I have built a new shop and put pex in the floor for heat. 600sqft. with 600 ft. of 1/2 tube. I was told that I could use a hot water heater for boiler and use as hot water for sink. Now I find out that is not the best thing to do, so I have the wrong pex in the floor, was told that is OK use all brass or copper and that is OK. That is what I will do. Now know one will help me make up a sys. I want to use a Takagi jr. heater,I thank all I need with this is are Sprovent jr. air eliminator valve, Expansion tank [2gal],1/25hp bronze pump, back flow preventer, pump relay for stat,T&P relief. I have read all I can Find on this stuff I have done a lot of plumbing and remolding and I think I can do this if someone will give me some answers.