I Thought my Boat had a Pretty New Holding Tank

[n8kraft]

I recently bought a Cheoy Lee Offshore 41. It had the holding tank replaced in 2006 with a custom made aluminum tank to fit in under the master berth around the hull. When I was cleaning the bilge with a shop vac I found about 6 inches of sludgey stinky water. Yup, the tank broke. I disconnected all the hoses and found that the input elbow was badly corroded. I'm looking in to getting a ronco tank to replace the aluminum one with, but am considering another custom made metal tank.

Does anyone have experience with keeping an aluminum holding tank from corroding?

[dohenyboy]

Yes, carefully remove the tank, and carry it to the nearest dumpster.
Aluminum is not appropriate for a holding tank.
Go to tank depot, or there are people who will weld a plastic tank to fit

[peghall]

Aluminum--ANY metal, even 316 SS--is a bad choice for sewage holding 'cuz urine is so corrosive that it typically eats through a weld at a seam or a fitting within 2-5 years and turns the tank into a colander in an average of about 10 years. Coating the inside of the tank with epoxy can sometimes extend the life of a metal tank, but only for a short time. So go with a Ronco tank...it'll last at least as long as the boat stays afloat.

Soap, water and bleach will not eliminate the odor in your bilge...for that, I recommend a product called PureAyre PureAyre I found it at the Seattle Boat Show about 6 years ago, took some home to test and it knocked my socks off...the only product I've ever found that can not only permanently eliminate "organic" (sewage, mold, swamp etc) odors, but ALL odors including diesel and smoke.

So buy a gallon of PureAyre (the "household" version is the least expensive and works just as well as the "marine" version) and a 1 gallon garden pump sprayer jug (you COULD use a trigger sprayer, but your hand will get very tired)...clean up the site very thoroughly with plenty of detergent and water...remove all the excess water with a shop vac, sponge and bucket, whatever...when everything is pretty much dry, no more than just damp, coat every surface, nook and cranny in the affected area with the PureAyre. DO NOT RINSE!! Just let it dry, leaving all hatches open--even turn a fan on if you can--for at least 24 hours. If you still have any odor, you missed a spot.

Btw...PureAyre is safe for use around children and pets...and food.

Give me a shout via email if you need help spec'ing out the new tank fittings.

Oh...and fwiw...I have no vested interest or axe to grind whatever in any product I recommend.

[HopCar]

Peggy, When you recommend a product that I don't have in my store, I have to take a look at it. I guess I'll have to stock it. The website says it works on flatulence! Do you think drinking it before eating the beans would work? Seriously it sounds like it's worth trying. We had a bait freezer go down one night. I think it might have been nice to have handy the next morning.

[peghall]

Oh good...you survived the Miami Boat Show!

PureAyre would indeed have been an excellent product to have on hand when your bait freezer went down. I learned just how good it is when when the dock power went down, blowing my main breaker, on a Tuesday in July when I had a freezer full of steaks that I didn't find till Saturday morning. That was the last time I ever left meat in the freezer on the boat.

Amazon has gallons of the household version for $34.95, which is considerably less than PureAyre's direct DEALER price!

[n8kraft]

Peggie, thanks for the reply! I have your book and already used the Raritan CP. It didn't completely remove the odor, so I'll try the PureAyre. I received a quote from a plastic welding company here in San Diego for $1500 to weld a new plastic tank. Yikes! I'm going out of town and will be sizing the tank next week.
I can fit a 20 gallon rectangular plastic tank under the cockpit, or in the original location without cutting holes in the supporting bulkhead under the berth where the old tank was. That's not a big tank for a 41' boat, I'm shooting for 30+ gallons.


Some interesting things I found from the previous installation, there was a hole in the top of the tank, just covered in duct tape


The hose connection completely corroded away


And this is me after getting the tank out.

[peghall]

There are other companies who make welded PE PP tanks for a LOT less than $1500! But before you commission a custom tank, I'd check the Ronco Plastics catalog Ronco Plastics Marine Catalog They make TOP quality thickwalled (at least 3/8") rotomolded tanks for a very reasonable price and have more than 400 shapes/sizes, over 100 of which are non-rectangular...and they install fittings in the sizes and locations specified by the customer when they make the tank. It appears from your photo that yours in the dumpster is rectangular, so you should have no trouble finding one in their catalog that'll work for you. I'll help you spec out the fittings sizes and locations if you want to email me.

[jr_spyder]

I've been going through a similar project replacing a horrible soft bladder tank that was leaky and smelly. I went through all the pre-fab tanks on Peggy's advice and certainly some would fit but not optimally in my space. I had a custom tank made by Dura-Weld. It's 22 gal and cost about $450. The owner answers the phone when you call and in my case improved on my design. Had the perfect tank in less than 4 weeks. Great experience and product.

JR

[Cheechako]

Originally Posted by dohenyboy

Yes, carefully remove the tank, and carry it to the nearest dumpster.
Aluminum is not appropriate for a holding tank.
Go to tank depot, or there are people who will weld a plastic tank to fit

+1 yep.

[sy_gilana]

Yep. Had the holding tank smells too, but NOTHING beats my Jack Russell terrier's farts after she ate rotten duck eggs. Dats Chemical warfare stuff!

[hellosailor]

I once left an aluminum camping pot in the kitchen sink overnight, with some salted pasta water still in it. Found pinholes in the pot the next morning.

So aluminum? Depending on things like the alloy, whether the welder mixed alloys, what's in the tank...Aluminum might not be the best choice for a holding tank. Aluminum is fire resistant. Plastic is not. OTOH plastic really tends to be corrosion-resistant. Salt, sewage, acids, no problem there.

[Georgianbaysail]

Stainless steel holding tanks are far better than aluminum or plastic as there is no odor with stainless steel tanks (especially if it's under your bed)
I also think aluminum cooking pots and pans should be banned ( just saying )

[peghall]

You're half right...SS is better than aluminum, and arguably better than cheap thin walled plastic waste tanks. And it's an excellent choice for water holding,

But NO metal, not even 316 SS, is recommended for sewage holding 'cuz urine will eat through it. Average lifespan of any metal tank is only about 10 years...which is usually just about long enough for it to become the next owner's problem and let the owner who installed it believe it was a good choice.

[n8kraft]

I'm going to put in a plastic tank. I may enlarge the area that the tank goes in and buy two tanks to be plastic welded in to one in an L shape to maximize storage area. We'll see how it goes, and I'll post more as the project progresses. In the meantime I'm going to get some sanitation hose from a friend with a Port Supply card to keep cost in check.

[n8kraft]

I've thoroughly scrubbed the inside of the bilge and took out a lot of the paint using a scraper. I cleaned inside with the PureAyre that Peggy recommended. It worked great!

There was still a small bit of residual odor from where blackwater came in contact with plywood and most of the bilge paint came off. I've sanded and repainted the affected areas.


I bought a new tank from Ronco direct from the factory. They put all the fittings in I wanted right there at the factory. I have two inspection ports because I was afraid that I may have retaining pieces that go over the tank edge.


The new tank fits in the bilge. I'm goign to be wrapping up the project in the next few evenings after work. So far I've built a supporting structure out of wood for the tank to sit in and am adding supporting frames underneath between the bulkheads to support the weight.

I'll post more as the project wraps up. Thanks everyone for your help and insight.