Single Pipe Steam - Boiler pressure is very slow to fall

OldBayOnEverything

I have single pipe steam setup that lately has not been wanting to kick on. The pressure reading is consistently in the 10-12psi range (way high!), even in the morning after the boiler has not run all night.

I presume the gauge is not faulty because the low pressure cut-in never activates, despite being cranked all the way up to 8psi, so my thought is that the pressure in the pipe at the gauge and cut-in is actually that high (or that they have simultaneously failed). If the pigtail is clogged, could that lead to permanently high pressure at the gauge and cut-in?

I'm skeptical that the boiler pressure is actually as high as the gauge is reading due to the amount of time that can go by without the pressure reading falling very much. Six or eight hours can go by and the reading won't fall more than two PSI.

Is a clogged pigtail a likely problem to suspect in this scenario? Anything else that I ought to look at?

Thanks!

SteamingatMohawk

It seems pretty unlikely that with the boiler off that the pressure would not decay overnight. Is there any chance the gauge is hanging up and there really is no pressure? Be careful how you investigate.

JUGHNE

Sounds like a plugged pigtail for sure. Pressure can push past the plug and be trapped above the plug.

Set the pressure control as low as possible.
Post a picture of both with cover off of the control.

Fred

I assume the gauge and Pressuretrol are both on the same pigtail. I'm not sure what you mean by the low pressure Cut-in never kicks in? That would imply that the boiler never turns on. Is that the case? BTW, The Cut-in should be set at .5PSI and the white wheel (Differential) inside the pressuretrol should be set at "1". It almost certainly sounds like the pigtail is clogged. If the pressure has built to 10 to 12PSI, you have probably ruined your radiator vents and your Main Vents. They should never see more than about 3PSI and, if the gauge is actually getting to 12PSI, you are getting very close to the 15PSI that will cause the boiler Pressure Relief valve to blow. You don't want that and you certainly don't want to be near the boiler when that happens. Clean the pigtail. The time it took to ask the question is not much less then the time it takes to take the Pressuretrol off and take the pigtail off and either clean or replace it.

neilc

while cleaning or replacing the pigtail,
make sure the hole it's screwed into is clear also,

Dave0176

If the pigtail hasn’t been cleaned it’s probably plugged up with mud.

Steamhead

if the pigtail is steel, just replace it with a brass one. Steel pigtails typically rust shut and aren't worth saving, since they'll rust up again.

Mike_Sheppard

It is likely a plugged pigtail as mentioned.

But out of curiousity, what is the water level in the gauge glass? Could the entire system be full of water?

OldBayOnEverything

The pigtail is cleaned out and the system appears to be operating properly at less than 2psi. Thanks for the help!

SteamingatMohawk

What did you find?

OldBayOnEverything

The pigtail was clogged shut and trapped pressure at the gauge and pressuretrol. Cleaning it out and reinstalling resolved all issues.

SteamingatMohawk

Awesome. Congratulations

I was thinking the gauge may have been overranged and damaged, but JUGHNE was right on, since that is probably more likely.