u/Independent-Wish2037

I have a bathroom sink that drains to a sump in my basement. The bathroom was part of an addition that the previous owners had done that sits lower than the main house. Their solution was to have the bathroom drain to a sump which then goes into the septic tank. My question is do I really need a p-trap or can I just straight pipe it to the drain line with a flex pipe? I have replaced the vanity with a new one that is much larger so none of the pipe locations match and I am trying to avoid having to move them. What told I do?