five cold radiators on three risers, I'm scratching my head

Dave in QCA

We're handicapped with partial information

Nifty, I'm not sure where to go here.  You indicated a while back that you were reluctant to show us too much of your system because there were other issues as well.  But, I am guessing that part of the problem may be that we don't have enough information to understand your system, and, as with any system, all the parts interact and effect the rest of the system.



By the way, did you do the test where you were going to turn off 3 radiators and see if the ones that are hard to heat do any better?



I noticed that in one of your pictures, you had a 2x4 propping up the main where the U is, and of course, that is the low spot for that main.  In raising that part, what you would do would be to increase the amount the rest would have to be raised.  Perhaps the intended function of the U never worked in the first place and it might have to be abandoned, but you seem to have a lot of problems to solve first.   You indicate that a long stretch of pipe that comes from the boiler is newer.  Perhaps when it was installed, it was done so in a way the lowered the pipe.  This seems quite likely.  I can see your boiler, I think, behind that hanging piece of bubble wrap.  It looks like a cast iron headed unit used to connect up all of the sections on a very old cast iron boiler.  Of course, that header has not moved, but I suspect the your new pipe turns and ties into it, and it was done without regard to pitch when it was replaced.



Also, I see a regular steam trap on the side of one of your radiators.  This is the wrong device, although, it would work.  The correct device is an "air service vavle, for Paul systems.  Hoffman #3.  Here is a link to it.  http://completewatersystems.com/wp-content/uploads/2011/04/HS900-3474.pdf       

You also indicate the there is no vents on the main and that there is not remaining device from the original system where the mains were vented into the air lines.  So, all of the venting of the entire system is occuring through the rads, and through traps that probably vent excessively compared to the original device.  Some type of main venting needs to be put back into place, either crossover traps or conventional main vents.



You've got a lot going on with this system and I would recommend that you enlist the services of a steam expert, such as Boilerpro, who is Chicago.