| I have started and stopped answering this question about 3 times now. Even finished the answer twice. :-) This is the rubber meets the road kind of problem. So no its potency isn't changed since the oil doesn't disolve into water. It will be carried or moved away by water if there is sufficient force to overcome the oils surface tension which binds it together and other things like dirt. It is still as potent and still urushiol just broken up into smaller oil droplets if this makes any sense. It may be there or not. All depends on the flow and pressure of water. The soap page discusses how to do this with less pressure.
Here is the realty that I observe. Yes it sure does seem to effect it potency because after a good rain there isn't much left that hasn't been carried somewhere else (ie. into the soil, to the neighbors yard, the sewer, etc). I have walked with my dog in many rain storms and he has been in poison ivy. I just dry him off and wash my hands as you do with soap and water and no problems. That doesn't mean we got it all as who can tell. But if there is any left... I didn't touch it and I havn't received any rash. :)
I think you are probably ok if everything is soaking wet. Thats the rubber meets the road part of this. Technically, we have to say well I supose there can be some oil left. But you have observed like I do that if there is any break outs it is greatly reduced. Great question. Still not happy with the answer.
Anyone else with a thought on this? | 
