Integral water/waste tank fittings?

[willy13]

I plan on building custom integral water and waste tanks into a fiberglass hull to maximize space. What type of fittings does one use for hooking up the various hoses? My understanding is that epoxy will not stick to PVC, so fiberglassing PVC NPT fittings is not possible. Same with nylon and other plastics? Are there bulkhead fittings with gaskets that will work? Or should I source pultruded fiberglass tube of the correct diameter and fiberglass it to the tank.
Thanks,
William

 

[Bmarler]

I looked around for a while and there seems to be a lack of information on this. My thought was to either, glass on a good size disc of gpo3 or similar after making npt threads in it, or maybe look at this threaded coupler: FRP Threaded Couplings - 2" Diameter 6" Length Composite Fiberglass Coupling
The six inch coupler could be cut in half and then you would have two female threaded entry fittings you could glass in.
Another possibility using gpo3 sheet would be to install a maralon through hull fitting in a piece of sheet stock and glass that on.

 

[Comodave]

I have used epoxy to stick to PVC. I called West Epoxy first to make sure it was ok. Do a test first to make sure you are happy with it.

I would make sure that the epoxy and glass are safe for drinking water.

 

[MYTraveler]

I have used epoxy to stick to PVC. I called West Epoxy first to make sure it was ok. Do a test first to make sure you are happy with it.

I would make sure that the epoxy and glass are safe for drinking water.

I, too, have had success with epoxy/pvc connections, but there are better adhesives for creating a good bond with PVC. Perhaps there is confusion of PVC with polyethylene?

 

[willy13]

https://support.jamestowndistributors.com/hc/en-us/articles/1260801911490-Is-epoxy-compatible-with-other-Fiberglass-Reinforced-Plastics-FRP

Thanks for finding those threaded FRP fittings, it looks like they should work.

I am amazed that I haven't tried epoxy experiments with PVC yet, as I have scrap PVC all over my garage and I always mix too much epoxy...

I might pour some thickened epoxy and try tapping it myself.

The tank will be coated with a drinking water safe epoxy, though we only use bottled water for drinking.

 

[rslifkin]

Integral fiberglass tubes would work fine. Otherwise if you leave access plates in case one ever needs to be replaced, I'd consider just using a thru hull or bulkhead fitting installed with sealant.

As far as drinking water, when I built our water tank I coated the inside with Aquatapoxy A61. It's a drinking water safe epoxy (leaves a smooth, hard, white finish), but it's awful to work with. And then I added filters to the water system including carbon filters to reduce concerns about anything leaching out of the tank (and we didn't drink the water for the first couple of months just in case). Most stuff that can leach out of epoxy can be removed by a carbon filter with adequate contact time.

 

[lwarden]

Consider building stainless plates with welded pipes for all hose fittings and screw/5200 to the fiberglass surface. That way they can be removed if necessary.

 

[rslifkin]

Consider building stainless plates with welded pipes for all hose fittings and screw/5200 to the fiberglass surface. That way they can be removed if necessary.

That would work for a water tank, but I wouldn't use anything metal for a waste tank.

 

[lwarden]

This is how the waste setup is done in my boat, 23 years and no issues, but the plate and tube assembly is located on the top so not submerged in waste. I agree stainless is not ideal but I think in this setup it will likely last the life of the boat. Of course this port plate could be made of FRP and G-10 tubes easily enough if you want to avoid stainless.

 

[willy13]

If anyone is curious, this is a picture where the water tanks will go. I will enclose the nook where the oval cut outs are on both sides. For the most part the space is not used because it's hard to get at. Also it frees up a large space near the sink where the current 50 gallon poly water tank is. Each side is about 23 gallons so a total of 46. The tanks will be connected.

I don't know if it will be noticeable, but having as much weight on the sides of the hull as possible should help slow the roll of a full displacement hull. So I have read.

 

[lwarden]

That's an odd aspect ratio for a black water tank. I would expect it may have issues with solids buildup over time and turning an existing space like that into a sealed tank might prove challenging.

 

[Comodave]

I absolutely would not do this. I would go to Ronko and buy some quality holding and water tanks. They have hundreds of stock tanks and will install fittings where you need them. It will be difficult to clean out the holding tank and I am not sure I would trust drinking water in this type tank. And if you don’t get a good layup in the holding tank and it fails when it is full, ugh…

 

[willy13]

That's an odd aspect ratio for a black water tank. I would expect it may have issues with solids buildup over time and turning an existing space like that into a sealed tank might prove challenging.

If I do integral tanks, this area will be water tanks. Its still not ideal that there is only 13 inches of height for efficient use as a tank. But my current water tank is only 3" taller so.

 

[willy13]

I absolutely would not do this. I would go to Ronko and buy some quality holding and water tanks. They have hundreds of stock tanks and will install fittings where you need them. It will be difficult to clean out the holding tank and I am not sure I would trust drinking water in this type tank. And if you don’t get a good layup in the holding tank and it fails when it is full, ugh…

I am considering this as they do have some long slender tanks that would help me free up space in the galley. But from a space standpoint integral tanks would be ideal. I should of mentioned this is a 23 ft custom trawler. So space is limited.

 

[lwarden]

Have you considered a custom bladder for these tanks? I was involved with a 46' converted racing sailboat in the 80's which had a bladder waste tank under the floorboards. It worked just fine and seemed to pump out without any issue. I would think you could get most of the volume of that area with a bladder with little to no effort on the fiberglass end.

 

[O C Diver]

I wouldn't do a built in waste tank. Considering the contents, I would prefer a stock size tank with a remove and replace pathway. Can't imagine trying to repair or interior coat a leaking waste tank. Remember, absolutely nobody ever expected a tank they installed, to leak!

Regarding built in water tanks, if you will have an inspection port, why not have the fitting with a suction tube built into the plate. My boat had screw in, oring sealed, inspection ports on the top of the water tanks. I see no reason not to have a draw tube that is easily removable, built into the lid. It certainly makes sealing the inspection port easy if it's mostly out of the water and not under pressure.

edit: After some additional thought, I would probably attach a flange for the draw tube, on the top of the water tanks next to my inspection port. Pretty easy to through bolt a flange next to an inspection port.

Ted

 

[Hook and a screw]

I wouldn't do a built in waste tank. Considering the contents, I would prefer a stock size tank with a remove and replace pathway. Can't imagine trying to repair or interior coat a leaking waste tank. Remember, absolutely nobody ever expected a tank they installed, to leak!

Regarding built in water tanks, if you will have an inspection port, why not have the fitting with a suction tube built into the plate. My boat had screw in, oring sealed, inspection ports on the top of the water tanks. I see no reason not to have a draw tube that is easily removable, built into the lid. It certainly makes sealing the inspection port easy if it's mostly out of the water and not under pressure.

edit: After some additional thought, I would probably attach a flange for the draw tube, on the top of the water tanks next to my inspection port. Pretty easy to through bolt a flange next to an inspection port.

Ted