Hi all I'm new to the forum and hope I can get some good advice for questions I have about properly setting up an exit water discharge manifold for an open loop system. I have spoken to many local installers and have received disparate and unclear advice. I have a Water Furnace, model ATV045D110CRT (installed in 1994) and, according to the manual, this unit should flow from 3-6 GPM on stage 1 and 6-9 GPM on stage 1 & 2 together. Currently, I have a square-shaped manifold made of PVC connected to the furnace discharge fitting where the water enters a tee, flows left through a solenoid valve for stage 1, and flows right into a second valve when stage 2 fires up. One big issue I have right now is a significant water hammer that occurs when the furnace shuts down or when stage 2 reverts to stage 1. I know this is from my use of standard, fast closing solenoid valves--these need to be replaced. So, with this background, here are my questions: 1. What would be a good, solid slow-closing solenoid valve to replace mine? My web research has led me to the Taco 5101-G2--they seem to be commonly used and effective. Am I on the right track here? 2. I noticed that the 5101-G2 has a flow rate of 4.5-6 GPM. Does anyone know what this really means? Does the valve somehow control the amount of flow going through, or am I missing something here. I'm thinking that having two of these for my system would allow enough flow for stage 1 alone and for stage 1 & 2 together. 3. I've been told that I probably want to install some flow-restrictors or "circuit-setters" or "ball valve regulators" to control the flow going through my system. Would you agree? If so, could you provide some recommendations on what, exactly, I should buy and where they would be installed in the plumbing? For example, up or downstream of the solenoid valves? 4. I've also been told that a flow meter would be useful--but the same questions apply here. What, exactly, would be a good product to buy? Where would it be installed? I'm assuming that the reasoning behind being able to control your flow is because you don't want to waste energy from your well pump. So, for my system, I assume it would be set for the minimum flow required for stage 1 that still prevents freeze-up, and the same would hold for stage 2. To be safe, I could set stage 1 for 6 GPM (which is the max flow of the Taco valve) and set stage 2 for an additional 3 GPM. Does this make sense, or am I missing something? Would you need a separate flow meter for each line? 5. Finally, I've read that installing a pressure reducer on the line going to your furnace is a good idea. Right now, the water line going to my furnace is at household pressure--about 60 PSI. Comments or advice on this? I know this is a lot and I apologize if these topics have been covered in part elsewhere. I hope to get solid advice on my entire discharge system so I can take action soon. This water hammer is making me very nervous. Thanks all Cheers Matt PS--any reason why you couldn't make your manifold out of PEX?