Only two radiators on this sytem get flooded with water!!!

Liquid Plumber_2

Help! I have inherited a pain in the **** heating system. Catholic school located in the Bronx. Steam system works great except for 2 radiators located on the first floor of the building. First of all the return line in the basement cafeteria shoots water 11 ft high! and the same happens to the existinhg rads above on the first floor. All of the supply piping is covered. Going to expose all this weekend but return is exposed and banging !!!!! Only half of the building return bangs!! The other locations are ok..no banging..only this one section? Why are only these two rads filling with water. Of course once water is drained rads operate properly until next cycle. Can I convert these rads only into a two pipe system with a steam trap? Or are one of the major steam traps on the return defective? Help. Thanks _Paul

[Deleted User]

I think the return line may be clogged. How often do you have to fill the boiler?