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Tampering valve for older building
Working on an older building (10 units) and the dhw is supplied by a steam boiler coil. The mixed water temperature fluctuates all over the place, leading me to believe that the old tampering valve needs to be replaced. However, I spoke to a very helpful person at one of the tampering valve manufacturers and they said (as I understood it) that since the building has no hot water return piping and no recirculating pump, at times of no flow (i.e. no usage), the hot coil water (which can reach highs of 212) will heat the whole mixing valve and it will be ruined in a couple months. His suggestion was to possibly install a “fake” return line from the furthest point in basement that has a dhw line and install a pump on that line, with the purpose of creating flow through the mixing valve which will keep cold and tampered water at the mixing valve.
Any thoughts on the above? Many of these older buildings don’t have return lines or pumps on the dhw lines, what is traditionally done to keep water at 120 in these buildings?