Category Archives: plumbing

Roof vents

It was nice that our roofing crew took care of the roof tear off. That gave me the space and time to focus on the little side projects, like the roofing vents.

Let’s start with the main roofing vent, or the main drain-waste-vent (DWV) stack, if you want to call it that. It services the laundry room, main bathrooms, and kitchens.

Back in 2011 we decided to slightly rearrange the bathrooms. That meant we had to move the main vent stack over by about four feet in the plumbing wall.

Rather than punching a new hole into the roof to surface the vent stack, I put a kick into the stack right under the roof so that I could surface it through the existing hole of the old vent stack.

That was meant as a temporary solution, and now was the time to discharge the temporary and build the permanent.

With the roof torn off, it was easy to cut out the temporary stack. We abandoned the awkward kick right under the roof and filled it with insulation. We cut a new hole that was centered right over the main DWV stack and reconnected it. This way the stack runs in a straight line from the basement slab to the roof – the way it should be.

And then there was the need for a whole new vent stack, which services the 2nd bathroom on the 1st and 2nd floors. We again cut a hole that was centered right over the stack and connected it.

These are the kind of connections you want to do while you are re-roofing. This way the roof penetrations become part of the waterproofing system, rather than another patch to your roof.

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2nd floor on demand pump

My current modus operatus is wrapping up loose ends. This includes the installation of the on demand hot water pump on the 2nd floor. But this time I did it with confidence, because I had the installation experience from the 1st floor under my belt, including a correction.  And I had the helpful hands of our friend Rubani assisting me.

What is this on demand hot water pump all about? Here is the super short version:

The on demand pump is activated through the push of a button. It pulls water from the hot water line and pushes it into the cold water line. Once the pump senses a rise in the water temperature, it shuts off. This primes all fixtures on the hot water branch the pump is connected to, effectively cutting the delivery time of hot water to seconds.

The on demand hot water pump is just one piece in the puzzle of an efficient domestic hot water delivery system. If you haven’t caught my earlier posts on this system, let me provide you a brief summary with links:

When you are in your bathroom or kitchen and turn on the hot water, do you have to wait for a minute or two (or longer) for the hot water to arrive? Is so, you do not have an efficient hot water delivery system. An efficient delivery system cuts the wait time for hot water to arrive to a few seconds, as mentioned above.

And it does more: It reduces water waste and as such helps with water conservation. It also results in material conservation, as the ground rule for an efficient domestic hot water delivery system is a compact layout and smaller pipe sizes (made possible through the water conservation efforts).

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You find that in an efficient domestic hot water delivery system all pipes are insulated and that it effectively manages structural and behavioral waste of hot water, which again feeds into the water conservation mentioned above.

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An efficient hot water delivery system relies on structured plumbing rather than the traditional trunk-and-branch layout. With a structured plumbing system, the on demand pump is placed at the end of the one hot water branch that services all fixtures.

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Disturbing study

Out of all systems we touched during our deep energy retrofit, the domestic hot water plumbing revealed the most unexpected surprises and opportunities – and as it now turns out, potential risk.

An article published in Environmental Science: Water Research & Technology by William J. Rhoads, Amy Prudena and Marc A. Edwardsa states:

“This study raises concerns with respect to current green water system practices and the importance of considering potential public health impacts in the design of sustainable water systems.”

(Environ. Sci.: Water Res. Technol., 2016,2, 164-173)

The researchers point to increased residence time of water in plumbing systems that have been built with water conservation (i.e. low flow fixtures) and efficiency in mind to get their green building credits. To quote hot water guru Gary Klein:

“…the rules for sizing the piping do not have a way to account for these lower flow rates and fill volumes. On top of that, standard engineering practice is to add a safety factor on top of the calculated design. The result of this tension between the plumbing code, engineering practice and water use efficiency has the effect of dramatically increasing retention time in the piping.”

That increased retention – or – residence time comes with risks:

“Concentration of 16S rRNA and opportunistic pathogen genus level genetic markers were 1–4 orders of magnitude higher in green versus conventional buildings.”

(Environ. Sci.: Water Res. Technol., 2016,2, 164-173)

A write up of the study was published in Chemistry World.


Let’s unpack this by taking a step back:

Thanks to Gary Klein, we have an efficiently structured plumbing system that maximizes energy, water and material conservation.

Well – maximizes with a lowercase “m” because the Chicago Plumbing Code got in the way. ½” is the smallest fixture branch (or twigs) size that is allowed (Chapter 18-29-604.5 Size of fixture supply). Yet the combination of our structured plumbing system and low flow fixtures validates 3/8″ fixture branches (twigs) and fixture supply lines, which would help keep excessive residence time at bay. This is a matter of right sizing the piping for fixture branches (twigs) and fixture supply lines to match the flow rate of the fixture they serve. Gary Klein puts it this way:

“lower flow = smaller water volume to deliver = smaller pipe sizing”

The 3/8″ fixture branches (twigs) may be unimaginable in Chicago, but other places have caught on to the smaller pipe sizing principle, as I found out when visiting my friend Oliver in Sweden.


I have come across a lot of bitching and moaning about the Chicago Building Code and inspections. Yet I learned to appreciate the code and the inspection through the process of our deep energy retrofit. Even if some things seem cumbersome and over the top, it is with our safety and welfare in mind. And the plumbing code is unambiguous about it:

“18-29-101.3 Intent: The purpose of this chapter is to provide minimum standards to safeguard life or limb, health, property and public welfare by regulating and controlling the design, construction, installation, quality of materials, location, operation, and maintenance or use of plumbing equipment and systems.”

