1. Domestic Hot Water Recirculation
…get it hot, fast and NOW!!

2. Some Facts… Water heating is 2nd or 3rd largest residential energy use
14 – 25% of the pie
Everything’s bigger today:
Median home 50% bigger
1970: 1600 SF
2010: SF
Distance to furthest fixture increased 266%
1970: approx. 30 feet
2010: approx 80 feet
Hot water fixtures have doubled
1970: approx 6 fixtures
2010: approx 12 fixtures
18 times longer to get hot water today compared to 1970
DOE estimates family of four wastes up to 14,000 gallons of water per year
To understand the benefits of domestic hot water recirculation, it’s first important to understand some basic facts. First of all, domestic water heating is typically the second or third largest energy user in residential applications…depending on where you are and the size of the structure and the number of people living in it. Typically, that energy use can make up anywhere from 14 to 25 percent of the overall energy pie. Again, depending on climate, the larger users of energy are heating and cooling. If one were living in the Southern climates, it’s likely that domestic water heating would be the number two energy user, behind air conditioning, since heating is not as big of an issue. In the mountains, it’s possible that water heating would actually come in ahead of air conditioning as an energy user.
And along with energy consumption, there’s the issue of waiting for hot water to get to the fixture. When it comes to bathing and cleaning, the wait has gotten longer over the past 40 years. Let’s take a look back in time and compare…

3. Types of DHW Recirc Trunk & Branch Full loop recirculation
Pump and Controls
Water Heater
Full loop recirculation
Pump and Controls
Aquastat
Water Heater
Most plumbing systems in the US are simple Trunk and Branch systems, as shown here. They include main hot and cold trunk lines running through the house, with smaller branch lines going to service fixture clusters. There are several ways to incorporate domestic hot water recirculation systems with this type of plumbing.
½ loop recirculation with thermo-sensor

4. Half-Loop Recirculation Using the Cold Water Line as Return
Pump, Valve, Control, Thermo-sensor
Another option is the half-loop recirculation method using the cold water line as a return. Either a circulator or some sort of valve is installed under a sink…the circulator runs on a timer, for specific period of time. Even though water from the hot water line is circulated back to the water heater through the cold water line …it’s unlikely that much, if any, actual hot water will wind up in the cold water line. Remember that the water being recirculated is either cold or tepid – not hot. The longer the circulator is programmed to operate, the more likely you are to have some hot water make it into the cold water line.
It’s important to have some sort of temperature activated control on the system…either a sensor that will turn the circulator off when temperature at the faucet increases, or some sort of temperature actuated valve that will close when the water temperatures at the fixture are satisfactory.
Taco Plumb n’ Plug®
Timer-controlled
Analog 24 hr/15 minutes
Digital – 7 day/8 events
What does the aquastat do? Shuts the circulator off when the water in the pipe reaches 115 degrees, turns it back on at 95 degrees. Saves $$ in electricity and fuel at the hot water tank
Not recommended for tankless type water heaters.

5. D’Mand
How is D’mand pump activated? Motion sensor or push button – wired or wireless. Comes on only when water is needed.
What are the advantages to D’Mand? Most energy efficient DHW recirculation option – only runs when needed –saving electricity & fuel at the hot water tank
Under-sink installation
Another alternative is the Taco D’Mand system. As the name would indicate, the circulator operates only “on-demand.” It doesn’t work on a timer…it’s enabled by either a remote mounted push button or by a motion sensor. The circulator would be enabled only when there’s a need for hot water….a user can turn the pump on simply by pushing the button, or activating the motion sensor. The Dmand circulator can be mounted under the sink (line voltage would be needed) or back at the water heater. When mounted under the sink, the circulator is piped from the hot water shutoff to the cold water shutoff…and it uses the cold water line as a return line to the water heater. The pump will run until the internal sensor senses an increase in water temperature…when the temperature increases enough…the circulator shuts off. No timer is needed…the circulator will only run when hot water is needed.
Also, the D’Mand system is the type of recirculation system most recommended by tankless water heater manufacturers. Since tankless water heaters only fire when there’s a demand for hot water, a recirculation system that only operates on demand makes the most sense. The D’mand pump is also engineered to provide enough head pressure to overcome the high pressure drops through the heat exchanges in tankless water heaters.
Water heater installation

6. With Tankless Water Heaters
The D’Mand recirc system is also recommended for use with tankless type water heaters. Since those water heaters are typically fired based on flow, a demand type system is and ideal choice for hot water recirculation. The sequence of operation is simple…the circulator – in this example installed under a lavatory sink – is enabled by a push button or motion sensor, and pumps the cold or tepid water in the hot water line back to the water heater through the cold water line. The tankless water heater, sensing flow, will then fire to make hot water. The D’Mand circulator will run until the onboard sensor reads a specific temperature rise (5 to 15 degrees; factory set to 5 degrees but is field adjustable). At that point the circulator shuts off, and hot water is available at the fixture.
Tankless With Recirc Line

7. Hot-Link!® Timer “00” pump + bypass valve
Uses cold water line as “return line”
Integral thermal disc in valve – prevents cold water line from filling up with hot water
Closes when degree water reaches valve
Something new from Taco is the Hot-Link recirc system. The Hot Link is currently being released in the Southeast and in Texas, with wider release scheduled for the first quarter of 2011.
Hot Link uses a Taco Plumb N’ Plug circulator and a new bypass valve, to be installed under a sink. This eliminates the need for line voltage under the sink (as is required with the D’Mand pump), and eliminates the need for a dedicated hot water return line. It’s perfect for simple retrofits with tank type water heaters.

8. A Case For Pipe Insulation
Speeds up hot water delivery
What is consecutive use” DHW uses following the first use of the day, or initial use. Pipes are already hot and hot water is already at or near the fixture – reducing wait and waste.
How does pipe insulation affect water temperature drop when the water is flowing? Insulation will cut temperature drop in half while the water is flowing.
How does pipe insulation affect water temperature drop when the water isn’t flowing: The time it takes for the water to drop to 105 degrees pretty much triples when the pipes are insulation. The net affect is that when you start using hot water, it gets to the fixture both faster and hotter, and it stays hotter longer, when helps save energy in consecutive hot water use.