Just wanted to share my experience with my sidearm. I read where the plate exchanges are great but besides being very expensive they plug up if your water isn't pure. I have city water at my house and it's terrible so I knew it would plug, so I went with the sidearm. The one I got is 30inch long copper and nothing fancy. Around $40 and it's just 3/4 inside of 1 1/2. I just have it hooked up where my hot stove water ru a though it before it gets to my furnace. I don't have a addition circulator pump I just let nature take its course. Heat raises and forces the cool water down and causes a natural circulation in my water tank. Before I've read where the plate exchanges are instant and the sidearms work but are slow. I don't really agree with that. Now I did get a long side arm. They make pretty short ones so results may very with those. Within less than a hr my domestic hot water was extremely warm and has never had any issue keeping up. My wife has showered, then gave my daughter a bath, washed cloths and ran the dishwasher and right after that I took a shower and still had really hot water. Never had to wait for it to heat up. Also my pump is a 3 speed and I have it on the lowest speed and it still works great. I say this cause I assume the faster your water circulates the faster it'll heat your water. Could be wrong though. Anyways I'm glad I went with the sidearm exchanger. Lots cheaper, heats all the water in my tank and have never ran out of hot water yet.