boiler water line

John Shea

I've been doing some troubleshooting on a two-pipe, gravity return vapor system.

Last week, I corrected a venting problem, and a problem with the pitch on a wet return. The system ran better (pretty good) all weekend, however, when I checked on it this morning, the Pressuretrol kicked off the burner (after about 5 min.), then the waterline almost disappeared (if not did disappear) for a moment.

The LWCO started feeding water, then after a minute, the pressure dropped and the burners kicked back on.

Now, just before that, I did drain the bottom off about 5 gallons, however, this being a 1,500,000 btu boiler (not sure what water capacity) I would not think that this would cause the SUDDEN BWL drop.

Any ideas are very welcomed.