Saint Clair Shores has one of the highest counts of original one pipe steam in Macomb County, and many calls near Jefferson Avenue and 9 Mile Road start with water on the basement floor beside the boiler. Let's take a look. Often it's the safety relief valve, and that valve is telling us something about the rest of the system.
A residential steam boiler's relief valve is rated 15 psi. If it's lifting, the boiler went far past the 2 psi a house should ever see. We read the gauge first, then the pressuretrol. On these lakeshore bungalows we regularly find the control set at 5 or 10, or a pigtail so clogged the control never felt the pressure at all.
So we pull the pressuretrol, clear or replace the pigtail and reset the control to around half a pound cut-in. Then we replace the relief valve if it has been weeping, because a valve that lifted on dirty water may not reseat. We never cap or plug a relief valve, and we explain to the homeowner why someone else may have tried.
Last step is the boiler log. We write the date, the pressure settings and the low water cutoff test result on a card that hangs on the boiler. That card tells the next tech, or the next owner, exactly what was done, so nobody quietly turns the pressure back up to 10 a few winters from now.