OP, if I were you I would just do two of the same seed side-by side, one with distilled, one without. And when you water from the tap, I would fill gallon jugs and leave the cap off for 48 hours to let chlorine evaporate (if your water system chlorinates the water, which it likely does if you don't have well water). All you need to do is measure the PH of your tap water once and you'll know what you're dealing with. If the PH is acceptable, then you're good to go.
My last grow I used distilled water for the seedlings, then switched to tap after a couple weeks. This time I'm just using tap, as it works fine.