A: Drawbacks might include the initial installation cost, increased energy to keep water hot, and potential added wear to the water heater and plumbing over time.

Another benefit is that passive systems provide near-instant hot water. That’s because they rely on natural thermal convection rather than pumps that must be turned on manually or remotely triggered by electronic sensors.

A: A demand-controlled system triggered by a button or motion sensor activates the pump when hot water is needed. This minimizes energy and water waste by circulating hot water only when required.

Consider a flow-stop situation, like one that might naturally occur at the end of the day (Figure 4). If you look closely, you can see that a small pebble has lodged in the #2 check valve. Now imagine some sort of back siphon event over night. Perhaps a nearby building fire leaches the water back with the draw of a fire hydrant; or a pump station fails; or a water main breaks. Because the #2 check valve is not closing, all the water that has been delivered to the building will continue to flow out the relief valve until the private lines are cleared. If this is a four story building, that’s a lot of water.

A: The system continuously circulates hot water throughout the home’s plumbing, ensuring hot water is readily available at all taps. It can work on a timer or be demand-driven, activated by a switch or motion sensor.

A: Installation times vary widely, from a few hours for simple, retrofitted systems to a day or more for comprehensive installations in larger homes or systems integrated during construction.

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At the heart of it is a recirculation pump installed on your water heater. It pumps heated water from the heater directly to plumbing fixtures. When the water in your pipes begins to cool, the pump kicks in and sends it back to the water heater to be reheated and recirculated.

Tankless water heaters, on the other hand, heat water on demand as it is needed, rather than storing hot water in a tank. This means that there is no standby heat loss, and hot water is always available on demand. .

A: There are two main types: full recirculating systems that connect to the water heater and fixtures and under-sink systems that serve individual faucets or areas of the home.

In California, there’s one notable exception. If you live in an area prone to droughts, where water use is closely monitored and restricted, a recirculation system can dramatically lower water consumption for a family.

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A: Benefits include immediate access to hot water, reduced water waste, lower water bills, and increased convenience and comfort in the home.

On the downside, there are more efficient paths to near-instant hot water — tankless water heaters, for example — that don’t require added pipes or pumps.

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Watch the video below for an example of RPZ flooding and to see just how much water is discharged when a small amount of debris becomes lodged in the device.

Hot water recirculation systems are generally more expensive to install and maintain than tankless water heaters, but they can provide immediate hot water at every fixture in the building. Tankless water heaters, on the other hand, are generally more energy-efficient than hot water recirculation systems, and they can provide hot water on demand without the need for a dedicated return line. However, they may not be able to provide hot water to multiple fixtures at once.

A hot water recirculation system moves heated water around your plumbing so that it arrives at the tap in a fraction of the time.

This hydraulic valve and its placement makes the RPZ virtually fail-safe but it comes at a cost to the area around the device.

Passive recirculation is a more energy-efficient approach. It relies on natural convection and thermal siphoning. Warm water rises from the water heater; cold water replaces it at the lowest point of the plumbing. This creates a looping effect in which water circulates without mechanical input.

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The Double-Check Assembly (Figure 1) was developed in the 1950s for the fire industry. Any time the pressure on the property (downstream) side exceeds the pressure on the city (public) side, the two redundant check valves close stopping the backwards water flow. There are two problems with the Double-Check backflow preventer. First, no remedy exists in the event of a malfunction of the valve closures or if debris in the water line causes the valves to not close completely. Second, and this is the big problem, there is no way to know when such a failure has occurred without conducting a full test by a qualified professional.  The Double-Check is a closed system. It has no method of revealing whether the internal check valves are functioning properly and no way to detect the presence of debris that is impeding full closure.

In a large home, hot water may travel through 50 feet or more of piping from the water heater to the shower, the kitchen sink, or wherever else it’s needed. And while you’re waiting, all that cold water ahead of it goes down the drain and into the municipal sewer system.

Have a question about a backflow preventer enclosure?Click the contact us button below and one of our experts will be able to help with your specific enclosure needs.

