I developed a water leak where the water pipe.

I developed a water leak where the water pipe goes into the engine block. I remove it and bought new o rings. Easy peasy so far. Came to put the pipe back in and just couldn't get all the o ring in - kept bulging out. Is there a trick to this or am I doing something wrong. I've oiled it, tapped it, squeezed it, sworn at it but still managed to destroy 2 o rings.