When my on demand hot water heater was installed the supply line 3/4 inch was reduced to 1/2 inch ,the output of the heater is 1/2 inch and then is brought back to 3/4 inch to supply the house. Should I replace the 3.4 with 1/2 after the heater or will this be ok as is? I have to open the lines as there is an obstruction between the heater and the kitchen. What kind of loss can I expect in pressure with the present setup, 1/2 to 3/4. The present set up is 1/2 to 3/4 to a Tee from the tee to the laundry tub the other output goes to a tee and this feeds the bath and kitchen. Pressure is great at the laundry tub but both the bath and kitchen seen low. It may be because of a obstruction but if the line was clear with one valve on at a time shouldn't all locations be the same?