if you did decide to use it. No stand pipe for pump outs that I could see. There's nothing that can ruin enjoying your boat more than a messed up sanitation system. I wondered if Hatteras put their holding tanks deep in the hull to keep the waste cool to prevent bacteria growth and more gas and odor?

Tony D

 

[hcalmar]

The Tank is out. Here is a picture. Where would you go to have a plastic replacement made? It is 57.25" long, 20.5" wide and 22.75" high. Clockwise from the top the run is 20.5", 16", 12", 12",16". Iwonder if there are any prefab and I would prefer if it wasn't so high- I don't need 90+ gallons for a holding tank I think 45 would do. By the way It is a really well built aluminum fuel tank in excellent shape if anyone is interested
Hal

 

[luckydave215]

Most decent plastic fab shops can make you a (hot air or ultrasonically) welded polyethelene or polypropylene tank.
Re aluminum alloys: The best alloy to use for a tank exposed to water is 5086, but it's expensive and hard to get. Quality aluminum workboats are fabricated from this alloy. The tanks in Burgers are likely 5356 or 5061. A cheap ass Carver probably has the tanks made from 5356, or worse, 6061.

 

[DeeRow]

I've been considering buying a holding tank from these folks, http://www.tank-depot.com/product.aspx?id=158. I currently have a 40 gal. holding tank but have determined that it is not enough. Looking for the largest that I can fit, hoping that I can put in a least a 90 gal. Between Christmas and New Year's, we cruised the keys. With 5 people aboard, we need to empty the tank every day. During the entire trip we were never 3 miles off shore to legally dump the tank. Finding pump out stations was a challenge. I'm going to make a mock up of a tank from cardboard to determine that largest that I can fit before I order.

Mark

 

[34Hatt]

Check into http://www.ronco-plastics.com/ I got a water tank from them they were great to deal with and nice heavy wall tank. They also put all the fitting where I wanted them.

 

[hcalmar]

I have the intercoolers off for cleaning and removed the center tank. Yesterday we removed the foam that held it in, exposing the old glass tank. The top was cut off. I do not think I have the time, $$ or skill to rebuild the fiber top. I can put in a false floor( should i refoam under it) and insert a 40 gal Todd tank. Do you think I could 5200 a starboard top on the old tank and make it work? Are the sides just to thin not to leak? I could use a small screw. Any other suggestions? I have attached pictures. Thanks
Hal

 

[luckydave215]

I believe starboard is polyethelene and therefore un-gluable. Someone speak up if they know otherwise.

 

[spartonboat1]

I sure would Steph Mc at Sams a shot...he is a walking encyclopedia on correct fixes- he may know who makes the Hatt tanks or may know of a replacement...also, Tom Slane gets major attaboys on here as well...worth your time and the cost of the calls, I would say...JMHO...