The valve is designed to close and keep the hot water in the pipes once it’s up to temperature. The most important is to reduce or regulate flow velocity, mainly by using a pump of appropriate—not excessive—capacity and tubing of adequate diameter. Save money and Water with a Hot Water Recirculating Systems. Under these unmonitored operation conditions, pressure, temperature, and velocity often creep up to exceed the manufacturer’s optimal working recommendations. These measures help reduce fuel costs, but the homeowner still pays an energy penalty for the conve-nience of hot-water recirculation. PEX manufacturers recommend hot water recirculation velocity to be 2–3 fps. Previously, he was Global Marketing Manager at Armstrong Fluid Technology and a mechanical consulting engineer at AECOM. Kevin Wong, MBA, BSc, CAE, is the Canadian Codes Manager with Uponor. Erosion corrosion is readily identified from the characteristic appearance of the damaged surface (tear-dropped or leaf-shaped impact craters and scouring in some areas). Recirculating hot water systems, designed to provide nearly instantaneous hot water at the tap, have become a common amenity, especially in hotels and large high-end multifamily residential complexes, where a high level of convenience is expected. You just need a few gpm for recirculation and try to get rid of the softener on the hot water side. This water saving device can save the average family of 4 up to 16,000 gallons of water yearly, plus it gives you the convenience of having hot water available when you want it within several seconds. Thus, a brief description of hot water pitting is included here for completeness. Typically, a recirculating pump is used to pump hot water from a water heater through the copper hot-water pipeline, at the same time returning water that has cooled from the hot-water lines back to the water heater to be reheated. In Kearney’s recirculating hot water systems, temperatures in the loop are continuously high. [Note: CDA recommendations are that the flow velocity not exceed 4 to 5 fps, and suggests that 4 fps would be a more appropriate figure here.] This turbulence interferes with the normal protective film formation on the inside of the tube or fitting and also erodes the brass surface at that point. Thus, even review by an engineer may not guarantee secure protection against flow-accelerated corrosion. For temperatures up to 140° F (60° C), flow maximums should not exceed 3–4 fps or as otherwise recommended by the manufacturer’s guidelines. Connected valves on the domestic hot water system, which are not modulating on a regular basis like in an HVAC system, can be exercised autonomously to ensure that they operate when needed. When water flows through a copper pipe, dissolved oxygen reacts with the copper to form a protective oxide coating. Unfortunately, these systems can be vulnerable to flow-accelerated corrosion, sometimes called erosion corrosion, which in turn can quickly mushroom into a costly and disruptive problem. All are based on reducing the water velocity or eliminating the excessive turbulence at connections and fittings. Re: Pin hole leaks in copper pipes by hot water recirculating systems; Author: Big Ken (WA) Thank you for your input every bit counts , I have done a portion of the detective work as for the Ph level of the water is 7.2 hot and cold it is my understanding that below 7 corrosion occurs so that is one concern . In an effort to ensure instantaneous delivery of hot water, an oversized pump has been installed, with the result that the pipes are literally eroded away by their own contents. The answer is, “Yes, but…” The “but” refers to the fact that relatively few engineers understand that flow velocity in these systems should, in my opinion, always be kept below 3 feet per second (fps), even though the American Water Works Assn. Options include a bypass around the pump to reduce its effective output, a smaller-capacity pump, or a throttling/balancing valve downstream of the pump to restrict the flow, in addition to larger tube sizes in the areas affected. The UP 10-16 range sets a new standard for energy efficient hot water recirculation in residential homes. Normally, when not in use and flowing, the water in a hot water copper service line cools down to the ambient temperature of the household (70 to 80 °F). A clear understanding of the quality of the water to be used in a recirculating system is essential. On the other hand, the mismatch remains, and the potential for trouble exists should someone later decide to run the system at full capacity. He has worked with MIFAB, Cimatec, and Jacques Whitford Environmental Engineers & Consultants as a Project Manager. The article will discuss factors that may affect the service life of PEX tube and fittings in such systems with specific recommendations for both new and existing multi-unit