I bought this tankless to replace a Paloma PTG-42PVN. The connectors, piping and size were all very close to the old tankless. I Couldn't be happier with the Eccotemp. So far its working perfectly. It has not failed once and I have yet to see an error code. My previous machcine, gave me error code after error code and would often shut off mid-shower. We suffered through this for years and Paloma was no help. A few tips about this machine that I could not find any info on when researching it. The top of this tankless needs to be connected to your Category III Stainless Steel exhaust piping via a universal 3 inch appliance adaptor. No special sizes needed, it just uses the standard female on both sides 3 inch adaptor. You cant find these in your local big box hardware store and it DOES NOT come with the water heater so Order it from an online retailer the same day you order this machine. You cant install it with out it. The water inlet and outlet are both 1/2 inch but they come with screw on adaptors that make them 3/4 inch. Be sure to use the supplied Rubber washer when installing the adaptor to avoid leaks. I tried to just use teflon tape but it was not enough. The Gas Inlet is 3/4 inch so make sure you use a 3/4 inch pipe to feed it gas. The big box hardware stores have a 24 inch flexible gas line designed for Tankless Water Heaters (7/8 external size - 3/4 internal size) that works perfectly for the last foot or two of the run. Dont skimp on the size of the gas line as Tankless water heaters need it. The Manual for the Eccoptemp says that the wall mounts adjusts but on my machine they were fixed. A few wood blocks were needed to space the machine far enough from the wall so that the exhaust pipes lined up, Overall view of this machine - Its a really nice product, especially for the price. It stands head and shoulders above the nightmare of a product that I suffered through with for years. When you first turn on this machine, you can see the temperature rise on the digital display to show the water temp increasing until it gets to your programed temp. If their is a gas supply issue, it just allows the temp to reduce a few degrees and then gets back up to temp when it can. My old machine popped an error code and then shut off. This machine is simple and easy to install, also its much quieter that my old unit. The manual that comes with the machine is a bit skimpy so if you need install tips, you can find videos on youtube on how to install a tankless that would apply to this machine as well.