scarf,
It all depends on approx how much your drain is pushing out what your recomended turnover rate is for the skimmer. Unless you have a fairly large skimmer and I'm assuming this is a needlewheel recirc, you will most likely need to tee off the drain with an adjusting vlalve to dial in the correct flow. Note that venturis, spray injection, becketts will not work since they need pressure rated flow, this is just good for a feed source such as in a recirc.
Sometimes, drain feeds are not cut out as great as they sound. Yes, they feed the most protein ladden water available to a skimmer but they also affect the skimmer performance due to bubbles and turbulence. If you have a durso, you will have air and water feeding into the skimmer.