You can contact the town of Manor's building department to determine if the plans are there as the plumber may have had a permit for the addition.
It's possible that the name of the plumber is on file there who performed the work so that you can contact him about the drawings if the building dept doesn't have them.
One would hope that you would be able to find this specific information since it's only an eleven year old home. Consider contacting the builder. They should have a copy of the building plans on file. It may cost you a little money but having access to these documents may save you money both now and in the future.
It's likely you will not find any already done. Many homes are framed and the plumbers go in and do their work as they go with no plans at all. I am not sure why you want them, but you are likely going to have to hire a plumber to try and figure out what's where.