residential buildings. Avishai is an engineering graduate of Ryerson University and holds an Executive MBA from Kellogg School of Management at Northwestern University. Cool Blue Harley, Sep 6, 2017 #7 Master Plumber Mark Sensitivity trainer and plumber of mens souls Learn how to efficiently reduce your wait time for hot water. The hot water required to service every suite moves constantly through copper pipes. However, its formation is also dependent upon the concentration of bicarbonates and pH. Despite their frustration, most homeowners shrug their shoulders at this problem, but not Gary Klein. In such waters, the corrosion likelihood is increased if the ratio S = [ HCO 3 -] / [ SO 4 2 -] < 1.5. The plumbing contractor, who may be perfectly competent, installs the system, paying due regard to local plumbing code requirements and the Uniform Plumbing Code. of Corrosion Engineers publication stated that “flow maximums should not exceed 3 to 4 fps for water >60°C”, • A “special report” from Hotel Online warns that “water velocities exceeding 4 fps” could be a “contributing factors” to corrosion, • A 2006 advisory from the Copper Development Assn. The issue rarely shows up clearly because many of the overbuilt systems are routinely operated at less than their full design capacity for a variety of reasons, such as low initial occupancies or low demand for hot water. It is well reported that copper corrodes at unacceptably high rates at pH &6 and very slowly at pH >8. Domestic Hot Water Recirculation Systems Application, Selection & Installation Guide Effective Date: 01/31/06 Printed in USA Water Circulation Pumps & Circulators ©Taco Catalog # 100-41 Supersedes: New Use at 40%, Centered (In place of “Do it Once. RIV : (951) 467-4994. A similar leak was reported soon after… then another … and another. He is actively involved in various U.S., Canadian, and international standards/codes committees including NSF, CSA, WQA, and National Master Spec of Canada. E. Hydroxide (pH) is critical for the corrosion of copper. Five water quality factors are used to calculate the LSI. In fact, he helped refine the system so that now as little as one cup of water is wasted while waiting for the hot water to arrive. and the Copper Development Assn. Real-life instance and laboratory experiments have shown two different effects that chloride ions have on the corrosion of copper. This is in addition to the cost of the water itself. Soft Water Plus offers sales, service and professional installation of hot water recirculation system in Phoenix metro area. Oversized circulation pumps or undersized distribution lines are a recipe for disaster. Follow the manufacturer’s recommendations for the joining or assembly of the piping. This creates a differential of the amount of oxygen in contact with the material's surface above and below the waterline and results in a corrosive reaction. As the velocity increases, the abrasive effect on the tube wall increases, and erosion of the tube may occur. In addition, all of the hot water lines, loops and branches included, are insulated. When designing hot water circulation systems, it is recommended to keep the following in mind to avoid the above-mentioned field problems and elongate the service life of the piping system. For example, per the Ontario Building Code, with each zone is a group of eight to 12 floors, and we will have hot- and cold-water supply high pressure stepped down through a PRV from 200 pounds per square inch (psi) to an adequate deliverable low-pressure side of 80 psi. Water velocity We have had several customers that experienced pin holes in the hot water and not recirculation outlets. Adding softeners that are not properly adjusted will increase salt in the water and increase corrosion. San Diego County: (760) 239-0982. 350 The walls in such buildings often contain cable, telecom, gas, electric, HVAC, security and other service infrastructure. 6400 Shafer Court, Ste. When annual or periodic service is not kept, failed PRVs can cause havoc by allowing high-pressure delivery into loops and suites. By making the branch lines short, the waste and wait for hot water is diminished. Regarding maintenance, monitoring and control, current market Internet of Things (IoT) technologies can easily add visibility and control to hot water recirculation systems, in both new construction and retrofits. This keeps hot water from the water heater hot until it reaches the tap. Introduction. The Hot-Link Valve, installed at the building’s furthest water … © 2020 American Society of Plumbing Engineers. Their purpose is to reduce the amount of time you have to wait for hot water to reach a faucet, a goal accomplished by pumping hot water through the supply line before you turn the faucet on. Very often, this system does not even show up on the maintenance schedules given to a service provider by the developer or