Radiator or Percolator?

Big-Al_2

The single pipe steam radiator in our second floor bedroom makes a strange bubbling noise . . . kind of like an old fashioned coffee percolator, except much quieter.  It's not loud enough to be disturbing at all, but it's curious nonetheless.



It starts when the steam first arrives at the rad, and quits when the radiator is fully hot.  I thought it might be air bubbling through condensate trapped in the vent, but if I put my finger over the hole in the vent, the bubbling noise doesn't go away.  The 1 1/4" riser goes straight up from the basement vertically right to the radiator angle valve, so there can't be a pipe pitch issue, and the radiator has decent pitch too, about 1/4" in two feet.   The supply valve is only a couple of years old, and is wide open, so I don't think there is any kind of blockage issue.



Another radiator, in the dining room, also makes a noise, this time when it's fully hot . . . a faint tinkling noise, almost like one of those table top fountain waterfall things . . . like maybe the condensate might be dripping down from the columns into a pool of water in the bottom.  This radiator is also pitched correctly, but it is fairly tall and not very long . . . only seven sections.  It's a hot water radiator without a dropped bottom tapping. The bottom tapping was bushed from 2" to 1 1/2" so maybe there is a puddle in the bottom of it.  A similar radiator in the kitchen (not bushed down) is dead quiet.  Strange indeed.



OK, I'm an engineer.  By definition that makes me mechanically curious to the point of OCD.   Neither of these radiators have any real issues, but the sounds do seem rather peculiar.  This is the only place I've ever lived with steam heat.  Are these little curiosities common?  Anybody have any ideas to the cause or cure? 

Jamie Hall

Gotta love those little noises...

Think of them as soothing evidence that the boiler is working!



The dining room?  I'd bet you're right -- a pool of water trapped and little drips of condensate going into it.  And, short of lining the bottom with something (that's a joke!  Don't do it!) I can't think of a way to get rid of the puddle -- or the tinkle.



The other one?  Probably is steam or air bubbling through condensate.  A cold radiator can produce an amazing amount of the stuff... again, can't think of a way to get rid of it, given that everything sounds like it's installed OK.



Incurable, endurable?

Big-Al_2

Sure

The sounds are actually almost soothing, but they do make me curious.  I almost wish the radiators were made of glass so I could watch what's happening inside.  I'd bet there would be all kinds of interesting stuff going on as the radiator went through a heat cycle.



I was at a steam seminar earlier this year, and in the front of the classroom, right in front of where I sat, there was an illuminated live inverted bucket trap with the front of it replaced with glass.  It was absolutely fascinating to watch it do its thing . . . bubble . . . gurgle . . . fill . . .flush . . .close . . . repeat.  It was almost like a Lava Lamp, or one of those bubble candle Christmas tree lights, on steroids.

TomM

well....

if your valves are the appropriate size, and fully open, maybe the radiator is pitched too much? 

The Steam Whisperer (Formerly Boilerpro)

Percolating

Usually that sound is caused by steam filling the radiator too quickly......making condensate too fast for it to drain fast enough.  The usual culprits are 1) too big a boiler, 2) too big and air vent on the rad, 3) too many radiators shut off (makes the boiler too big.   No. 1 is almost universal.

Big-Al_2

Yep

It's a radiator with a small-ish supply and fast vent hooked to an oversized boiler.  There might be enough condensate formed to get in the way of the steam and cause a burbling noise.  The vent doesn't spit, so I'm going to keep it fast.  I like my bedroom warm, and I'm not ready to spring for a bigger radiator.

TomM

then

vent the riser fast, and slow down the radiator.  maybe.