I pulled the check valve out of my forward head because it was back flowing back into to bowl,I cleaned it the best that I could and put it back on the lines ( I tried to buy a new one but being it's a Beneteau you can't just walk into west marine and get a new one,so I gotta order a new one from Beneteau ) getting back to my issue,the water won't go down the pipes when I flushed ,what'd I do wrong hopefully someone can help with this issue...