Im having problems trying to get the two side tanks to pull equally. Sometimes they will pull within a few gallons and sometimes they will pull almost 2 to 1 from one tank. I’m thinking there maybe some trash in one tank obstructing the pick up tube. Then sometimes when the pump isnt engaged it falls back into the tank. Does this sound reasonable? I have two lines running to a brass T fitting, from there it runs through an inline filter to an electric pump. It used to have a mechanical pump but I put in an electrical pump chasing a fuel pressure issue, which ended up being trash caught in the T fitting. I put in lines on each tank but noticed the tanks not pulling the same. At the time I thought the issue was the filters not flowing the same and went to a single in line after the fitting. A friend of mine has side tanks with them tied together at the bottom but I?ve heard this is illegal. Any thoughts on the issue or advice on how to get them to pull equally would be greatly appreciated.

Just to confirm, we are talking a single engine boat, correct?

1) Are both lines from the tanks to the Tee connection the EXACT same length?
2) Are you certain that the vents on both tanks are completely clear?

The pump is going to draw from the path of least resistance. Both of those two above factors could be hindrances.

Yes it's a single engine boat, the hoses are cut to the same length.

As far as venting goes it vents through the gas cap, would it make sense one cap could just be tighter then the other?

Potentially, yes; that's where your variable could be.
As delicate as this 'situation' is; perhaps it would be best to have separate open vents pulled off the fuel fill lines.

This is the vent we install on the Active Thunders:
http://www.nauticexpo.com/prod/roca-...06-260069.html

I have 2 tanks one on each side. Both tanks are vented directly in the top . Hoses are the same length. I have the same problem you do. What I did was make a Y fitting and put ball fittings in the top to regulate the level in the tanks.

Ayuh,..... Get Rid of the "T" fittin', 'n install a tank selector valve,....

Due to the nature of liquids, you'll never get the tanks to draw down evenly,...

Eventually, you'll run Outa gas, when 1 tank goes Empty, 'n there's no way to draw outa the tank with fuel in it,...