PVC gas tank question. Please help

Discussion in 'Motorized Bicycle General Discussion' started by taddthewadd, Feb 15, 2010.

  1. taddthewadd

    taddthewadd New Member

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    I have been looking for three hours through the forums here to figure out an alternative fuel tank. I really want to make one out of PVC but I can't seem to find a definite answer if the PVC will stand up to gasoline. Some posts say yes and some say no. I want to use PVC because it is easy to work with but I don't want to take a chance on ruining the engine or something else. Can anyone shine some light here? I know there are some of you who have had PVC tanks for a while. How are they holding up? Thanks in advance.
     
  2. atombikes

    atombikes New Member

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    Interesting concept. Are you talking about using, for instance, a 3" diameter pvc pipe with end caps glued on? What would you use for the filler cap, and how would you incorporate that? Not sure if putting gasoline in pvc is "a really bad idea (tm)" but it may be illegal depending on where you live?
     
  3. Cannonfish

    Cannonfish New Member

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    Tadd, definitely an interesting idea. I'm playing with ideas for alternate gas tanks as well, so I got on Google and here is a summary of the first three results.

    1. One website (Chemical Resistance Chart - Jensen Inert Products) describes PVC's gasoline resistance as "good".

    2. Another website shows where a guy did a 54-hour gasoline immersion test and decided the same thing (SpudTech Archive • View topic - PVC Pipe Gasoline Resistance Test).

    3. Here is a Wiki question (Can PVC pipe be used to handle gasoline and will the regular glue used hold? - Yahoo! Answers), I don't have any idea what the qualifications of these people are, but they all seem to be in agreement.

    I think the most definitive way to determine the gas resistance of a PVC tank would be to go for it - build it, keep an eye on it to ensure its safety, and then us how it went :).
     
  4. taddthewadd

    taddthewadd New Member

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    I am going to try it. Connonfish, thanks for the links. That gives me the confidence to do it. And as for atombikes question, I have seen on threads here people threading the pvc with a tap and using brass plumbing fittings for fuel outlet and vent tube. As for the cap to fill the tank you can use smaller pvc fittings. A dremmel tool will come in handy for this part.
     
  5. taddthewadd

    taddthewadd New Member

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    I just re-read atombikes question about how to make the pvc tank and I realized I could do a better job of answering that so here goes...

    Yes figure out what capacity you want and use the size of tubing acording to desired capacity. Probably 3-4 inch would be good.

    Then you need to make three holes in the tube. One for vent, one for fuel line to carb. and a bigger one for the filler cap. The tubing is thick enough that you can use a tap to thread the holes. You would only need to tap and thread the vent line hole and fuel line hole. You can thread brass fittings in those two holes for the vent hose and fuel hose. I plan to use jb weld or something on the threads to help seal it since there wont' be a whole lot of threads due to the thickness of the pipe.

    Next you need to make the filler cap. I would cut a hole with a dremmel tool in the main pipe and glue a smaller diameter pipe for a neck (maybe 1" pipe) then you can put a threaded fitting on that pipe and use a threaded PVC cap for the gas cap.

    Finally gule on the two caps at either end of the main tube to seal off the tank.

    As for the vent line there are a couple of ways to keep gas from leaking out of it. One is a check valve which is a little plastic piece like a one way valve that lets air in the tank but won't let the gas out. You can buy this at a lawn mower shop. Or some people put a fuel filter in the vent line and the gas is absorbed by the filter and goes back in the tank.

    Hope this helps.
     
  6. K.i.p

    K.i.p New Member

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    Be advised there are two types of PVC, if you are going to drill and tap I would advise avoiding the "foam core" type. Foam core PVC is constructed with a smooth inner and outer surface sanwiching a lighter density core. I learned about this building a spud gun last year.
     

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  7. atombikes

    atombikes New Member

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    Excellent point that may not have been thought of otherwise!
     
