I had a pair of Weil McLain high efficiency boilers installed in my building in August 2006. The boiler control isn't operating them properly, and my plumbing contractor thinks the problem is that the boiler outlet temperature sensor is strapped to the OD of the pipe rather than being in a well. The piping is put together with groove end pipe and Anvil Gruvlok Rigidlok 7401 couplings that are 1 7/8 inches wide. I'm wanting to take out one of these 7401 couplings, and put in a Victaulic outlet coupling that's 2 3/4 inches wide: http://www.victaulic.com/docs/lit/06.10.pdf That means I'm going to have to also replace one groove end pipe with a shorter pipe as well simply because the wider outlet coupling will require the groove to be in a different location. I've been told that the standare specification for groove end pipe is a 1/4 inch groove located 5/8 inch from the end of the pipe. Is this true of ALL groove end pipes, or only for 2 1/2 inch mild steel pipe? Does anyone know where I could find that specification so that I can confirm for myself? And, how strong are the seals that fit in those grooves? If I get the location of the groove wrong by 1/8 inch, will the seal be strong enough to hold the piping in place if it's wanting to spread apart or come together? All the piping is hanging from pipe hangers and it's about 12 feet between where the ends of the pipes come out of the walls.