I am thinking about adding another hot water heater to one of my existing gas fired water heaters in order to provide more hot water and faster recovery. The current heater is 40 gals. Should I use another heater of the same size and should they be connected in series or parallel.
Maybe you should look into an instatanous hot water heater there are a few on the Market. The one I would reccomend is the Takagi TK1 They do have a web page at takagi-usa.com and you can purchase one thru comtec distributing @ 1-800-795-5925
The size is immaterial and they should be in series for several reasons, one of which is that you will never be able to pipe a parallel system so that the flow is equal in both tanks.