Two Line Fuel Tank vs. Three Line Fuel Tank, What are the Pro's and Con's to each

I'm debating which system to use in a current build. The engine compartment will be kind of tight in regards to accessing the the fuel line going to the carburator, so I'm thinking a three line system will be easier to fuel/defuel. The problem is, I've never used a three line system and don't know if there are any con's.

I'm asking for your experienced feedback here .

This post has been edited by TJR on Dec 18 2010, 01:26 PM

I've seen it both ways.. I like to keep it simple with 2 lines

I would generally agree with you Jon, but in this case, trying to reach the fuel line going to the carb may not be so easy, even with hemostats. That's why I'm considering the three line system.

Then the simplest way may be a 3rd line. Normally I just run a T on the clunk line with a plug..

A "T" in the carb line wasn't something I thought of , but it would seem to me to offer too many week points. By the fact that it's a "T", there are three points of possible failure (potential air leaks). A third line would only offer one point of failure, that being where it's plugged.

There are other type of fuelers as well. I don't like running 2 clunk lines as you have an extra line to interfere with the clunk line, an extra line to rot etc.. But that's just personal choice so.

Usually 3-line systems are a pain and totally unnecessary...
But in your case it may be the only way...

I prefer to use fuel dots... They are simple and look neat and clean...
Use in tight situations or cowled installations.

Exactly, the dots are what I use all of the time.. I like the H9 dots but a dot is a dot is a dot

This post has been edited by jonkoppisch on Dec 18 2010, 05:42 PM

Unless they're DOTS.

http://upload.wikimedia.org/wikipedia/en/3/33/DotsCandy.jpeg

I wouldn't put that past some people to try (mmmmm avist......)

Frits, every point where fuel tubing attaches to the "T" is a possible problem area. I realize that it's highly unlikely to ever be an issue, but why chance it.

http://img72.imageshack.us/i/fueldot2.jpg/

This post has been edited by TJR on Dec 18 2010, 06:05 PM

I use a Kwik-Fill Fueling Valve

http://www.shopatron.com/products/productd...r=334/101.0.1.1

For the third line just used to fill and empty the tank, you could use a brass tube inside the tank, sort of like the vent line, but turned to bottom of tank.

I have a tee and fuel dot on one of my aircraft. The only problem has been when fueling, a small amount fuel spills through the carberator and when draining, a small amount of air is sucked out with fuel causing more time needed to drain. No problems with operation or starting of the engine which is mounted on its side.

Im with you Andy.

Thats what I use as well Andy.

They were the rage in my first few years of flying, and I had several.
But the o-ring in them can start drying out and leaking after a while, and then you have problems with air leakage. They do look nice.

As far as tubing connections leaking — I have never had those plastic tees leak if they are properly sized.

Connections usually fail where silicone tubing connects to rigid metal tubing:
• Inside the tank where the clunk line attaches (tubing movement.)
• Inside the tank compartment, where the tubing connects to the brass or aluminum tubing (sharp edges, vibration.)
• At the carburetor (vibration.)

I agree with Frits! + sometimes with using that kind the insert wont come back and center properly and leak air once again..

The one on my 40 size cub has been on there for about 4 years and have not had the first problem.not saying I won't but so far so good.