How to Tap Plastic Fuel Tank

[95ImpySS]

Hello, I am curious on how to tap into a plastic fuel tank. I have the deck up in my boat and would like to add an extra aluminum fuel tank and connect it to the factory plastic 25 gal tank. I figured I just take a piece of 3/4 fuel line, and connect the bottoms of both tanks together that way the fuel can flow evenly between both tanks. Then connect the the top of the new tank to the vent line of of the plastic tank. I see this done on big trucks all the time and the two tanks will be the same height and less than 1 foot next to each other. I'm just wondering what fitting I could put at the bottom of the plastic tank.

Any tips? Thanks

 

[Bondo]

Re: How to Tap Plastic Fuel Tank

and connect the bottoms of both tanks together that way the fuel can flow evenly between both tanks.

Ayuh,... You Can't do that,... These are Boats,+ it's Gasoline,...
Not Tractor-trailers,+ Diesel Fuel....

 

[Lion hunter]

Re: How to Tap Plastic Fuel Tank

I would not trust a fitting at the bottom of a plastic tank. To much expansion and contraction, the fitting would never seal. I had an old glastron that had similar tanks to what you want but they were both steel an the fitting were brazed on. If you used 2 aluminum tanks I don't see why it wouldn't work.

 

[Mark42]

Re: How to Tap Plastic Fuel Tank

Coast Guard regulations prohibit fittings on marine tanks anywhere but on top. If you want to connect two tanks, do it with a 3 way valve so you can switch between on tank1, on tank2 and off. A 4 way could do on tank1, on tank2, both tank1 and tank2 and off. But do not modify the plastic tank.

Plastic tanks are not easy to tap. Its generally done by spinning a fitting of like plastic at high speed and pressing it into the plastic until friction melts them together. Not something the average person can do.

Fittings on the bottom are a fire/explosion hazard if they leak. If the hose gets a hole, the entire tank will drain, followed by a big boom.

 

[Lion hunter]

Re: How to Tap Plastic Fuel Tank

That's why this site is so great, get alot of brainstroming going on. The 68 Glastron I had, had the tanks above deck under the splash well. They were either oem or made so well thay fit every curve. I never realized that they were prohibited.

 

[95ImpySS]

Re: How to Tap Plastic Fuel Tank

Ayuh,... You Can't do that,... These are Boats,+ it's Gasoline,...
Not Tractor-trailers,+ Diesel Fuel....

That's a waste of a post. Thanks for nothing...

...anyway, thanks to the rest of you, I did plan to do the switching valve but this idea popped into my head and I wanted to check if this was a accepted or legal idea. I figured I'd keep the old tank and the sender and just add 20 gals of capacity. I wont be doing that Thanks again everyone.