If it is under the floor and a MAIN pipe that can have a lot of water running through it then you should be fine. Just OPEN UP all the plumbing and let it flow flow flow. This is what I would do. I'd let it run on and on.
Stop the pressure on each device every now and then, then turn it back on. It will eventually wash.
Sure there are toxins, but honestly, there are toxins in our water anyway. I'd hesitate to drink until you've let the water 'rinse' for at least a couple hours at home, then a couple years of RV use/winterization. Then later, perhaps drinking would be fine (I would). But to each their own.