Missing Main Vents and no plugs to install vents

OTT28

We recently purchased (fall 2015) a 1926 built home. The steam boiler for this one pipe system was replaced in 2014. We were enlightened by "We Got Steam Heat" and have identified a few problems. The near boiler piping (steam risers) are not correct according to the manufacturer's installation specifications (and heatinghelp.com dos and don'ts examples), the two steam mains lack main vents and any plugs to install them, and there is no pipe insulation (asbestos recently removed by licensed experts). We have done the simple items like replacing all radiator vents and pitching the radiators. We are planning to insulate soon. We are attempting to get a professional (no knuckleheads) steam contractor to evaluate installing main vents and redoing the risers. In the meantime as a mitigation for this heating season, would it be advisable to install a larger vent on the radiators nearest the end of the mains. Each main end has a branch to radiators. If this is advisable, what type of vent would we use and any special attachment to radiator needed (assume replace radiator vent even if upsizing with nipples and bushings)? Forgot to mention that obviously we are experiencing some cold radiators and water hammering and the assortment of expected noises from the aforementioned identified problems, that is why even a partial fix will hopefully help.

BobC

Main vents are the first step towards getting a steam system to heat evenly and quietly. If there are no fitting to attach vents to you could have thread-olets welded onto the ends of the mains to use as attachment points. You can also attatch on the side of a vertical drip at the end of a main.

Parallel or contertflow mains?
How many steam mains, how long and what size pipe?
How many radiators attached to each main?

Go over all the pipe you can reach in the basement with a level to see if everything is pitched right, old houses settle so slopes may not be right any more. Keep the pressure at 1.5PSI or less.

Bob

OTT28

Parallel system. Two 2-1/2 inch mains each about (not at home to measure right now) 12 feet long. Boiler manufacture install sheets show 2 inch risers and mains. Again, not at home to verify this but believe one main has five radiators (1st floor) off three branches. Other main has five radiators (one on 1st floor, 4 on 2nd floor) using three branches. If we cannot get someone soon for installing threadolets (thanks, great solution) could we temporarily vent larger at the closest radiators to main end points? Looking for temporary solution until can fix the right way.

Fred

One big problem with putting large vents on a radiator is that will cause the steam to race across the top or bottom of the radiator and close that vent before the air is evacuated from that radiator. The end result is that radiator will not heat up.

BobC

You could drill and tap the input side of the radiator and put a Gorton D vent on the last radiator on each main. Steam radiators usually have a ready place to drill and tap on both the first and last section of the radiator about 1/3rd to 1/2 up on the end sections. Start with a small drill and work your way up to the correct drill size for a 1/8" NPT tap

Use a small vent (4 or 5) on the regular vent position. The large vent should handle the air in the main while the small vent will vent the radiator itself. The only concern is if the radiator leadout pipe is on the small side the increased condensation might cause a problem. As i said before make sure the slope is good on the pipes.

Bob

OTT28

In that case sounds like installing threadolets for attaching main vents is the priority and really the only practical solution.

BobC

You should find a boss above the steam valve where you can drill and tap for another air vent.

Bob

OTT28

We will consider the radiator venting if we cannot get someone to install the threadolets. Assume if we cannot get a steam contractor a qualified welded could do the drill and weld. If threadolet installed on side of main, assume you come out of threadolet with nipple to 45 elbow to nipple to 45 elbow to vent or is there another recommended way of attaching main vent? BTW, what size main vent do we use; Gorton #2 or is that too big?

OTT28

Did a little more research and got a little nervous regarding welding cast iron. Anyone have opinions of drilling and welding old cast iron to install the thread-olets??

Steamhead

Shouldn't need to go that far. We usually drill and tap into the side of the last cast-iron tee on the main for 1/2" pipe thread, slightly pitched back toward the tee, screw a 3-4" long nipple into this with an elbow pointing up and install the vent. This will handle up to a Gorton #2 vent.

With this method, the reason to drill the last tee instead of the pipe itself is because the tee usually has thicker metal, which will give you deeper threads.

If the main is short and you don't need such a big vent, drilling into the side of the pipe is fine. You can install up to a Gorton #D this way, which has similar capacity to a Gorton #1 or Hoffman #75.

But on a very large job, welding thread-o-lets is the way to go. The pipe involved is not cast-iron, but wrought iron (if it's old) or black steel (if it's newer). There should be no problem welding this.

JeffM

I had threadolets welded onto the piping in my steam system a few years ago with no trouble. I was in a similar situation to you.