[Ann S]

I have purchased a condo and wish to install a stack washer/dryer. The drain lines are 1.5", and people have told me I need at least a 2" drain line to prevent overflow when the pump empties the machine. Is this always true, or is there any way to slow down the emptying so the line doesn't overflow? The drain goes through the condo beneath mine, and I can't replace it with a larger line. Thanks in advance for your help.

[speedball1]

people have told me I need at least a 2" drain line to prevent overflow when the pump empties the machine. Is this always true,

Not always Ann, but enough to give you concern. Today's more powerful washer pumps can overpower a 1 1/2" trap and drain. I know. I have the same problem. Let me tell you how I solved it without the expense and hassle 0f replacing with bigger piping. I installed a ( see image)compression fitting,( you can do the same thing with duct tape and rags but the fitting's better). This makes the discharge from the washer hose into the stand pipe a closed system. It makes it impossible for the washer to overflow. I've had this on my washer for years with no problems and in all the times we have recommended to people like yourself we have never got a complaint about back ups or a problem with the pump. Good luck, Tom

[Milo Dolezal]

Tom is giving you excellent advise. As he said, you have a good chance that it will work just fine w/o overflowing...