Where Did My Water Go?

First let me say that this is a great site.  I just remembered that it exists when I took out my copy of Dan Holohan's great book We Got Steam to see if I could find the answer to my current problem.   His book has helped me greatly over the years but this latest problem is a little strange and so any ideas here would be appreciated.





First the basics...steam heat, 80 year old house, lots of radiators, 300k BTU Weil McLain gas boiler on a two pipe system.



The saga...bought the home ten years ago and for the first couple of years the heat was okay but not great.   Over the last couple of years some radiators never really got hot at all.   About three weeks ago during a cold spell I put the boiler on and found that I had to fill it once a day.   After a week of this - and walking all around the house looking for wet walls, puddles etc and finding nothing, I began to suspect that I had a hole in the boiler.  I walked outside on a clear brisk day and saw that my chimney was pretty darned wet.   This helped to explain why in the last few days I began filling it almost hourly.   And I should add that I wasn't getting much steam evenly through the house.



Indeed I had noticed over the last couple of years that the chimeny was getting a white chalky look but never really thought much about it.   In retrospect I wonder if that was a sign that I was losing signficiant amounts of water from the boiler.   Back then I was filling once every couple of days.



Anyway I called a tech who came over, took a look and verified the worst.  (Let me add that he wasn't a knucklehead as he had no vested interest in selling a new boiler or doing the work)   New boiler necessary.   So I got a new one and I'm glad to report that for the first time radiators that were previously cold are now blazing hot.  It's great!   Further, whereas radiators used to lose all of their heat maybe 10 minutes after the boiler shut off, the new boiler seems to have changed the math a little because I shut my boiler as a test last night at 9:35pm and the radiator in my room stayed very hot until well after 11pm.  And this same incredible change was seen and measured at every radiator in my house.   Amazing!   I will take that any time since it's a gigantic improvement that will hopefully result in lower gas bills.



Now for the tragic news:   I've had to fill the new boiler four times in the last day.   Four times.   I again walked around the house with a flashlight hoping to find a puddle or some wet walls.  Nothing.   zip.  Can't find a single drop of  water anywhere.    Indeed, when I shut off that boiler at 9:35pm (at the boiler switch by the way) everything was, as I wrote, blazing hot until 11pm.  11:30 I go downstairs to turn on the switch to see if my low water cutoff light will come on and sure enough it does.  Warm radiators.   Light is on.  I decide to shut it again and wait for this morning. 



8am.  Flip the switch on and the low water light shines.   I look at the sight glass and there is no water to be found.  



So, where did my water go?   I suspect that there is a significant issue with one (or more) of the wet return lines - which are, of course BURIED under carpeting and about a foot of cement - but I am confused as to where my water went.   Is it as easy as the water condensing out of the radiators, finding it's way to a crack in the wet return and saying goodbye to the system - or- is there a possibility that the water is actually in the system sitting behind a clog in the wet return?   I would obviously prefer the latter in the hope that I can ask a plumber to use one of Dan's 10 ways for cleaning a wet return - rather than ripping up my carpeting and the floors.



Finally (hey, thanks for reading this by the way) the system does have a Hartford Loop so am I correct that the water in the boiler is not exiting back through the wet return via some crazy vaccuum?





Problems!   Any help is most appreciated.