Anyone out there on Wally World have an older but still operable Grundfos 15-42? Say from the mid to late 80's? I have a customer here in NH that has a Hydrotherm Celtic 50k input, that still works perfectly fine. Mfg date 3/1984. Some other contractor decided to replace the circulator. Instead of searching for the right one he installed a 26-99 in the frame that is built into the boiler...a newer 15-58/42 is too small. Now they are having air issues because the 26-99 is way oversized.