Early in 2003 we received a call from a distressed new building owner. The three story single family home was purchased in the summer and the heating season seemed far off. As winter approached they fired up the boiler for the first time and found that it banged so badly that sleep was next to impossible. They immediately contacted a plumber who came in a did some work, upon firing the boiler again the family realized that the banging was actually worse. It was at this point that A Real Good Plumber Inc. was contacted to do a complete survey of the entire heating system, and implement a solution.

This first picture shows the original piping configuration at the time of purchase. The vertical white lines represent the original take offs. This piping arrangement causes banging because the two steam risers from the boiler are aimed towards each other with the two take offs in between. The steam from each riser actually bumps into the steam from the other riser. This collision along with the fact that the left riser has no where to dump water, causes water to follow the steam through the pipes. Water in steam pipes is a prime cause of banging. (see line to banging pipes and velocity charts)

The first plumber they called in realized this problem and removed these two take offs and capped the two tees, which was the appropriate thing to do. The goal is to get the steam a from both risers going in the same direction. The problem was that they left the main header (see #2) back pitched and only installed one new 2” take off which they then split into two 2” take offs. This actually made the banging worse because all of the steam for the entire building now had to travel through one 2” pipe which doubled the velocity of the steam traveling in this one 2” pipe. Steam traveling at high velocity causes the steam to carry water along with it and once again water in steam pipes causes banging.

Here is the actual proposal that we sent to the customer.

These next two pictures show how we corrected the boiler piping. #1 shows the two risers from the boiler. We brought them up high so that we are at least 24” above the water line in the boiler. This prevents the water from coming along with the steam up into the header. As long as the two risers are sized adequately almost no water will come along with the steam. #2 shows how we bring the two risers together before installing any take offs to the building. #3 shows the two vertical take offs to the building.

If you look closely you will see that we increased the size of these two take offs from 2” to 2 ½”. The two overheads that travel the length of the basement, one going towards the front and one going towards the rear were 2” in size and pitched down. The original take offs were done in 2” so the “normal” thing to do would have been to use 2”. However, we did some calculations and found that 2” takes offs were a little too small to carry the amount of steam created by this size boiler. Thus we increased them to 2 ½”. It’s the little things that sometimes make a real big difference in the end result. When we left the building the boiler was quiet and the owners were now able to sleep through the night.