Flushing a two pipe radiator

JShep

On my continued quest to get our years dormant two pipe steam system running efficiently following boiler replacement, I’ve got a radiator that only heats along the top of the radiator.

First, it was clear the radiator was filled with water (diagnosed by sound… and a boat load of water coming out when I started removing the cap on the trap to check if the bellows failed).  I removed some pipes to get to the condensate riser that all the roads on this side of the house connect to… cleared a clog and the water rushed out, but the clog just moved.  Yesterday, I went into the basement and drilled, cleared, and then tapped the elbow that meets the horizontal return main back to the boiler (fortunately, with a union in the right spot, I was able to disconnect and send the crud to buckets instead of the boiler).

put it all back together… now the rad heats along the entire top instead of just the first section at the top by the valve.  I’ve confirmed I have proper condensate flow, and it’s not holding water.

rad is on the second floor… first and third floor on the same steam and return risers function perfectly.  My trap may not be working effectively, but even completely pulling the bellows and leaving the cap off, I get negligible steam coming out of the trap.  So… gotta be clogged, right?  I recently posted about a sound storm like sound up this steam main (the 3” run in the basement had a 2” sag right below and would have constantly had water in it, likely leading to rust/sediment build up… I sorted that, ultimately resulting in all that crap being in contact with the steam sending along)… my assumption is that this radiator got clogged with the bulk of the sediment (sand storm has died down), as it has a much more direct path from the main than the floor above and below (a tee and a 90, instead of a tee and a pair of 90s with longer runs back to the main).

So what’s the best way to flush the gunk out?

It’s in the back of the house with easy hose access, but big and would be a challenge to move.  So I’m thinking either connecting the hose to the valve end, connect another hose to the trap end… run water in and then have the drain house routed out back.  Or should I get a recirculating pump and put some vinegar or something in there and constantly flush it around and around?  Or something else entirely?

JShep

By the way, if valuable in terms of the best way to flush… it’s a 12 section, 6? Column (not home… but I know it’s got the broad columns on the outer edges and then and a handful of the narrower fin columns in the center.  It’s just shy of 30” tall… so not huge, but not small.  3/4” valve inlet, 1/2” trap out.