heater hose bypass

[kglowacky]

I read somewhere that it is not a good idea to install a manual block valve on the heater hose going into the heater core without installing a cross over tee
connecting the input and return heater hose from the heater core. it is needed to keep the coolant flowing as a LS motor needs the coolant to always flow. Anyone know if this is correct. I am running a all oem setup except for the compressor. Thanks