"Over-top-filling" of tankers is not as popular any more as it once was. Most tankers today have some type of direct fill line located on the rear of the vehicle that goes directly into the bottom of the tank. On older units with non-existent direct tank fills or "too small" of a direct tank, outfitting the rig with an over-the-top fill might be a more economical choice than trying to retrofit a larger fill pipe through the tank.

A quick way to fabricate a reasonable over-the-top fill pipe is to use 4-inch pipe and have the discharge end dump into the fill tower on the tank. The inlet end can be trimmed out however you wish: a check valve can be used if needed - or in some cases - folks use no control valve.

Note: In general, an over-the-top fill pipe is not faster than a "through-the-bottom" fill pipe of the same size because both have to overcome the head pressure of the fluid that they are moving -one has to overcome it in the tank and the other one overcomes it in the pipe.