I have an outdoor boiler and I have an electric hot water tank in my basement that was hooked up to the boiler for domestic hot water when the fire is going. It is just hooked up using natural convection to heat the water. It takes a long time to heat the water and this year I noticed that it gets cold after running out a couple of gallons. This morning I took a shower and about 5 minutes into it the water was luke warm on full hot. I made sure there was no air in the line last night. I don't know why this year it seems to be heating less water. I even turned up the mixing valve a little to get more hot water in the tank. Maybe I need to put a pump on that loop to push the hot water through faster? Any help would be great. Maybe I will take a pic of my set-up tonight and post up on here.