Last week, the plumbers did the rough plumbing for the ADU. There wasn't too much progress to point out each day, but overall, it's interesting to see and understand how the plumbing actually works. The videos below are my attempt to show and explain how the ADU's plumbing works. But, here's a quick overview of some of the significant aspects of the plumbing design.
PEX tubing is used to convey potable water to and through the ADU from the street water main. The water is about 50 degrees when it reaches Portland from the Bull Rull Watershed in the northwest foothills of Mt. Hood. The ADU's water main immediately splits when it gets to the ADU, sending one PEX tube directly to the tankless water heater (which hasn't yet been installed) to be heated. From there, one hot and one cold PEX tube is then directed to each of the main hot/cold water fixtures (sink, shower).
I've put all the fixtures (bathroom, sinks, etc) on the east side the house to minimize the amount of energy needed to pressurize and convey the potable water around the ADU. Since the house is going to be heated by hydronic, radiant floor heating, the plumbers are taking on the role an HVAC contractor would normally play in most American homes. It's interesting to note that most houses in other countries are not heated by forced air--that's an American thing. Anyhow, minimizing the number of subcontractors involved in the house conditioning gives me a little more executive control over the integrated home mechanical design and saves me and the builder some of the administrative hassle and cost of dealing with so many different sub contractors in the building process.
The sewer drain slopes toward the existing sewer in the main house through the gravel beneath the slab at a slope of 1/4" per foot. Once it joins up with the sewer drain on the main house, it is funneled out to the city sewer in the street. Finding an appropriate place to position and slope a large sewer pipe was a little more challenging due the smaller size of this structure. Sinks and toilets each have an air gap to keep any sewage odor from coming up from the sewer through those fixtures and into the house. You've probably seen the J-shaped air gaps (or traps) beneath your sinks. In order to properly drain those same pipes then, the air pressure must be equalized on either side of the waste water (or the liquid would be stuck like water in straw that you've capped with your thumb). So, each plumbing fixture has a vent to allow the sewer run to properly pressurize to allow the waste water to drain. The vents that you'll see in the video look like sewer pipes, but they're smaller.
You may have noticed the ends of these vents in your roof in in the form of 'roof jacks'. Usually, there's a roof jack for each water fixture. When designing an airtight structure however, it's a best practice to minimize the number of exterior sheathing penetrations (holes in the exterior walls and roof). So, I asked my plumber to combine all of the vents inside the house to create only one roof jack for the whole structure, instead of four roof jacks.
Ok. On to the videos. Here's an overview of the plumbing.
The two radiant loops on the 2nd floor
The roofing and skylight windows were put up in two days.