there is a check valve in the drain assembly so you will be fine without it, its just if there is something that gets caught in the check valve to hold it open that will be an issue, you could pull the hose off the back of the drain plug fitting and double the hose over and put a zip tie over it and tighten it to pinch it off if you are worried, the drain plugs don't have a very good retention on them, its only the last couple of years since they changed them from the old style they had for years that they have been a problem so nothing related to just the spark. I just make sure they are always screwed in, and the only time I take them out is when they sit at home, I always put them back in before hitting the road.