Plumbing – material conservation

I got a little distracted by the recent weather events, but let me return to the fresh water plumbing system in our house.

In a recent post, I listed three major objectives: water conservation, material conservation and energy conservation. We covered water conservation, which leads us to the issue of material conservation.

Compact layout

An efficient — or better — a compact floor plan leads to material conservation in a plumbing system. Go into any building constructed around 1900 and you quickly see what I mean. The water heater is typically placed right next to the plumbing wall in the basement, which continues all the way up to the top of the building. The kitchen and bathroom are placed back to back alongside the plumbing wall. This layout reduces the amount of pipe runs needed by placing the water heater and fixtures as close to each other as possible.

Because our house was build in 1902, we are blessed with a compact floor plan, where the kitchen and bathroom are separated by the plumbing wall. Sadly, this efficiency is not very common in our over-sized contemporary homes, where bathrooms and kitchen are often scattered through all four corners of the building.

We won’t need much copper tubing for the new plumbing system, because we can keep our pipe runs as short as possible. This is good news. Copper has a pretty large carbon footprint. The less we have to use of it, the better.

Also, copper tubing and the associated fittings are expensive. With that in mind, material conservation pays off – literally.

The water conservation impact

Let’s mix material conservation with water conservation, and we’ll get an interesting result.

We established the benefits of low-flow fixtures. An added benefit of low-flow fixtures is that less water is delivered to the point of use (shower, faucet, toilet, you name it). This in turn allows us to reduce the pipe sizes in the plumbing system.

Well, only up to a point controlled by the Chicago Plumbing Code, which has not yet quite caught up with the arrival of water conservation strategies and low-flow fixtures. The smallest pipe size allowed is 1/2 inch (Chicago Plumbing Code – Chapter 18-29-604.5  Size of fixture supply). With some low-flow fixtures, though, a pipe size of 3/8 inch would do the job.

As a matter of fact, look under your kitchen and bathroom sink. There you will find the faucet water connectors (flexible tubing that connects to the faucet), which in most cases is 3/8 inch. That is OK according to code. You just can’t have 3/8 inch tubing in the wall. Too bad!

The tree analogy

I mentioned my friend Gary Klein, the hot water guru, in my recent post. He explained to me how to manage and minimize pipe sizes in a structured plumbing system by using a tree analogy.

The pipe from the water heater in the basement to the 1st floor and 2nd floor is called the trunk (trunk line), which also has the larges diameter (3/4 inch to the 1st floor and then 1/2 inch to the 2nd floor). The trunk has to convey the largest water volume out of all pipes in the system, thus the larger diameter.

Connected to the trunk line, we have branches (at 1/2 inch diameter) that deliver the water to the basement plumbing, 1st floor plumbing and 2nd floor plumbing respectively.

Connected to the branches, we “could have” twigs (at 3/8 inch diameter), with each twig servicing one outlet, i.e. the bathroom faucet. I say “could have”, because code won’t allow us to use 3/8 inch tubing. So, instead of twigs, we have the branches at 1/2 inch diameter servicing each fixture.

Smaller tubing sizes means also overall increased friction. To reduce pressure loss, potable water systems PEX tubing would be ideal. It requires less fittings (such as elbows) and has softer bends and turns, which minimizes pressure losses. But again, our Chicago Plumbing Code is standing in the way, only allowing copper tubing for potable water systems.

To reduce pressure losses with copper tubing, Gary Klein  insists on using the uncommon long sweep 90 degree elbows, rather than the typical hard 90 degree ones. He is also a fan of using 45 degree elbows instead of 90 degree ones, where possible.

There is another benefit to using small diameter tubing – an energy conservation benefit, which I will get to in the next post.

About Marcus de la fleur

Marcus is a Registered Landscape Architect with a horticultural degree from the School of Horticulture at the Royal Botanic Gardens, Kew, and a Masters in Landscape Architecture from the University of Sheffield, UK. He developed a landscape based sustainable pilot project at 168 Elm Ave. in 2002, and has expanded his skill set to building science. Starting in 2009, Marcus applied the newly acquired expertise to the deep energy retrofit of his 100+ year old home in Chicago.

3 thoughts on “Plumbing – material conservation

  1. Based on ASHRAE pressure drop calculations, there is more pressure drop in two 45 degree elbows than in one standard 90 elbow.

  2. When looking at the image of copper fittings above, I immediately wondered about the exact thing that Vaughan points out.
    But- when Marcus states that “He (Gary Klein) is also a fan of using 45 degree elbows instead of 90 degree ones, where possible” I don’t think it means that Mr. Klein recommends two 45’ss instead of one 90. I think he recommends two 45’s instead of TWO 90’s. Picture a northbound pipe that needs to go west and then north some more. You could use two 90’s – keeping the pipes on the E/W and N/S axes – OR you could use two 45’s to run the pipe diagonally. This would also have the added benefit of less pipe being required. (Less pipe to manufacture and transport; less pipe to buy; less pipe to fill with water…)
    I hope this helps.

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