I appear to have a small leak somewhere, as I lose pressure over a day or two. (My boiler, that is - not me personally). I pressure tested everything when I put the system together, and there are no visible leaks anywhere. I have had a little seepage around shutoff valve stems - never enough to be wet, but enough to have some deposits of various colors. I've tightened all the packing nuts, but it seems like there must be a good deal more leakage than that could account for in any case. More details: If I pressurize to 20 lbs, I'll be down to 15 the next day and 10 in another couple of days (all pressures with boiler near room temp). It won't drop much below that. I don't know the flow rate through my refill plumbing, but it seems like 10psi to 20psi takes several quarts at least. Outside the boiler room, there are NO visible leaks or seepages. The basement and main floor plumbing is almost all exposed, but there's a fair amount of plumbing in the walls and ceiling for the top floor zone. Even so, I'd expect a quart of leakage would show on the sheetrock somewhere. Anyone have any ideas or personal experience with this kind of situation? Any suggestions for troubleshooting steps? I'm considering pressurizing to 20psi and shutting off a couple of zones for a couple of days to see if that can isolate the problem.