Chicago, I am glad you watch my back! Except that sometimes you don’t. Sometimes the world is moving faster than you are. And everything having to do with green building is picking up speed every year. That includes encouraging developments in water conservation and low flow fixtures. I am sure ½” fixture supply pipes once were a rock solid safety standard – before the emergence of low flow fixtures. But these days… As Gary Klein points out:

“Reducing flow rates without reducing pipe volume is a recipe for disaster, as the study points out.”

Will I swap out all of our low flow fixtures with regular ones? Nope, not yet. And Gary gave me a little peace of mind:

“You actually were able to reduce the volume [and residence time] by the way you did the [structured] plumbing.”

Dear Chicago: I would appreciate it if you would live up to your health and safety intent. Take note of the study “Survey of green building water systems reveals elevated water age and water quality concerns” and adjust the plumbing code to allow smaller pipe sizes. Stay abreast of the green building developments, and in the process keep us safe – keep watching our backs!

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Back porch plumbing

Before we get to finishing the porch top, let’s take a step back and look at the very bottom. I still have some underground plumbing to finish so that we eventually can pour the concrete floor at the basement level.

A large part of the underground plumbing was already finished. We had removed the old grease trap with the temporary connections last year and connected the sump discharge to the sewer line. More recently, I extended the sewer line past the new back porch footing and took care of the footing drains.

Floor drains

The cast iron soil pipe (CISP) work that was left to do were two floor drains and their respective vents.


Yes, you read right – two floor drains! One won’t cut it and here is why: First, there is the centrally located, or general floor drain. If water spills into the back porch basement level, this floor drain should pick it up.


The second floor drain is located toward the east end and has two functions.

  1. It should pick up liquid from a future composting toilet if we chose to install one. There are a variety of composting toilets on the market. Some are self contained and others rely on a processing tank. Those with a processing tank may require a drain for small amounts of liquid discharge.
  2. It should allow me to drain and winterize the water system in the yard. We plan on an underground cistern that feeds several faucets throughout the yard with the collected rainwater. I don’t plan to install the plumbing system that connects the cistern with the faucets below the frost depth. Instead, the system has a low point at the back porch from which I can drain it, and thus winterize it.


Raising the sump

If I want to pour the concrete floor in the back porch basement level, I have to raise the sump. in other words, the sump basin rim has to be at the same elevation as the planned concrete floor.

No problem. I knew that I had to raise the sump by six inches, so I got myself two three inch concrete adjustment rings and mortared them atop of the existing sump pit.

Last but not least, I extended the future sump discharge to the planned cistern through the sleeve I provided in the foundation wall.

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3/8 inch and flowing

“I told you so!” – was coming to my mind while looking at the plumbing in a Swedish single family home built sometime in the 1970’s.

Some plumbing lines were partially exposed to keep them in the interior conditioned space. What caught my eye right away was a 3/8 inch branch (or twig) coming off of a 3/4 inch trunk line.


The use of 3/8 inch plumbing lines (or twigs) fits right with the material and energy conservation goals of an efficient domestic hot water delivery system, as was explained to me by the hot water guru Gary Klein. The problem for us in Chicago is that the smallest allowed pipe diameter per plumbing code is 1/2 inch. The rationale behind this limitation is, so I assume, concerns about pressure drop and insufficient flow capacity. But it also puts a limit on the efficiency of our hot water delivery system.

Seeing that a built 3/8 inch twig line didn’t cause the world to implode was rather exciting. Not only that, but the 3/8 inch cold water line services three fixtures: 1) the toilet, 2) a sink, and 3) a shower, while the ? inch hot water line only serviced the sink and the shower.

plumbing-041 plumbing-042



The structured plumbing system that I have described in a previous post, recommends the use of 3/8 inch twigs. But each twig should just service a single plumbing fixture, not multiple fixtures.


Serving three fixtures with cold water and two fixtures with hot water using a 3/8 inch twig lines would take us – so one could argue – into deep water. That begs the question: Why would several fixtures on one twig be acceptable?

The bathroom in the Swedish single family home is meant to be used by a single person at a time. In other words, you shouldn’t need to worry about somebody flushing the toilet or using the sink while you take a shower.

And I used that shower. There was no problem with the water flow rate or the water pressure, despite the nine feet long 3/8 inch twig. And being the nerd I am, I let the shower run while flushing the toilet or turning on the sink faucet. There was a very brief but minor pulse in the shower’s water flow, but other than that, no detectable flow reduction or pressure loss.

For full disclosure, I should mention that the bathroom in question was on the 1st floor and only a few feet away from the water heater and water main. The second floor bathroom has a different set up. Here a 1/2 inch twigs (or branches) services the various plumbing fixtures, probably to mitigate pressure loss that may come with the elevation and friction that comes with the longer pipe run.

Now – is that 3/8 inch twig I observed an exception? Apparently not. I noticed almost the exact same setup in a restaurant men’s room — a 3/8 inch twig servicing all fixtures.

As unscientific and nerdy as this is, I am delighted to see proof that 3/8 inch twigs can work and can be safe. But to whom can I take my “I told you so?”

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