Best Of

This is best practice. Since your vent takeoff is at the ell on the end of the pipe, next best is to raise the vent not less than 8" above the ell. Higher is better.

As is, condensate will go straight into your vents and kill them in short order.

I would say it like "As is, if your boiler surges, water might go into the vent and carry some rust chunks into it will make it fail"

In normal operation the condensate gently rolls down the pipe and doesn't go anywhere but down. There is no "slug of water"

It's so cheap and easy to isolate the vents, though, I agree it's best practice to pipe it that way.

 it isinsufficient, please replace with "a 3/4 street elbow to at least an 8" nipple. Put a Gorton #1 main vent on the end."

I would say "can you show me the new Hoffman main vent that you installed? What model number is it?"

It should be a #75 that looks like this:

https://www.supplyhouse.com/Hoffman-401434-75-1-2-x-3-4-Straight-Steam-Main-Air-Valve-8038000-p?utm_source=google_ad&utm_medium=Shopping&utm_campaign=Shopping_X_Heating_X_SSC_ClassA&gad_source=1&gbraid=0AAAAAD_WAyu15jEgIsIaPfwyCBCVnJPvJ&gclid=CjwKCAiApY-7BhBjEiwAQMrrEWLkjZJ-xQWJWVLC09I-6Wnh5acXodz9WBAF1HgKWyA4gRndaPSZJRoCP7sQAvD_BwE

Just for your information, when we say a given vent is insufficient, we mean it is too small in venting capacity to successfully vent a main. We don't even know for sure if the vent above is large enough, but it sure looks to me like you have a radiator vent on your main currently and that would be too small. Plus it looks old. But you can tell better than I can from the photo.

And as I recall, the Hoffman main vent above is about the same capacity as the Gorton #1 so if they are in love with Hoffman and want to install that, that is fine.

The additional fittings, the elbow and nipple, are to physically isolate the vent from the main pipe to protect it from water in the main. This is pretty standard stuff that should not be a surprise for them.

Actually it is just a straight run with the exception of 1 small rise in elevation of about 6 inches.

The boiler is in line with the border of the yellow and red buildings at the far right and the line ends in the basement below the sidewalk of the second storefront.

Low pressure, two pipe, steam. Thought I mentioned that but I didn't. Editing now. Thanks for the heads up.

3 choices take your pick

1 Take the supply valve off the pipe. Get a piece of clear poly tubing at the big box and cut one end on a 45 and stick the other end in your shop vac hose and tape it tight and try to work it all the way back to the main

2 Dump water down the pipe and see how fast it drains. But if you wash debris into the main you may just move the problem to a different location. Or it might spread out the debris so it will not be a problem

3 Cut the pipe off between the 45 and the main and remove or snake or flush out the debris and put it back together with 2 shorter nipples and a union. But you have asbestos to deal with