Loosing water in the sight glass

ronm301

I have a steam boiler Weil-McLain model#EG-50. Few minutes after the fire comes on, the water in the sight glass disappears. However, the low-level cut off does not sense low level and the fire remains on. Few seconds after the thermostat reached its set-point and the fire turned off the water in the sight glass reappeared to its original level. I tested the low level cut off by intentionally draining the water from the boiler and it seems to work - The red light turned on and I could not start the boiler. Recently, I replaced all the vent valves in the system but this did not seem to solve the problem. Also, it seems that the level in the sight glass disappears when the the pressure starts to builds-up. Its maximum pressure is about 1 psi.

I would appreciate if you can point me to the right possible cause to this problem.

Paul48

Near-boiler

Can you post some pictures, so we can see the near-boiler piping?

ALIGA

sounds like you have wet steam

i have a similar issue where the water drops from say the halfway mark on the sight glass to about a .5" inch from the bottom of the sight glass. once the boiler turns off the glass goes back to half level.



i think the fix is lower pressure, in addition to dual risers into a drop header.