Patching a holding tank?

[toocoys]

Our holding tank is approx 30 gallons or so, and its aluminum. It's nearing the end of its life and we do plan to replace it with a polytank, but we'd like to squeeze another year of life out of it, or at least have it carry us until next season.

Currently the inlets look like this crude drawing. The parts where the hoses connect are severely corroded and I cannot get a good seal to keep it from leaking.

What I would like to do is cut the current inlets out, and replace it with a fabricated part like this. Just two aluminum inlets, welded to a plate, that I can then epoxy over the hole that I cut out.

What I'm wondering is if there is a way to do this in PVC, or some plastic material instead of having to track down an aluminum fabricator?

Any suggestions? (And yes I know that doing this is only delaying the inevitable, but as I said we're trying to squeeze a little more life out of the tank before we ultimately replace it.)

 

[RT Firefly]

Greetings,
Mr. t. Piece of cake (almost). You can probably find most, if not all of the necessary fittings at your local big box store. For the plate, a plastic cutting board from the $ store will work IF it can be glued with your ABS or PVC cement. It'll only cost a buck or two to find out. Find the appropriate flat board BEFORE you go and buy all your fittings. Forget about the epoxy to attach. Pre drill the board and use self tapping screws to attach to tank with a layer of sealant. Done.

 

[toocoys]

Greetings,
Mr. t. Piece of cake (almost). You can probably find most, if not all of the necessary fittings at your local big box store. For the plate, a plastic cutting board from the $ store will work IF it can be glued with your ABS or PVC cement. It'll only cost a buck or two to find out. Find the appropriate flat board BEFORE you go and buy all your fittings. Forget about the epoxy to attach. Pre drill the board and use self tapping screws to attach to tank with a layer of sealant. Done.

Didn't even think of that! Thanks RT!

 

[HeadMistress]

Do yourself a huge favor and replace it NOW. The corrosion you can see is the least of it. It will not last another season before failing at a weld or a tank wall...and even a small leak can create big odor problems. The last thing you need is a catastrophic failure when you have guests aboard. And another good reason: it's a lot easier job when the weather cool.

Ronco Plastics Ronco Plastics marine Tanks (no relation to the VegoMatic Ronco) is your best source for a tank. They make TOP quality thick-walled water and waste tanks for a very reasonable price and have more than 400 shapes and 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.

If your hoses are 10 years or anywhere close to that age, replace them too. 10 years is the average working life of any hose because as rubber and plastics age they dry out, becoming hard, brittle and prone to cracking. Raritan SaniFlex hose Raritan Saniflex Sanitation Hose has been on the market for about 10 years without a single reported odor permeation failure--and I've yet to hear of any either--and has the added advantage of being so flexible it can be bent like a hairpin without kinking, making installation a LOT easier that with most hoses. Defender has it for <$10/ft. Raritan Sani / Flex Sanitation Hose at Defender

Finally...my book (see link in my signature...just click on the title) includes step by step instructions for replacing toilets, tanks and hoses WITHOUT making a nasty stinky mess.

--Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

 

[toocoys]

Do yourself a huge favor and replace it NOW.

Well we would if we could, but right now we have more pressing financial matters to tend to, so I need to patch it to squeeze a little more life out of it.

 

[toocoys]

I remembered I have a piece of aluminum at the RV. I wonder if I could use something like this as an inlet to connect the hoses. hmmm....

https://www.westmarine.com/buy/attwood--90-thru-hull-fitting-1-1-4-id-hose--6703292?recordNum=38

 

[Roamer Blue]

RT has your solution.


Sealing the perimeter of the plate, between incompatible materials, is flat, straight and simple, with room to keep adding screws and cheap caulk as necessary. Proper plastic board, matched to the same plastic piping, the glue will bond it all together, no leaks.



Sealing each pipe fitting thru an incompatible material, you need fancier/more expensive fittings to ensure a seal, and still have to caulk and screw the plate to the tank.


Don't mix up your plastics, the glue won't work, and you'll have a mess.

 

[HeadMistress]

I knew a houseboat owner who'd used JB Weld to patch so many leaks in his aluminum holding tank that till the bottom of the tank failed, we speculated that he now had a tank made entirely of JB Weld. The stuff does work. But it can't prevent the bottom of your tank from turning into a colander. So if you can't afford to replace the tank, pump it out and very thoroughly rinse it out and buy a portapotty to use until you can. It's what I would do.


--Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

 

[toocoys]

I knew a houseboat owner who'd used JB Weld to patch so many leaks in his aluminum holding tank that till the bottom of the tank failed, we speculated that he now had a tank made entirely of JB Weld. The stuff does work. But it can't prevent the bottom of your tank from turning into a colander. So if you can't afford to replace the tank, pump it out and very thoroughly rinse it out and buy a portapotty to use until you can. It's what I would do.


--Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

Nah, it’s good for now, we haven’t noticed any leaks on the bottom. I’ve got a plan for a patch that will hold us over. Thanks for your input though. In this case I’m going to deviate.

 

[toocoys]

RT has your solution.


Sealing the perimeter of the plate, between incompatible materials, is flat, straight and simple, with room to keep adding screws and cheap caulk as necessary. Proper plastic board, matched to the same plastic piping, the glue will bond it all together, no leaks.



Sealing each pipe fitting thru an incompatible material, you need fancier/more expensive fittings to ensure a seal, and still have to caulk and screw the plate to the tank.


Don't mix up your plastics, the glue won't work, and you'll have a mess.

We took the tank monitoring gauge out and a repair guy ended up epoxying an aluminum patch over the hole. I though he was going to have to weld but the epoxy worked out well. If I can manage it I’ll do the same with this one and figure out how to form my pipes out of PVC. Maybe there’s a screw type collar or something I can use. That’s why that thru hull fitting looked like a good option.

 

[Maerin]

If you can get the aluminum plate epoxied to the top, that'll work. Rough up the mating surfaces of the aluminum with 80 grit or coarser, and make sure it's scrupulously clean.
Alternatively, you could cut a square hole in the tank, fab a square bolt flange from 1/4" aluminum, tap holes in the flange and get it inside the tank, then fab a rubber gasket to make a flange for your pipe penetration plate on the top of the tank that could then be through bolted like a companion flange. Epoxy is probably your best if you can get a good mate on the surfaces.



For the piping penetrations, I'd use a Uniseal. Make up a plate from say 3/16" aluminum, and cut holes for the uniseal. Can all be field fabbed. You can fab a PVC dip tube and hose adapter out of DWV PVC, don't use pressure fittings, they're too short a radius. I'd use a Sealand smooth hose adapter as it will present less obstruction inside than using a nylon or other type threaded barb adapter. The PVC can slide through the Uniseal and into the tank with a minimum of fittings. Can do the vent the same way if needed.

 

[FF]

The patch is temporary!!

A quart or 2 of Bondo should keep fluids in the tank, the top is seldom highly stressed.

If you worry , pump out more often. When the season ends , do the real replacement.

 

[toocoys]

We have a pump out service that comes every Wednesday.

 

[toocoys]

Well, I’ve decided to let the yacht service repair it. They’ve replaced my lawn irrigation solenoid for the aft Head with a genuine Jabsco solenoid and I’m happy with the cost and quality of work.

 

[FF]

There is a huge difference between a patch and a genuine repair.


Find out which you will be charged for.