Washing Machine Drain Sizing.

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    • #279547
      MasterPlumbers
      Keymaster

      I am remodeling the basement bathroom and laundry room in my 1940’s era house. I would like to move the washer, but am unsure if the drain line available will be able to handle the washing machine drainage. Here are my concerns…
      Originally the washing machine was in a spot (we’ll call it position one) where the supply lines came from the wall and the drain dumped directly onto the adjacent shower floor. At some point the washer was moved to from position one to position two and new supply lines were routed and it drained into a utility sink.
      I would like to move the washer back to position one, but will not be able to move the utility sink. I do not want to dump the water onto the shower floor as it will be beautified (it was just cinder block and concrete). I have the ability to drain the washer to a nearby 1-1/2″ drain line.

      Now my washer installation guide says that if I have access to a 1″ line I can buy a 2″ to 1″ reducer and use the 1″ line. Based on that I am comfortable using a 1.5″ drain line, however it seams like most people use 2″.
      I’ve tried to find pipe sizing charts online and was able to find a pipe sizing calculator that recommended 1″ pipe for my washer’s required 17 gal/min (64 L/min).

      Can anyone confirm if a 1.5″ pipe will be able to carry away 17 gal/min from a washing machine?

    • #301154
      CincinnatiPlumbing

      Washing machines can either be drained into a laundry tub which has at least 1-1/2″ drain or into a 2″ stand pipe. The reason for the the difference in sizes is that the laundry tub can hold quite a few gallons of excess water while draining.

      Here in Ohio, we are additionally required to have the 2″ standpipe and trap dump into a 3″ stack or horizontal branch.

      17gpm is quite a bit of water.

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