Hi all:
I've got a tankless water heater which I love - as I tend to take extended showers sometimes and I love not worrying about when it will run out. I recently have upgraded my shower, however, to include multiple shower heads/body sprays, and now it appears the tankless doesn't have the GPM output to support the flow of these devices (the water is pretty much just a trickle when they are all on). I know there are at least two choices on how to solve this, neither of which I am particularly enamored with.
1) Add one or two more tankless water heaters in parallel in a manifold - this is extremely expensive 2) Replace the tankless with a large (e.g., 75 gallon) traditional water heater - I don't like this one since I may go back to running out of hot water, although it would clearly provide the flow I need.What I am wondering is about a third option - putting a 75 gallon water heater in series with the tankless - the 75 gallon being located after the tankless in the run. While I understand that once the 75 gallon is out of hot water the flow output would definitely be as low as the tankless puts out, what I don't know is what happens before that. Say the tankless puts out 5GPM while the pipes themselves (and the tank) can put out 50GPM. If I use this set up, does that mean I can get up to 50GPM until the tank runs out, and then the system will only be able to put out 5GPM, or will the rate limiting of the tankless limit the whole system throughout and the tank will only put out 5GPM even when it is full of hot water?