Are Diuretics helpful with eliminating fluid thru tummy tuck drain?

Unfortunately directors not help you reduce. You must trust your plastic surgeon's judgment. If you have a persistent seroma you may need to have slightly tighter compression or a sclerosing agent placed to help decrease the seroma formation. 

Diuretics will not help.  They will increase your urine output, but will not do anything for the drainage.  The drainage is quite high.  Please consult your surgeon or obtain a second opinion about your situation.

I am sorry to hear about the trouble you are experiencing with the drain output. I would share your concerns about removing the drains too soon;  in my practice, I would leave the drains in place until their output is significantly lower. The risk of infection taken by leaving the drains in for longer period of time is relatively small, compared to the risk of seroma ( fluid accumulation). I would not suggest the use of diuretics;  their effectiveness in this situation is unknown. On the other hand, the use of diuretics may result in problems with fluid shifts (possible dehydration) and/or electrolyte imbalances. Best wishes; hopefully, the drain output will be decrease significantly over the course of the next one to 2 weeks, without additional intervention.