Making seams waterproof? Sewing Machines Parts and Sales in Los Angeles

I’m making some bags out of PUL. The bags are intended to hold used cloth diapers and will need to be washed regularly. I would like to make the seams waterproof as well but I cant seem to find a lot of information about sealing seams and how machine-washable those seams are. Anyone have any information they can share to help me out?