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If the brass tubing is splitting, the brass is not annealed.

Having replaced a couple dozen drain tubes now, I have learned the importance of annealing the brass correctly. You need to heat the brass to a high enough temperature that actually anneals the brass while at the same time minimizing the heat transfer down the tubing which can lead to internal buckling of the tubing during the flaring process.

While it is true you do not need to heat the brass until it is glowing red, you will be safer if you get it very close. Initially I was heating the tubing until it turned a bluish color and then quenching it but I sometimes had trouble with it not being soft enough.

I now try to heat the end of the rube until it *just begins* to turn red, then stop. I also minimize the heat transfer by holding the tubing with a soaked towel which acts as a heat sink to limit the annealing to the very end where the flaring will occur. Hold the torch tip so it points slightly away from the end of the tubing instead of pointed down it; that helps too.

Some more bits of advice (that I have offered before but are worth repeating): Buy extra tubing. It is perfectly reasonable to expect a mistake or two. Brass tubing is cheap and you should really have some extra on hand in case you mess up.

Remember, do your longest tubes first so if you do mess up, you can recycle the tube on another, shorter location.

If you are ordering some tubing from McMaster-Carr and need three feet, order six feet. But do NOT order a six foot length, order two thee foot lengths. The shipping for one, or two, three footers is about the same but a single six footer is MUCH more expensive to ship.