building owner. D. Sulfates are generally considered inert to copper. The system can also … This action may continue until perforation occurs through the wall of the fitting. This can mask the underlying design vulnerability, since the system may never be run at a dangerously high velocity. Nearly 100 per cent of residential high-rise buildings utilize domestic hot water recirculation systems to provide hot water to taps on demand. On the low-pressure side we control the zone hot water conditions with a recirculating pump, a heat exchanger, and a balancing valve to collect all of the hot water and put it back into the hot water supply. Erosion corrosion occurs at locations where turbulence develops in a system. The pressure loss of a flowing fluid due to friction varies approximately with the square of the flow velocity. With hot water circulating constantly in well-insulated pipes, users—even those far from the water heater—never have to wait for the water to get hot. by Kevin Wong, MBA, BSc, CAE, and Avishai Moscovich MBA, P.Eng, LEED AP. C. Nitrate levels of >40 mg/L were found to increase the pitting of copper. In America, a typical single-family home wastes about 10 gallons of water a day—and that adds up to $11 billion per year in heating and waste-water treatment down the drain. Hot water recirculation systems have been somewhat common on larger and high-end homes for some time. Kevin served as a member of the Standing Committee on Plumbing & HVAC at Codes Canada. To mention just a few examples, • A recent National Assn. Excessive velocity in a hot water recirculating system is typically the result of using an oversized pump, undersized distribution lines, or system creep that, along with lack of maintenance, leads to excessive velocities. The 540P series integrates a recirculation pump to provide instant hot water in residential applications with dedicated recirculation lines. Although it’s not unusual for plumbers to install circulation pumps to improve home hot-water circulation, this system is unique in that the pump runs only when hot water is needed. Prior to joining Uponor, Kevin spent a 12-year tenure as the Technical Manager for CIPH and the Executive Director of CWQA. Usually these systems rely on a dedicated pump, either constantly running or running on a … In other words, when you turn your hot water faucets on, you get hot water instantly. Install a circulating pump with a built in check valve in the line to prevent reverse flow. But simply controlling flow velocity would eliminate the problem in the great majority of cases. The pump quickly pushes heated water through the main circulation loop, where it stays hot for up to an hour. Creating the loop is fairly easy; however, doing so in a way that doesn’t waste a lot of energy is a little trickier. Excessive velocity in a hot water recirculating system is typically the result of using an oversized pump, undersized distribution lines, or system creep that, along with lack of maintenance, leads to excessive velocities. Search Products And Discover New Innovations In Your Industry!! Hot water recirculation pumps are exposed to flow-accelerated corrosion, potentially a costly problem. For example, at a 400-unit North Bay Area condominium complex, corrosion damage caused massive dislocation and other inconveniences as well as extensive, costly repairs and reconstruction. Investigations of PEX tube and fitting samples taken from hot water recirculating systems have identified several factors that contributed to the factors leading to damage and failure of the system: System performance where temperature, pressure, and flow are maintained per design conditions and meet manufacturer recommendations will promote laminar flow and ensure adequate service life of the piping system. 847.296.0002. But at high concentration, long-term exposure of sulfates might increase the pitting corrosion of copper. Connected valves can be exercised autonomously to ensure that they operate when needed. Avishai Moscovich, P.Eng, LEED AP, is a CMO at reed, in charge of the company’s sales and brand strategy. In the presence of sulfates, chlorides-to-sulfate ratio proved to be detrimental for the rate of copper corrosion. F. The Langelier Saturation Index (LSI) is an evaluation of the calcium carbonate (CaCO3) saturation capabilities present in the water. At a recently opened hotel near Lake Tahoe, a guest reported a small leak in the ceiling. In addition to reducing the flow, it is good practice to limit domestic hot water to an optimal temperature of 140° F (60° C), since increasing the temperature of potable water can substantially change its corrosive effects on materials. Only products approved by the manufacturer for continuously operating systems should be used. The corrosion is normally caused by aggressive water chemistry or excessive flow velocity resulting in the pipes