Reader Elise is having problems with her new tankless water heater:
We purchased a tankless a few months ago and have had ongoing problems with low water pressure. The plumber says it is our well, but we had no problems previously, with the exception of running out of hot water, which is why we got the tankless. Every time we flush a toilet, we have no pressure and no cold water in the house.
Some sources: Plumber Terry Love maintains an excellent website and forums. You might find answers on the shower and bathtub forum. GardenWeb also has a lively forum posting on tankless water heaters.
If you have some insight into this, please post below.