I'm attempting to relocate my washing machine and dryer to my garage. Technically I will be building out a portion of the garage so it will be climate controlled. I can handle the hot and cold water lines but I'm concerned about the drain. My neighbor was a general contractor and he thinks the easiest way to rough in a new drain is to go through the exterior wall and then tie into the cleanout for the kithcen sink. The kitchen sink is on an exterior wall and the washer's new location would be on an exterior wall 5 ft fromt the cleanout on the kitchen sink. I live in a 1950's house on a slab. It appears that I have a standpipe as a drain now. Is it necessary for the drain to be vented through the roof? Also, does running the drain into the cleanout of another pipe, (basically extending the cleanout) make sense? Is that the only way to do this without busting up my foundation?
My neighbor said we would just need to put in a planter to cover up the pipe and protect it from freezing. Any help would be appreciated. Tom, if you are answering, I read your tips and I'm glad you are getting better.

Unless you live down south that's going to need to be a very big planter to prevent freezing. The vent should go through the roof, do not connect to the litchen drain unless you can confirm that the drain is at least 2", anything less than 2" is not enough for a washer.

Memphis, Tn. I didn't figure I would have a problem with freezing since there won't ever be water sitting in the line. It would always be empty except when the washer was emptying. Am I missing something?

So standpipes are always vented? I figured that was the purpose of having the pipe bigger than the hose. Just clarifying.