Plumbing codes are established on a statewide basis. County governments then adopt the state code in its’ entirety and then proceed to amend it to meet local conditions and needs. Cities and towns may also go through the same process with further amendments to the county adopted codes.

A Yahoo search for "maryland plumbing code" (include the quotation marks in the Yahoo search box) yields 107 results. If you do the same search, and are willing to spend a little time exploring, I’m sure that you will quickly find the information you seek. There are specific websites in the results for the city of Frederick, MD.

You might also want to contact your local Lowe’s store. Since they sell so many water heaters, they often have copies of codes that are specific to the local area available for their customers.

Good luck with your search.