Wonky heating supply/return lines

[Tim McCahill]

Hi all - I own a four-story apartment building. At some point, probably when the building was turned from a single-family to a multi-family and the utilities were separated, new supply and return lines were run from the boilers in the basement to baseboard heaters in the apartments. These lines zigzag and turn up or down at sharp angles; not one has a straight run up or across. Related or not, the system is always full of air - I purge the boilers weekly and within a couple of hours the pipes and fintubes are running noisy. I would like to update the system and would benefit from any insights or experience the community has replacing or improving an old or efficient heating system. Many thanks!

[Tom W.]

Tim McCahill
Check the water pressure on your boiler. The standard setting of the pressure reducing feed valve, when the water is cold, is 12 psi. With a 4 story building this pressure setting is not enough to overcome the weight of the 4 story water column in the piping. The pressure will rise as the boiler heats because the water expands but as it cools and the volume of water contracts, it will actually create a vacuum in the piping on the upper floor, causing air to be drawn in through automatic air bleeders. You will need to increase the standing pressure on the boiler at the least. In addition you may need to upgrade the expansion tank to accommodate the extra volume of water.