Can I use 2 different sizes of heater hose?

[adioteque]

I'm rerouting my coolant line under my bus and currently the system is using 1" but I would like to mend in 3/4 for the two 30ft runs under the bus.

Would this cause pressure issues or cause air bubbles?

 

[Jolly Roger bus 223]

do you have a pump to move the coolant?
either way i dont think it would cause to much issue other that your heater wont get as much flow as it used to.
example 1" pipe carries 12 gpm and 3/4" pipe carries 9 gpm.
notice i said example because there are variables that factor in for specific fluid,pressure and bends ,turns, heater connections, heater core itself but at a minimum in a perfect world your heater will not be as efficient as it was.

 

[adioteque]

do you have a pump to move the coolant?
either way i dont think it would cause to much issue other that your heater wont get as much flow as it used to.
example 1" pipe carries 12 gpm and 3/4" pipe carries 9 gpm.
notice i said example because there are variables that factor in for specific fluid,pressure and bends ,turns, heater connections, heater core itself but at a minimum in a perfect world your heater will not be as efficient as it was.

The hope is that a lessened flow would not be an issue because less parts are being serviced but then again those heaters were dispelling heat, even off. so the coolant would theoretically be hotter.