Distribution piping methodologies

Having been involved in the pipe trades for over half of my life, I have had the opportunity to be exposed to almost every type of piping system, as well as having utilized every type of piping system and methodology ever invented.

I have seen and dismantled some old gravity flow systems, and discovered that the old installers had some pretty interesting tricks up their sleeves. I plan on sharing these tricks of the trade and piping methodologies over the next series of articles.

Turn of the century home

Before we move on, I’d like to expose some of the tricks that I discovered in removing a system that was installed in 1906 for a 2.5 story brick home that was actually a turn of the century Montgomery Ward’s kit home, complete with bricks, framing and heating system.

This home was originally provided with a solid fuel (coal and wood) burning cast iron boiler. The distribution piping started out in the mechanical room as 4-in. schedule 40 mild steel piping, installed in a parallel reverse return configuration. Some of the pipe lengths were full sticks, at 21 feet in length.
One of the first things that caught my attention was the fact that every piece of distribution piping main pipe in the system (4”, 3” and 2”) was pre-cut and threaded at a remote machine shop, then delivered to the jobsite for installation.

I was amazed that the installers had the wherewithal to work in concert with the brick layers and the masons had provided four points of access through the basement walls for the long lengths of extremely heavy piping to be installed around the exterior perimeter of the home without having to cut and couple the piping if it had been brought in through the stairwells. Talk about collaborative construction meetings…

Horizontal distribution system

As I previously noted, the horizontal distribution system was laid out in a parallel reverse return configuration, as opposed to parallel direct return basis. The vertical risers were piped in a direct return fashion, which worked well for nearly 100 years prior to our coming in for the major remodel. As is usually the case, the homeowner wanted to recover the lost head space in the basement of the home that was lost to the installation of the gravity fed supply and return mains, which start low near the heat source, and gradually rise upward as they make their journey through the perimeter of the home.

The homeowner liked the esthetics of the large antique upright cast iron radiators, and in fact had us remove the radiators and ship them out to a sand blaster and powder coating company for refurbishment. We also added radiant floors in the major bathrooms (three master suites throughout the home) to increase the owners comfort levels. This all required us to install a pump forced system, and the largest pipe we ended up having to install to replace the 3-in. mains was 1½-in. copper.

It has been known in well documented hydronic systems that the hot water has a tendency to want to rise up, causing the upper floors of a gravity heated structure to overheat, thereby causing the lower floors that are being bypassed to under heat. In their efforts to spread this heat out and eliminate the major discomfort associated with hotter upper rooms, the installers would place a restrictive orifice in the radiator unions in order to create a path of greater resistance on the upper floors, and a path of least resistance on the lower floors.

If you’ve ever retrofitted one of these gravity fed systems with an electric circulator, and you weren’t aware of the placement of the restrictive orifices, then you inadvertently discovered the “paths of least and greatest resistance” because with a powered circulator, and the orifices left in place, the original problems of hot upper floors and cool lower floors is reversed!

Wise old hydronics contractors would go through all of the radiators, and pull the orifices out of the upper radiators and place them in the lower radiators in an effort to balance the system out if a powered circulator was added. Although far from perfect by any means of measure, it did help in spreading out the heat when the system was on.

Wise old hydronics contractors would go through all of the radiators, and pull the orifices out of the upper radiators and place them in the lower radiators in an effort to balance the system out.

In the process of disassembling the old cast iron fittings, and steel pipe, we used a sledge hammer to physically break the cast iron tees in order to free up the pipes, so they could be removed and recycled at the local scrap yard. Breaking tees with a sledge hammer, although somewhat caveman-ish in appearance, is actually quite efficient.

By holding a large sledge hammer behind the fitting (backer) and hitting the shoulders of the fittings with a smaller sledge hammer, you minimize energy dissipated due to moving pipes. As you are hammering on the fitting with the smaller sledge, you can hear a distinct change in tone as it goes from sounding like the liberty bell on first blows to a dull clank on subsequent blows. You will know when the fitting is ready to expire, and you’d best have the pipe secured, or make certain no damage will be done by the pipe coming loose and hitting the floor.

As we worked our way through the home, it became apparent that the pipe fitters for this system knew the issues they would be dealing with in a gravity flow situation. We discovered that all of the horizontal mains were fully reamed to full pipe size throughout. But when it came to the risers and radiator branches, it appeared that they had “forced” their cuts on the second and upper floors, causing rather prominent pipe cutting ridges, none of which had been filed to full pipe bore diameter. They were creating a “path of greater resistance” with their methods of non-reaming. This practice would be condemned by today’s stringent code standards. Whodathunk!

Also of interest was the old cast iron boiler. It was an Arco, manufactured by a local casting foundry responsible for many boilers in the Denver market. Having had experience with these boilers on numerous other projects, we discovered early on that the boilers had huge open water ways within the boilers. They were very conducive to gravity circulation with a minimum of internal resistance to flow under gravity considerations. The problem with applying a circulator to the beasts was that the water under forced circulation would bypass much of the heat exchanger. The boiler would be bouncing off of its high limits, but in reality, very little hot water was being extracted from the boiler due to water following the path of least resistance along the outer portions of the boiler jacket. Another whodathunk!

Tune in next month as we continue our discovery journey into the many methods of hydronic piping and their applications in the world of high-efficiency comfort delivery systems. If you’ve not yet joined the RPA, please do join.

This is a group of dedicated folks who are dedicated to furthering the cause of this wonderful industry. It is an organization of the members, by the members for the members with all members benefitting. Join today.

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