We have a second floor laundry room which is next to the master bathroom. When the shower is turned on and toe tester being used, nothing comes out of laundry room drain. Once the knob is pulled and shower starts, a slight bubble/spray comes up laundry room drain. After a normal shower, there is a tiny bit of water around the drain (not enough to run away anywhere) but a little bit of spray on lower part of dryer. This seems very weird as the house is brand new. When I take the chrome cap off the laundry drain, I hear water running so obviously master shower is connected to laundry drain but the spray only happens when shower is on and not when toe tester is running

Any advice would be appreciated.

Thank you

could be a venting problem ??

Is the "laundry drain" a floor drain? In any case, there should be a trap for the drain and you shouldn't hear water flowing. Is there a warranty on this house?