CPVC has a C-Factor of 150 at installation, and that smoothness remains fairly constant throughout its life. Stainless steel, however, has a C-factor of 130 at installation, but that can dip considerably over its life.

A recirculating pump is relatively affordable. So even if you save less than $120, it can still pay off quickly. The time saved might be enough to justify the initial cost, even without a major reduction in utility bills.

Understanding the efficiency with which a fluid can pass through a piping material is a significant step toward ensuring the long-term reliability and cost savings potential of certain materials.

How much money does a hot water recirculating pump really save? While it can save some, it’s mostly for convenience. “In 12 months, they can save you roughly $120,” says Griccino.

How does a hotwater recirculating pumpwork

Fluid Pressure (Fluid Head): Technically, pressure head is the amount of energy within the fluid caused by pressure put on it. This is most relevant when considering pressure loss, and the corresponding pressure drop.

In industrial plants, we often discuss what is being conveyed in the pipe as a function of system design. How a material performs with respect to corrosion and temperature resistance when interfacing with different fluids is a significant consideration during system design.

One common factor in flow rate design is the size of the piping systems. To reduce capital costs, some engineers may decrease the pipe size to increase the flow rate. Adversely, higher flow rates can diminish the life of metallic system due to erosion and possible surge pressures.

Optimizing the flow rate of an industrial piping system is one important factor to an efficient system. In the resource article, Metal v. CPVC Piping Systems — Can CPVC outperform metal piping in industrial applications?, our team of engineering and product experts compare CPVC piping to metal in terms of temperature, pressure, and corrosion resistance, cost and safety.

Pipe Diameter (D): The larger the pipe diameter is, the slower the flow velocity will be. Optimal flow rate can be maintained without increasing the velocity, if a larger pipe is specified.

Hotwater recirculating pumpwith return line

In general, engineers try to design systems that balance cost with efficiency and reliability. In other words, which specific system will (a) fit a budget, but not (b) inflate energy consumption and also not (c) require excessive repairs and maintenance in the future.

“The recirculating pump costs about the same as operating a 25-watt light bulb,” says Umberto Griccino, a commercial plumber and HouseGrail consultant.

Decreasing the velocity of fluid in an industrial piping system not only improves efficiency, but can also reduce the likelihood of pipe damage.

Hotwater Recirculating pumpwith temperature sensor

Metal is more likely to lose smoothness and consistency over time due to its inherent proneness to scaling and corrosion.

In plastics, erosion is typically not a concern. Rather, there are design targets that need to be considered based on the type of plastic.

Many systems turn on and off automatically to keep the water within a specified temperature range. Others run on a timer. Both options use less energy than a continuously-running system.

Hotwater recirculating pumpinstallation diagram

When you turn on the tap, how long does it take to get hot water? Letting it run can waste money and water, not to mention time and patience.

As the equation below shows, flow rate is positively correlated with velocity—as the speed of the fluid increases, the amount (or volume) of fluid passing through the pipe during a given time period also increases.

To optimize the flow rate, some engineers attempt to minimize how much pressure is lost throughout the system or the pressure drop from one point to another.

Velocity of fluid (v): As flow velocity increases, pressure loss also increases and efficiency decreases. The general rule of thumb is to maintain a velocity below 5 ft/s (1.5 m/s).

In general, higher fluid velocities result in worse efficiency—increasing energy expenses—and lessen system reliability—as damage to the pipe becomes more likely.

Tankless hotwater recirculating pump

Hot water recirculating systems need little maintenance. Keep an eye and an ear out for leaks or unusual sounds. If you do run into a problem, Griccino says call a plumber immediately. Barring any malfunction, you should get about 10 years of use from the pump.

Hotwater recirculating pumpreddit

Flow Velocity: Velocity is the most straightforward term, as it is the average speed of a fluid flowing through the pipe. Think of flow velocity like you consider the speed of your car. Except, instead of recording flow velocity in MPH or km/h, fluid is typically in m/s or ft/s.

Griccino says a hot water recirculating pump costs about $200, and many comfort systems can be DIY installed. Better to go with professional installation if you need new plumbing.

One solution ensures you’ll never have to wash your hands in cold water again: a hot water recirculating pump. These handy devices are game changers.

Friction (f): Friction against the fluid flow is wasted energy. The friction factor cannot be changed by system configurations or designs, and is a constant for each material in this equation.

Best hotwater recirculating pump

Pipe length (L). Friction pushes against the flow, resulting in pressure loss as the pipe length increases. Pipe length also factors in fittings, which increase the “length” input for the equation.

When discussing the efficiency of fluid running through a pipe, it’s important to establish the definitions of a few terms up front:

The second type, called a comfort system, is cheaper and a much easier choice for existing homes, says Griccino. The unused heated water runs back through the cold water pipes. Since it uses the same pipes for warm and cold water, there’s one major drawback: It takes longer to get cold water. A system with a temperature sensor can correct this problem.

The coefficient used to compare materials is the Hazen Williams C-Factor—the higher the coefficient, the smoother the pipe service. The following formula is used to calculate water velocities, head-losses and pressure drops, where “C” is the material’s Hazen Williams C-Factor.

A hot water recirculating pump attaches to your water heater. It circulates hot water throughout your pipes to keep it readily available at the faucet. It’s affordable and doesn’t waste water. (Psst! Here’s how to save money this winter on your energy and water bills.)

The first type is best for new construction. Along with the usual hot and cold lines, a plumber will install a third pipe to return the unused hot water, usually between the water heater and the furthest fixture. A full system like this is expensive and difficult to install in an existing home.

There are two main types. One requires an additional plumbing line to send unused water back to the water heater after it drops below a set temperature. The other returns the unused heated water via your existing cold water pipes.

Proper piping material selection and system design controls the flow rate and velocity in a way that minimizes energy costs. Reasons for this:

If money was no object, a system could be significantly over engineered with very large pipes. This would keep the fluid moving slowly and experience very little friction loss, but would be very expensive to purchase and install.

Much of the water sitting in those pipes was once heated. Without a recirculating pump, it’s left in the pipes to cool. That’s a lot of water, energy and money down the drain.

Hotwater recirculating pumpwithout return line

To compare one piping material to another for optimizing flow rate, smoothness of the piping interior from installation through its service life is the most relevant factor.

To save more water, combine a hot water recirculating pump with water-efficient appliances and fixtures. A dual-flush toilet and efficient shower head go a long way toward cutting utility bills.

According to the National Resources Defense Council (NRDC), studies suggest that “over 10 percent of all the hot water drawn for showering in a typical single-family home is wasted waiting for hot water to arrive.”

DIYers should install the pump near the water heater and power source, and the sensor valve at the fixture furthest from the heater, Griccino says. Turn off and drain the water heater before beginning work. If you’re unsure about your DIY plumbing ability, contact a pro.

Nearly equal in importance is how the fluid is moving through the pipe. Flow rate plays a significant role in determining a system’s longevity, as well as its day-to-day energy consumption.

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