Last week I found a problem with my launcher.  When I tried to launch my first rocket, the pressure was not strong enough, even though all my calculations showed that it should have been.  Then I found out wh it wasnt working.  It was because my non return valve (The valve that keeps the pressure from returning) was not sealed completely.  I was not sure how to fix this, but today, I figured out how to do so.   By using a mixture of apoxy glue it should be able to keep the valve sealed.