This is an old entry that wasn't finished. I went ahead and finished it so you can see how I did my tanks.
The tanks are welded up and at my house now. Before the tanks were being welded I ordered some flush bungs so I could have the shop weld those in. The bungs are threaded disks that get welded onto the tank that allows me to thread valves and such to the tank. Well they where on back order without my knowledge. After a week of waiting I made the decision to have the shop weld iron couplings on to the tank instead of the bungs. I did try calling the "bung" company and emailing them but I could not get a response.....so much for customer service. The bungs showed up about a week after I took the tanks home. I tried calling again and was able to speak to a person who said I could return them for a refund. I'm a little leery of doing that...I'll be out the bungs and the money. (Update - the company refunded my money! Yeah!)
First things first...I need to test the tanks for leaks. The leaks are where you see bubbles.
Yup I found a few. But no worries I have a mig welder and can weld!
I leak tested them and found a few leaks.
I re-welded the tanks where the leaks where. I then ground down all the welds a bit to knock off the high spots. Then I tested for leaks again and found none. The way I test for leaks is to plug all the openings except two. One of the opening gets a pressure gauge that reads lower pressure. The other gets a valve that I can pump air into with a compressor. I only put 3-5 psi in the tanks then spray them with a water /soap solution on all the fittings, seams and welds. I look for bubbles and that tells me where I have a leak. Once I get all the leaks fixed I pump the tank up to 3-5psi of air and wait 24 hours to see if the pressure has leaked down any. If not then it is good to go.
24 hours later....
The pressure held so the tanks are good to install. Before I can install them I have decided to paint them bright red to pretty them up. I had dressed the welds up before I tested them but they were still a little less than perfect looking. I used some long strand fiberglass on all the welds and faired it in with the tank body. (I took a year and a half of auto body classes a few years ago.) I then sanded everything smooth, primed the tanks then painted them with red rustoleum paint. I put two coats or primer and three coats of paint.
For the pick up tubes I could not find anything that I liked so I decided to make my own. I used 1/4" soft copper tubing and soldered it into a reducing nipple. I created a flare on the copper so it would fit snug in the nipple. I then soldered it in on both sides of the nipple. On the end in the tank I cut a bevel and made the tube so it would be about a 1/2" above the bottom of the tank.
Just a note...I did put a bung in the bottom of the tank with a valve. I did this for two reasons. First I figured if and when I get water in my tanks I can drain them. Second if for some reason the pick up tubes failed I could feed the engine from the bottom valve. I also put a plug in the valve in case the valve was accidently opened.