Waste water from your cloths washer and kitchen sink SHOULD NOT drain onto the garage floor or into the backyard. This waste should discharge into an on-site septic tank or a municipal sewage system. Anything less is unsanitary.
We suggest that contact a reliable plumber (or sewer & drain service) in your area to make sure that the drainpipes are configured properly and draining freely. Thus, the best tool that we suggest you use is your telephone.