Monthly Archives: January 2012

DWV details

Let’s leave the potable water plumbing behind and circle back to the drain-waste-vent (DWV) system.

You may recall reading about the rationales and details of the 1st and 2nd floor DWV system and looking at the installation description all the way to the roof vent.

With everything installed and documented I can now compare the schematic layouts and diagrams to the real thing.

To keep us in compliance with the Chicago and State of Illinois plumbing code, all the DWV plumbing is connected to the city sewer. But we structured the plumbing for future separation of the greywater from the blackwater without the need to open any walls. At that point we would collect, filter and store the greywater for later reuse.

Greywater stack

The future greywater system begins in the basement at the drain water heat recovery (DWHR) unit, which we placed at the bottom of the greywater stack.

The horizontal leg that currently connects the DWHR to the sewer can in the future be replaced with a small greywater collection tank that holds a sump pump and has an emergency overflow connection to the sewer.

Atop of the DWHR is a double wye, which connects to the primary greywater source, the 1st and 2nd floor showers. One leg serves the 1st floor bathroom floor drain, the second leg connects to the 1st floor shower drain, while the third leg is set aside for the 2nd floor bathroom.

If we follow the greywater stack from the basement up to the 1st floor, we find the shower drain vent that ties into the floor drain vent, effectively forming the greywater vent stack.

The leg we set aside to drain the 2nd floor bathroom continues towards the ceiling where we placed a simple wye. One branch serves the 2nd floor bathroom floor drain while the other branch connects to the 2nd floor shower drain.

Once we continue to follow the greywater stack from the 1st floor up into the 2nd floor, we can identify the floor drain and shower vent that connect to the main vent stack from the 1st floor. The stack is turning up, over and around the corner towards the main sewer or blackwater stack.

Blackwater stack

The four inch diameter blackwater stack is located in the plumbing wall with two vent lines to either side.

The two inch pipe to the left vents all of the basement plumbing. The kitchen sink vent also ties into this pipe, while the kitchen drain connects to the blackwater stack.

To the right of the stack is the two inch vent for the 1st floor toilet. The bathroom lavatory vents into this two inch pipe, while the drain connects again to the blackwater stack.

Looking at the plumbing wall from the other side, we see the 2nd floor toilet connection and vent towards the ceiling.

Moving up to the 2nd floor, the kitchen and lavatory drain are identical to the 1st floor layout, with both draining into the blackwater stack.

A little up we connect the plumbing wall vents. On the right we have the kitchen sink vent and vent from the 1st floor. To the left we have lavatory vent, the vent from the 1st floor and the 2nd floor toilet vent.

Toward the top is the vent stack connection from the showers and floor drains, before the stack turns over and up through the roof.

The only item visible on the roof is the five inch vent section of the stack.

Even though the bathroom lavatories are connected to the blackwater stack, we have a future plan for reusing the greywater from these sinks. There are simple and small filtering and storage systems, that would fit under the lavatory. The collected water would then be used for the toilet flushing,


Plumbing installation – useful gadgets

Here is a little more information about two useful gadgets in our plumbing system.

The previous post lists the rationales behind the hot water routing and makes mention of a hot water circulation pump. Let’s start with that.


I was referred to a product that would help us to cut down on energy and water waste. It is an on-demand hot water pump by D’MAND®Systems.

Typically, the pump is installed under the fixture that is farthest away from the hot water tank. It is activated with a push button or motion sensor and begins to prime the hot water line. In that process hot water is brought close to each fixture along the hot water line, providing almost instant hot water.

Graphic by:

The most common location for the pump is under a sink, which makes the installation very easy. It is shipped with the needed fittings for a quick retrofit. The package includes two flex lines to connect to the existing hot and cold water lines under the sink.

Our fixture at the end of the hot water branch is the shower, not a sink. That means that I will have to install the pump into the plumbing wall.

We did provide a hot and cold water stub to which we can connect the pump. But I am not ready to trust those stainless steel flex connectors. Not in a plumbing wall where access will be difficult.

Instead I opted for a hard plumbing connection. In other words, I used copper pipe and fittings to connect the pump.

The pump will be plugged into a GFCI outlet in the plumbing wall. Once that outlet is connected, we can pressurize the plumbing system and test-run the pump.

Edit: The on-demand hot water pump is now available at one of the home improvement big box stores (TacoGenie 1/40 HP Hot Water Recirculating Pump with Undersink Kit)

Pressure reducing valve

The pressure reducing valve in the shower riser is the second item I should point out. I gave this nifty gadget some mention in a previous post, but it may be
worthwhile to bring it up again.

The reason for the pressure reducing valve is the shower head, or to be more precise, the desire for a reliable 1.5 gallons per minute (gpm) low-flow shower head.

The one product we found to work really well, in that you get a stream of water that is powerful and does not feel like a trickle, is the Oxygenic® BodySpa® SkinCare™ Shower Head. But it is rated with a 2.5 gpm flow rate – at 80 psi water pressure.

To guarantee a low flow rate of 1.5 gpm for our showers, I’ll have reduce, control and stabilize the water pressure, as can be seen in the graph below.

The graph doesn’t seem to be entirely accurate, nor the dial settings on the pressure reducing valve. We found out when we were field testing what pressure would really get us the desired 1.5 gpm.

Once we had dialed the pressure reducing valve down to 25 psi, the shower head delivered the targeted 1.5 gpm low flow rate.

Should we decide to change the shower head in the future, which may require us to increase the water pressure, we can simply adjust the dial and thereby the pressure on the pressure reducing valve.


Plumbing installation – hot water routing

I mentioned the tree analogy that guides the plumbing layout in a previous post. Conventional wisdom is to have a trunk line with branches to each fixture.

