Should I replace recirc pump for my tankless heater?
I recently bought a house which has a tankless heater, and is coupled with a recirc pump which isn't working. The system does have a dedicated water line for the recirc pump. Unfortunately the designer of the house put the water heater at absolutely the opposite end of the house from where all the water is used, and consequently it takes 1-2 minutes of running the water before hot water shows up when the pump isn't working. I have a few questions about it:
1) If I replace the pump, how fast will hot water get to the outlets? It seems like theoretically it could be almost instant, is that right?
2) With a pump in operation, is there a risk of having the water go warm/cold/hot, or are temperature fluctuations few/gradual?
3) Isn't the whole purpose of an "on demand" water heater nullified by using a recirc pump, or is it actually still more efficient than a tank heater?
4) How hard is it to swap out a broken pump... I've done a little bit of soldering etc. before, but am no plumber, that's for sure.
In case you're wondering, my tankless is a Noritz N-084M-DV and my recirc pump is a Laing Ultracirc UCT-909.
Thanks in advance!