I have low pressure steam heat in a 3 story house. Whenever the thermostat cuts the boiler off all the air vents suck in air for a minute or two. Why am I getting negative pressure so quickly?

I’m planning to insulate the pipes in the basement to help matters but I have lived in other buildings with all exposed basement and riser pipes and they still had lots of pressure throughout. Any ideas?


Comments

  1. I never checked the pitch because the pipes looked pitched but it turned out to be an optical illusion because of a nearby drain pipe pitched in the other direction. Put the level up and the water was obviously going nowhere for 20 feet. Fixed one side of the basement and the heat came in faster for sure. Need to do more work on the other side but that will involve replacing a rusty and crooked horizontal union. Thanks for telling me where to look.

    PS, not a pressure issue. The dial never budges and when I open the escape valve at the top of the boiler the steam comes out leisurely.

    SteamMan, had serious water hammer last year but when redoing the floor found a short horizontal section under the floor with a 2 inch reverse pitch. All quiet now.

  2. Because you have standing water that is condensing the steam very quickly or because you’re running too much pressure which is lifting water in the return that falls once the burner shuts off.