I'm assuming your checking your tanks underwater with pressure in them. A simple 5 oz. syringe will do this just fine assuming you have the other caps properly terminated. Old tanks with the plating oxidized and surface rust on the outside needs to be properly dealt with prior to soldering. I scarify with a soft bristle wire wheel in a drill press followed with a cleaning of lacquer thinner or acetone prior to soldering. Unfortunately though, a locked seam that's rolled will not allow for a proper cleaning therefore a more thorough treatment of the wire wheel may be necessary to clean the joint to accept solder. Proper temp and cleaning is imperative. I'm quite handy at soldering and while there are those that mention they use a very low wattage iron, I use a very high one. Tank caps once soldered onto the tank can quickly get heat soaked by the rest of the tank. This is why having more than enough heat is important. This is generally not an issue when installing but more of one when taking apart. Tank caps will retain a bit of solder where the initial contact was made leaving that area already tinned. Many times as the solder cools it forms a radius which until properly heated doesn't allow the end cap to properly fit. I either wire wheel this solder out of the joint or remove it as best as possible leveling the solder with a pencil iron.
Prior to assembly, I use a wood dowel and rub it inside the tank to spring out the metal slightly and remove any oil canning or dents. Bending the end cap by placing it onto the tank and using a small hammer can tighten up the end caps allowing for a nice fitting cap which assists in the soldering. This prevents any fish mouths caused by the tank not fitting the end cap properly. Solder doesn't bridge large gaps well and are subject to vibrations which while it may pass your pressure test, it can also fail when in use. Older tanks however used a lot of brass tubing which I have found to split internally causing problems which a pressure test won't reveal. Replace the pickup tube with quality copper K&S tubing and insure that you solder it to the rear of the tank. I have never come across a Perfect tank that had it's pick up tube soldered inside. As I mentioned about the brass, the Perfect tanks utilized brass for their tanks. Having flux on your hands and touching the parts can also cause oxidation. Keep the tin as clean as possible. Solder your front cap on and pickup internally, including your fill and vent pipes. Next wash the tank thoroughly using a acid brush with thinner or acetone removing all traces of flux and other contaminants.
Soldering the rear end cap on next, I try to place the cap on tightly as mentioned above and I run a small bead of flux around the perimeter of the cap. I use very little as I don't want to introduce flux into the tank. I solder the end cap on with the last cap facing upwards using the heat to draw the solder into the joint. I then fill the tank with a high castor based fuel and let sit overnight. . I make certain that for the first few runs I'm using a inline filter. This takes a bit of time usually around 2 hours to do this but I rarely have a issue afterwards. It allows me to properly clean internally and solder all joints correctly. I have found issues with almost all commercially available tanks from pipes falling out and leaking to pickup tubes not being soldered correctly to not even being in the correct location.
I have a Mighty Vac which I found due to having so many inline connections can show more leaks through the connections themselves opposed to what I'm actually testing. The underwater method works fast and shows immediate results. Prior to me placing the tank underwater, keep in mind that flux can mask a small pin hole leak so cleaning the joint first is also important. Try and inflate the tank as though your trying to pop it.
Topic: metal tank repairs/mods (Read 2169 times)