Building a water tank

genieskip · #1 (**permalink**) 04-12-2009

A recent article in Good Old Boat described the process and materials used in building a "one of a kind" water tank. It was just what I needed since I am redesigning and rebuilding the main cabin of my J40. Following their instructions and descriptions, I got the potable water epoxy used in the construction and have the project well along. Problem is, the dog (or the gremlins) ate my copy of the magazine before I bought the right kind of potable water safe caulking to seal the fittings and inspection ports. Can someone who still has a copy tell me what they recommend for that purpose? Alternately, if anyone knows what should be used for caulking the fittings that will not leach nasty chemicals into the drinking water, would you pass this information on? Any help would be greatly appreciated.

endeavour33 · #2 (**permalink**) 04-12-2009

ask someone at a tropical fish store they have the same concerns with aquariums, I looked it up and got this :

"For building decorations and aquariums, I use pure clear silicone sealant which is also labeled "For Aquarium Use". Do not use silicone with any kind of algaecide in it (such as Silicone II at the hardware store) as the algaecide is toxic. Let the item dry until you don't smell fumes anymore and then it is safe to put into the tank or to fill with water.

I also use aquarium epoxy (cut piece, knead, use), but it only comes in "stone" or "white" and both colors look like chewing gum in the aquarium. It dries rock solid, however, and is what I use when I will be able to completely hide the epoxied area. It works great for sealing pipe leaks and fittings and for building sum"

tager · #3 (**permalink**) 04-12-2009

I would be weary of using stuff for fish... I mean it is probably safe, but be weary... you are not a fish.

US27inKS · #4 (**permalink**) 04-13-2009

Quote:

Originally Posted by tager

I would be weary of using stuff for fish... I mean it is probably safe, but be weary... you are not a fish.

Salt water aquarium fish are VERY sensitive critters. Corals die for almost no reason at all. You can believe that if it's safe for a reef tank, it's safe for you.

The only thing I would be concerned about is the strength of the adhesive. Aquarium adhesive is designed to seal two pieces of precision fit glass together. No gaps or irregularity. No flexing either. The two part epoxy is great for something that's never going to flex as well. I doubt either will be a suitable sealant for this project.

I know you're already into this project and it's too late now, but why didn't you go with a flexible bladder?

sailingdog · #5 (**permalink**) 04-13-2009

Use this stuff: LINK

Basically, any NSF rated sealant should work. If you did a search for NSF food grade sealant, it'd turn up a lot of solutions... The NSF rating is the key thing for potable water systems.

The tank isn't going to flex... he's built it from fiberglass with NSF grade epoxy by the sounds of it... the OP is looking for a sealant that he can use to seal where the tank fittings enter the tank... the NSF silicone sealant I linked to is designed for pretty much that kind of task.

Quote:

Originally Posted by US27inKS

Salt water aquarium fish are VERY sensitive critters. Corals die for almost no reason at all. You can believe that if it's safe for a reef tank, it's safe for you.

The only thing I would be concerned about is the strength of the adhesive. Aquarium adhesive is designed to seal two pieces of precision fit glass together. No gaps or irregularity. No flexing either. The two part epoxy is great for something that's never going to flex as well. I doubt either will be a suitable sealant for this project.

I know you're already into this project and it's too late now, but why didn't you go with a flexible bladder?

US27inKS · #6 (**permalink**) 04-13-2009

Quote:

Originally Posted by sailingdog

The tank isn't going to flex...

I was more concerned about the fittings than the tank. Actually, I was concerned about what he's going to attach to the fittings and what those hoses would do to the fittings.

Glad you found a suitable sealant for him.

genieskip · #7 (**permalink**) 04-13-2009

Quote:

Originally Posted by sailingdog

Use this stuff: LINK

Basically, any NSF rated sealant should work. If you did a search for NSF food grade sealant, it'd turn up a lot of solutions... The NSF rating is the key thing for potable water systems.

The tank isn't going to flex... he's built it from fiberglass with NSF grade epoxy by the sounds of it... the OP is looking for a sealant that he can use to seal where the tank fittings enter the tank... the NSF silicone sealant I linked to is designed for pretty much that kind of task.

Thanks SD (and others), the NFS tag helped a lot in my search. Sealant ordered and on its way.

sailingdog · #8 (**permalink**) 04-13-2009

Good luck, glad to help, and post photos of the project when you're done.

Valiente · #9 (**permalink**) 04-13-2009

Water sloshes and plastics deform. Does your tank have baffles?

genieskip · #10 (**permalink**) 04-13-2009

Quote:

Originally Posted by Valiente

Water sloshes and plastics deform. Does your tank have baffles?

It is not built out of plastic. It is 1/2" marine plywood covered on both sides with fiberglass cloth & layers of epoxy, then covered on the inside with a special food grade epoxy. And yes, there are baffles. No space is bigger than 30", same as the fuel tank requirement for baffles.

I'll take some pictures as the job progresses and post them later.