The main thing to take away from this is that both backflow prevention device types perform the same function when they are operating properly, but only the RPZ is designed to protect the public water supply by disposing of any backwards-flowing water if any of the check valves or the relief valve fails.

Passive hot water recirculation systems require additional piping to work. An extra pipe runs warm water back to the heater to complete the circuit in some configurations. In other systems, warm water crosses over to the cold water pipes to return to the hot water tank.

Both hot water recirculation systems and tankless water heaters have their pros and cons, and the best option for a building will depend on a variety of factors, such as the size of the building, the number of fixtures that requiring hot water, the energy efficiency goals of the building owner, and the budget.

When a flow stop occurs, both check valves close. At that moment, the relief valve opens and evacuates the water between the valves. (Figure 3) Some think that this event defines the limit of how much water can ever flow from the RPZ into a drain. This is not so.

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A: Regular maintenance can include checking the pump operation, ensuring the timer or sensors are functioning correctly, and occasionally flushing the system to remove buildup or debris.

Passive systems cost more to install but require less maintenance. There are no moving parts to break down. They can save thousands of dollars over their lifetime compared to active recirculation with a continuously running pump.

A: Yes, a hot water circulation system can improve a home’s energy efficiency and provide the convenience of instant hot water, making it more appealing to potential buyers.

We’ll let you know what makes the most sense for your home, budget, and lifestyle: tankless heater, insulated pipes, hot water recirculation system, or a combination of two or more technologies.

Hot water recirculation systems keep hot water circulating through the plumbing lines of a building, so that hot water is immediately available at every fixture or appliance that requires it. This is done by installing a recirculating pump and a dedicated return line, which allows hot water to circulate continuously through the plumbing system.

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A designer may specify one of 2 types of backflow prevention devices. First, the Double-Check Valve Assembly. This is often shortened to DC and is typically thought of as the appropriate solution for low hazard conditions. Second, the Reduced Pressure Zone Valve Assembly, often shortened to RP or RPZ, is thought of as the appropriate solution for high hazard conditions.

Comfort and convenience are the clear benefits of hot water recirculation systems. Near-instant hot water is a luxury you may appreciate on a cold January morning.

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A recirculation system will add a small value to your home. But convenience is the only compelling reason to install one.

You’ve heard these phrases and acronyms repeatedly. If you are a designer, you feel sure that you are expected to know what they mean. Here’s a quick rundown on what they are and how they differ.

Now consider a full failure of the #2 check valve, like one that might occur if the device is knocked out of round or has a mechanical failure. It’s essentially the same event with the exception that due to the larger valve opening, there is actually a higher flood rate. Now you have water flowing through the relief valve at full head pressure. Again, if this is a large or multi-story building, that’s a lot of water very fast.

A: While these systems use additional energy to circulate the water, models with timers or on-demand controls can minimize energy consumption, making them more efficient and environmentally friendly.

How do you determine hazard? The simple answer is that the purveyor determines it, but every jurisdiction is different. Every city has its own list of named examples for what constitutes the hazard threshold. Here is an example from Washington DC. They also stipulate that if the anticipated use, as you know it, is not named explicitly, then they reserve the right to make the decision during plans review. It’s also important to understand that you cannot, as a designer, over-protect the incoming water service. This means there is no penalty for providing the higher degree of protection.

A: Systems with timers can be programmed to run only when hot water demand is highest, such as mornings and evenings, saving energy and reducing operating costs.

The Reduced Pressure Zone Valve Assembly (Figure 2) consists of two independently operating check valves just like the Double-Check as well as a hydraulically operated differential relief valve located below the first check valve.

An old house with short hot water runs might not benefit from a recirculation system. Insulated pipe is often enough to cut “wait time” for hot water.

If you’re building a new home, your best option is to work with your plumber and architect to design a passive water system that quickly and evenly distributes hot water.

The system includes a bypass valve, allowing you to control how much hot water goes into your plumbing and when the pump turns on. You can turn off the recirculation and save energy when you’re away from home.

A: Hot water circulation systems can be retrofitted in most existing homes. However, the complexity and installation cost can vary according to the home’s plumbing layout and the type of system selected.