I had an addition added to my house. To accommodate the hot water demands in the addition including a hot tub. The plumber add a second hot water heater hooked up in a series. It work fine until I had to repalced the one they add that had a leak. Now I run out of hot water when I try to fill my Hot Tub. Why would this be?:confused:

Is it possible to isolate each heater... even though piped in series... some plumbers still pipe so can separate if wanted.. If can separate... separate and test each one for temperature/volume...

Are these gas or electric heaters.. Also, check the shutoffs... may be a bypass that is still closed from installation, etc, Let us know what you find.

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MASS gives some good ideas on what to check. I would not have installed them in series to start with. I would have done the new heater as a stand alone heater for the new addition and might have gone with a tankless heater since you won't be filling that whirlpool as pften as you may think. Until 1-1-08 you could get a $300 tax credit for a tankless heater, don't know about now.