Harold Kestenholz
It seems your tankless coil has experienced a plug. You can test the flow rate through the coil by putting cold water pressure in one side and seing the time it takes for 5 gallons to get out the other side. This is similar to the amount you will get out of the tap when the cold water to the mixing valve is shut off. If you have a clog, a professional can do a boilout or replace the coil as needed.
