I bought a house that has a 3 ton geothermal heat pump configured with an open loop. I want to convert it to a closed loop. I was researching and asked some questions on here in 2015, with the intention of performing that work in 2016. Other responsibilities got in the way, and now I am back reviewing my notes along with threads from this forum and the questions I had asked. I hope to do the conversion in 2017. Back in 2015, I was thinking series horizontal loop with propylene glycol, I was corrected am now on to considering parallel horizontal loop with methanol. Also, early on I had found some used butt fusion equipment but that purchase did not work out, so now I am going to go with socket fusion. So the following questions regard flushing and purging: I knew that with butt fusion, the fused pipe seams are narrower than the internal diameter of the manufactured pipe. When PE pipe is socket fused, are there pockets inside the weld between the two pipe pieces that could trap air/dirt during the flushing/purging? Should flushing/purging be performed before or after adding the methanol? What sort of filter should be connected to the flush cart? I was thinking of a whole house filter from one of the big box retailers.