Haven't seen a new trailer in years that did not have a set of bypass valves installed. Having said that I owned a 1977 Layton 220 for about 20 years that did not (at first anyway).
I found that if I added antifreeze to the fresh water tank, I would have antifreeze smell and taste for half the summer. Therefore I would disconnect the inlet water hose from the tank to the electric pump, and hose clamp on a length of hose (maybe 4') which would allow me to insert the other end into a jug of antifreeze.
Without a bypass kit, the hot water heater takes gallons of antifreeze to fill, but I would do that. Turn on the pump switch, then start at the farthest hot water tap from the water pump and run it until pure antifreeze is coming out. Turn it off. Do the same for the furthest cold water tap. Work your way back through the taps until you have pure antifreeze coming out each tap.
Pour a little antifreeze in each P trap under sinks and shower, and you are good to go. I would always buy -50 degree antifreeze in case a little water is still mixed in. You are good to go. I never had a problem in the past 42 yrs. of RV ownership.
You may still get a bit of antifreeze smell from the hot water for a while. If your unit definitely does not have a bypass kit, I would certainly have a dealer install one. It will save you gallons of antifreeze and a couple of weeks of that sickening sweet smell.
Harv & Deb
2015 Flagstaff 27RLWS
2010 Ram 2500 4x4 crew 5.7 Hemi, 3.73
Equalizer 1200 4 pt. Tekonsha controller