  8. K.i.p

    K.i.p New Member

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    The volume of one gallon is 230.999952 cubic inches. Find the number of square inches of your desired diameter pipe (Pi x radius squared). Multiply this by the length of your tank to calculate total cubic inches. If you arive at 115 c.i. you have a 1/2 gallon capacity and so on. Good luck!
     
    #8 K.i.p, Feb 15, 2010
    Last edited: Feb 15, 2010
  9. taddthewadd

    taddthewadd New Member

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    I used to work in a hardware store and there were two types of PVC the "schedule 40" was thicker and could hold more pressure. This must be the one to use. Maybe the other PVC was the foam core you are talking about. Please correct me if I am wrong.
     
  10. TheE

    TheE New Member

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    If the pipe is meant for pressure, it will say "nsf-pw" on the side (North America). "nsf-dwv" is low-pressure (drainage) applications. "cellular core" means it'll explode if a kitten jumps on it.





    Ok, I'm exaggerating about that last one.
     
  11. K.i.p

    K.i.p New Member

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    tadd, the "cellular core" can be spotted easily from examining the end of the pipe, it will show three distinct bands of material, white, beige, white. I actually used the weaker foam core for the chamber on my spud gun but totally encapsulated it with the other fittings for safety. Although you are not working with pressure this idea would give you extra meat and strength for tapping and overall durability. Just some food for thought.
     
  12. taddthewadd

    taddthewadd New Member

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    Wanted to give you guys an update. I was at Lowe's today to buy some pvc to build the test tank. They don't sell anything larger than 3" but I ran into a guy in the aisle that said he had some scrap peices he would give me. So we met up and he gave me a 3' piece of 4" schedule 80! to those who don't know what schedule 80 means it is very thick. I would say the walls of the pvc pipe are at least 1/4" thick. I should have the tank built by friday. I will put gas in it and let it sit for a month then we will see how it held up.
     
  13. Retmachinist

    Retmachinist New Member

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    I have made a couple different PVC tanks. It will hold up to gasoline just fine. Just make sure you use the solid core it drills and taps very easy for your fittings. I used J.B. weld at the connections just in case the gasoline ate the PVC glue.

    John
     

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  14. bairdco

    bairdco a guy who makes cool bikes

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    if yer gonna gas it up and let it sit for a month, be sure it's got a vent, otherwise you might have a pvc pipe bomb.
     
  15. K.i.p

    K.i.p New Member

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    Interesting updates. Tadd, good to hear you got ahold of some schedule 80, that sounds like just the ticket. Score! Continued good luck.
     
  16. taddthewadd

    taddthewadd New Member

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    Retmachinist, What diameter is the PVC you used for that tank. It looks like it might be 4"? and is it shedule 40 or 80. Where did you buy it? They didn't carry 4" at Lowe's where I live. So I was wondering if you got it at a hardware store or a comercial type pipe company. Also that brass piece you used for the filler, is it threaded and glued into the pvc or just pressed in and glued? I know thats a lot of questions, whew.

    Here is another thing I will throw out there. The pvc the guy gave me is actually conduit pvc and is grey color. That shouldn't matter as far as holding up to the gasoline should it?
     
  17. Retmachinist

    Retmachinist New Member

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    That is 3" PVC I used on that tank. I bought a short piece at Home Depot. They sell it in 3' pieces as well as all the fittings. I tapped it for the pipe fittings, then sealed it with J.B.
    As far as the Gray PVC. I don't know if that would hold up to gasoline. That is basically used as conduit for wiring. I know from machining on it, it seems alot softer.

    John
     
  18. taddthewadd

    taddthewadd New Member

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    Now that you say it the grey pvc is softer. I will test it out by letting it sit with gas in it for a month or so. I hope it will work because that schedule 80 is so thick it allows more threads. In the meantime I am goint to build a 3" out of white pvc like yours.
     
  19. Dan

    Dan Staff
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    Been thinking about this for a couple of yrs. Very cool John, gave me the confidence in the material to try it
     
  20. bikebum1975

    bikebum1975 New Member

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    Very cool idea I like it may work for a bike I got that doesnt have a top tube I have been toying with dropping a motor kit onto.
     

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