Water level dropping in classic furnace

[petefrom bearswamp]

Lately I have noticed a pronounced drop in water level in my furnace.
About an inch in 4 days.
I burn year round as I used to burn slabs from my mill.
Had the opportunity to shut down for a week and a half and noticed no drop in water level in 8 days.
Filled it back up 2 days ago and no drop since then either.
Burning now and will keep an eye on it to see if something magic has happened.
I suspect a leak in a coupling.

[barbender]

I have a fitting that leaks on mine if I let the fire go out, and the pump is still circulating.

[thecfarm]

I had a leak in my OWB. It was one of the fittings on the lines. I rubbed my hands on that lines for days. Finally I noticed it, well felt it. The leak was on the backside of the line.

[dougtrr2]

I had an HS Tarm that started seeping around the welds on the stays between the inner and outer  plates.  They were clearly robotic welds and the ones that started seeping were all in the same place, where the weld started/stopped.  It took a while to realize where the seep was, since the fire evaporated the water as fast as it came out.

Doug in SW IA

[hedgerow]

When my Garn started leaking two years ago this coming Dec that how it started it was low on water I filled it up couldn't find a leak and the water level stayed ok for a while. With Garn's you batch burn. Then the crack got worst and I could see were it was leaking were the main burn chamber was welded to the the front of the unit. I just kept adding water to get me threw till spring and then about 20 pounds of 7018 rod and two pieces of metal repaired the 12 inch crack and a couple other places that were going to fail soon. So far so good its been well over a year since the repair and all is well. I run it year around also to heat my domestic water.