Drill the right size hole on the reservoir and push rubber grommet in; then, insert the pipe or connectors.
Be sure grommet's groove is fully inserted into the drilled hole.
If you have trouble with connection, please use soap or oil on the Barbed Elbow, Barbed Tee, Barbed Straight, Barbed Y Connector or PVC pipe to slide through drilled hole on the bucket or tank easier.