I am planning on completing the installation of the second (sucker) pump. I am still unclear as to what physcially happens inside the loop with the one circulator pump pumping away from the heat source. Is the water returning back through the monoflow T or is the flow just running out of steam. It seams that if it just a flow being reduced to 0, then the water inside the heater still at the full rate of volume maintained from the cold supply from the town, should begin reheating. I have not found that to be the case. The return water comes back through all the piping lukewarm while the hot water just before the pump is still hot and after about 30 minutes, everything is ice cold, almost as though the water stops circulating. However that cannot be, if the pump is no longer capable of circulating the water, then the water in the tank should get hot after an hour. I understand there are some flaws to the setup but before I can start adding more modifications, I need to assure that there isn’t something preventing the water from running through the piping and being brought back in through the monflow. There must be a huge volume of air that is creating some kind of blockage in the line after the pump is run for a while. I could always hook up 2 more pumps to the manifolds before and after the loop on the pex tubing in the floor. Harold I emailed a few pictures to you to see the layout and the manifolds on the slab.