what's happening to the water?

rdv

I'm a perplexed homeowner wondering what's happening to the water in my hot water home heating system.

Last year I started hearing some gurgling sounds when it was circulating. I tried to vent the radiators, but there didn't seem to be any air to release. Eventually I manually held the city water supply valve open (a Watts quick feed valve). The water rushed in and the gurgling went away. Since then I've been doing the same thing every week or two.
I did it a week ago, and again this morning. It ran for about 10 seconds before it started filling spilling out the relief side.

It just doesn't seem that it should be this way. Shouldn't the system be feeding itself automatically? And what the heck is happening to the water? I haven't seen any leak. Can it evaporate or sublimate that fast or must there be some hidden leak? I would appreciate any insights.

BTW, the boiler is a Hydro Therm HC125.

Thanks, RDV

[Deleted User]

sure 'sounds' like

a leak to me, and it can be small enough, and/or at the boiler, and evaporating off before you see it. it happened to me at two ball valves, and i only happened to be at the right place at the right time to see it. btw, mine had the same symptoms, but it's a closed system and it shut down on low water

Brad White_184

Take a look

at where the expansion tank connects relative to the circulator (pump). The expansion tank should connect just upstream of it. If the tank is downstream, all of that pumping energy goes to "negative pressure on the inlet side" and can suck in air because the pressure is sub-atmospheric.

It may well have been that opening your vents actually was drawing air IN to your system.

What pressure does your system maintain?

Gurgling is air more often than not- the competing forces of a compressible and incompressible fluid. Either that your you have scuba mice in your piping. I suspect air....

fission2

I had the same problem a few weeks back, and got some help here, they told me to check my expansion tank to see if it was waterlogged. I dropped the pressure in the system by purging the air/water from a top radiator, and then shut the valve off to the expansion tank, and removed it. Then made sure it was pressurized to my system pressure 15psi, and put it all back together, now the sounds have stopped.