In design stage of new 28x40 detached garage. I am in the country, so can drain to daylight. Plan on washing cars in garage. No heavy/mud covered construction vehicles. I am in Iowa, so freezing at end of drain pipe a concern in the winter. Space will be kept above freezing year around. Existing attached garage has an approx. 15’x1’x1’ trough with 3” dwv pipe to daylight, with custom made grate. Trough is concrete, formed and poured at same time floor was poured. Drain pipe is flush with bottom of trough, with female threaded fitting on bottom of trough. When I wash a car in the winter, I plug pipe with threaded plug. Trough is big enough to hold the wash waste water, reach in and pull the plug when done so water rushes out and does not freeze. Leave plug in day to day in winter to catch snow melt from cars. This works good, however, wondering what others have done. Home use, no commercial activity.
