How to drain two washers

[searls03]

Hi, New here. I have plumbed before but never ran into this situation. I would like to add a second washing machine in our laundry room. Currently, the washing machine drains into a 2" standpipe, which then leads to a 2" drain line and finally to a 2" sewer stack (a secondary stack, not the main one). Can I simply add a second stand pipe and p trap to this 2" drain line (with proper venting of course), or would that over flow the system if both washers were to drain simultaneously? My other option (but not preferred if option 1 works), would be to add a second 2" drain line that the second washer connects to that will then lead to the 2" stack. Would that option work if option 1 does not? The 2" stack currently has a bathroom sink, kitchen sink, and the one washing machine hooked up to it.

Any advice or help would be great!

 

[John.g]

I have two washing machines with 18 ins stand pipes discharging into a total length of 7 feet of 1&1/4" ID pipe, I measured the flow rate years ago at 15 LPM/machine, and I reckon that this only needs a head of approx 1 inch in the stand pipes with the two machines discharging together. Assuming that you can allow a head of 12 ins of water in the stand pipes then 30 feet of 2 ins pipe should drain at a rate of ~ 120 LPM so that leaves you with ~ 90 LPM to play around with even with your two machines discharging together.

 

[rpm]

Are these washers domestic or commercial sized.

 

[John.g]

Both of mine are domestic.