I am still working on the sparging setup. I have moved from a comum made of PVC to a hot water urn, and now to a stainless keg. Last night I thought I had everything ready for a first batch using the urn. The setup was working well with water, with no impurities in the water after a few runs. I cleaned everything then added a small amount of peroxide to the urn which started fizing immediately from one section of the heating element (while it was off). I think that the element must be braised with something containing a incompatible material (silver?). I also found out that the heating element was not stainless but copper coated in stainless when a bit of the coating flaked off. I am running some tests with a 19L keg now. The heating always a issue. At the moment I am heating the sparging air with a air conditioning condenser in the urn, as well as the keg with another electric heater. One thing I learnt from the PVC tube is that you want the number of things in contact with the peroxide to be kept to a minimum, so you really need to heat from the outside. I am thinking of immersing the keg in a water bath but that seems a little messy. Heating the air is a more elegant solution but even with the air piping hot it barely warms the solution, and it takes quite a while to heat up.
I plan to do a compatability test with the keg wendesday and if everything goes well I will line the clean area with plastic and concentrate the first batch. I would like to set everything up so that I don't have to transfer any peroxide between vessels myself while sparging. The great thing about using a keg is that it is concentrated in the same vessel it will be stored in. I haven't figured out how I will transfer the peroxide out of the keg for use. It has two connections on it, one for liquid out (has a tube going to the bottom of the vessel) and one for gas in. I will probably have a small hand pump to pump air in to the keg once I close the lid which will push liquid out of the liquid fitting. Usually carbon dioxide is pumped into the vessel from a cylinder.