In our case, conventional wisdom would have dictated three hot water branches serving the three hot fixtures – kitchen sink, bathroom lavatory and shower.

In order to minimize water and energy waste while cutting down on the hot water delivery time, we decided to rely on an on-demand hot water circulation pump. The on-demand pump, once activated, will take a few seconds to prime the hot water trunk and branch line.

But this throws a wrench (pun intended) into the typical trunk and branch layout. We don’t need to reinvent the wheel, but have to fall back on recent developments in the hot water routing business.

To get the most out of the on-demand system, all three hot water fixtures should line up in series on one branch with the pump placed at the end, just prior to the last fixture, which in our case is the shower. The branch in turn supplies hot water to each fixture through short twigs.

We need to be mindful of the branch routing to keep the twigs as short as possible. The shorter they are, the more it cuts down on the hot water delivery time.

Data published by my friend and hot water guru Gary Klein, which I had listed in a previous post, makes for some simple math with interesting results.

  • The hot water twig to the kitchen faucet is about 36 inches long, delivering hot water from the primed branch in less than 1 cup (0.64 cup, to be precise). The corresponding hot water delivery time is less than 2 seconds at a fixture flow rate of 1.5 gallons per minute.
  • The hot water twig to the bathroom lavatory is about 40 inches long, delivering hot water from the primed branch in less than 1 cup (0.71 cup, to be precise). The corresponding hot water delivery time is less than 5 seconds at a fixture flow rate of 0.5 gallons per minute.
  • The twig to the shower head also is about 40 inches long delivering hot water from the primed branch in less than 1 cups (0.71 cup, to be precise). The corresponding hot water delivery time here is less than 2 seconds at a fixture flow rate of 1.5 gallons per minute.

I think it is fair to say that this qualifies as almost instant hot water delivery, once the on demand pump has primed the trunk and branches.

The priming would be initiated through the push of a button, typically first thing in the morning on the way to the bathroom, or in the early evening after the first person is back home from work. Anyone else using hot water after the priming and first use literally has instant hot water. That instant hot water lasts for two hours or more, thanks to the pipe insulation we used on our plumbing system.

This is not your typical approach to plumbing installation. It requires getting used to and focus on the part of the plumber to avoid falling back into the conventional trunk and branch system, which does little for water and energy conservation.


Plumbing installation – pipe insulation

Plumbing lines in conventional projects are rarely insulated. That is despite a number of good reasons to do so.

Pipe insulation will prevent condensation on the cold water lines and heat loss on the hot water lines. With that in mind, we plan to generously insulate all cold and hot water lines.

It doesn’t take much to slip the pipe insulation over the pipe sections during the installation. Remembering to do so is sometimes hard part. Once an installer is on a roll, it is easy to forget about the insulation. Ten feet of copper piping later, he either suddenly remembers, or I get to remind him.

There are small areas around the turns and connections that do not receive pipe insulation yet. We want to leave the copper tubing in these areas accessible so that we can safely solder everything together. Once the plumbing is finished and pressure tested, Cathy will again fit insulation around these spots until all tubing is nicely wrapped and covered.

There is another good reason for slipping the pipe insulation over the lines during installation.

Without pipe insulation plumbers tend to install the copper tubing right next or very close to the framing. That makes it easy to attach the pipes with brackets.

The problem is that there is no room left for pipe insulation.

If the copper tubing can’t run next to or close to the framing, wood blocks are used to attach the brackets.

Again, there is no room for pipe insulation at the wood block.

If the pipe insulation is slipped over the tubing while it is installed, these problems disappear by default.

It makes everyone’s life easier, once the ‘getting used to it’ hurdle is tackled.


Plumbing installation – pipe size and fittings

At this point, and for quite a while, it is all about getting ready for the open cell foam insulation on the 1st floor.

Each unit is separated from the others by an air barrier – a two to three inch layer of open cell foam in the ceiling. There are a few tricky areas that represent a potential breach in the air barrier envelope.

One of the bigger potential breaches is the plumbing wall.

The plumbing wall is meant to be sealed between floors with spray foam insulation. That is once all the utilities (mainly plumbing) that run through it are installed. Half of the plumbing (the drain-waste-vent system) is in place. What is still missing is the fresh water or copper plumbing.

Plumbers usually know what to do with their eyes closed – as long as the project follows conventional construction practices. If you have read a few blog posts, you will have noticed that our green rehab project is miles away from being conventional.

To get over the road bump called green building technologies, I needed to be on my toes and communicate our goals and objectives frequently to my contractors.

Pipe sizes

The conventional wisdom is to have a large trunk line – one inch or at least three-quarter inch. The branches from the trunk line are typically sized three-quarter inch and run up to every fixture. Often the pipe is reduced to a half inch just prior to the fixture. These pipe sizes would assure sufficient flow rate to the fixtures and reduce the potential of undesired pressure drop.

For the sake of energy, material and water conservation we want the copper pipe size reduced as much as it is permitted by the Chicago Plumbing Code.

Pushing the code to its limits is rather counter intuitive for most plumbers, who are used to giving preference to the larger pipe sizes. Thinking and approaching the installation in terms of energy, material and water conservation did seem to take some effort.

Long sweep elbows

Pressure drop is an issue not to be ignored when going with the smallest permitted (or reasonable) pipe sizes. To reduce friction and turbulence in the piping, we have to leave the common and inexpensive 90 degree hard turn elbows behind and switch to the less common and more expensive 90 degree long sweep elbows.

Another option is to use 45 degree elbows where it makes sense.

The long sweep elbows are typically used in hydronic heating systems, not so much in fresh water plumbing. It was thus a good idea (and necessary) to check that no hard turn elbow found its way into the plumbing by accident.