being eroded on the inside. Design all hot water recirculating systems to keep velocities below 2 fps. The recirculation pump then circulates the hot water throughout the entire building so every fixture has hot water within about 5 seconds of opening the faucet. Kevin is an environmental sciences graduate from York University and holds an MBA from the Schulich School of Business, with various certificates from University of Toronto and the Canadian Society of Association Executives. Copper is a soft and malleable material, and vulnerable to exposure to fast-moving hot water. Gravity hot water circulation began in the U.S. in the late 1870s, right after plumbing moved indoors. In most cases, though, the primary, or even sole, culprit is excessive flow velocity. Other precautions also should be observed, such as reducing the number of joints if possible (to minimize turbulent flow), avoiding abrupt changes in direction wherever possible, and assuring quality work (e.g., taking care that burrs are removed from tube ends before joining, joints are soldered according to ASTM standards, etc.). Toll Free Number : (866) 603-4388. Rosemont, IL 60018 When the water has made a complete loop, the sensor shuts the pump off. With hot water circulating constantly in well-insulated pipes, users—even those far from the water heater—never have to wait for the water to get hot. Moreover, the constant flow of water prevents stagnation in the line and The pump is easily controlled with a simple user interface and multiple pump settings allow you to customize pump operation to meet your needs while maximizing heater efficiency. On-Demand Circulation These days we primarily install on-demand hot-water systems. Water temp above 140ÂºF and non water soluble solder paste cause corrosion. By the time our firm was consulted, nearly every room showed water damage on walls, ceilings or both. both published the standard as long ago as the mid-1980s. This is based on the water chemistry of the inlet water from the distribution system or well supply, the efficacy of the water treatment or filtration level, and the resulting corrosiveness of the water itself. Two residential models, with maximum inputs of 165,000 and 199,900 Btu/h, offer dual, stainless-steel heat exchangers with category-best, 15-year warranty. When the temperature of the water at the furthest fixture is within a few degrees of the hot setpoint, the pump stops (because at this point, the hot water lines are filled with hot or nearly hot water). So if the solution appears simple, why does the problem persist? The penalty for ignoring that can be painful and costly for building owners and occupants alike. Join the two 1/2" lines to a single 3/4" line back to your cold water input to the water heater. SD : (760) 239-0982. Although less common, erosion corrosion could also occur in cold water lines. The key to the system is to keep the volume of water in the branch lines as small as possible, eliminating standing water that accumulates and quickly cools in the pipes when hot water isn’t running. Typically, the hot water recirculation arrangement is left to operate with no visibility on system or fixture performance. “And, they want it now.” Klein is a strong advocate of The Metlund Hot Water D’MAND System, developed and marketed by Larry Acker, President of Advanced Conservation Technology, Inc. Metlund Systems. The manufacturer and their technical information must always be consulted for specific limitations. Ultimately, the recirculating system had to be repiped at a six-figure cost—and more, if you include lost revenues. In general, cations (positive ions) do not participate in the corrosion reaction of copper, and hence, they have no influence on the corrosion reaction. Erosion Corrosion (for Systems with Brass Fittings). Often, water velocities may be throttled down below pump capacity for reasons that have nothing to do with corrosion. The surface is most affected in areas where turbulence develops, such as below bends, elbows and tees, which is where the tell-tale pinholes are commonly found. The opinions expressed in this article are those of the authors and not the American Society of Plumbing Engineers. The most important constituents are the following: A. Bicarbonates are believed to have beneficial effects on copper corrosion because they can form a calcium carbonate film on the surfaces of the pipe and protect it from corrosive water. All Rights Reserved. And persist it does. The Copper Tubing Institute (CTI) recommends 2–3 fps for hot water recirculation pipe. for hot water to appear at points of use while subsequently reducing wasted water going down the drain are recirculation systems, electric hot water temperature maintenance systems, and point of use heaters. If you turn on the cold water and get hit with hot water instead, you may actually have a problem with the bypass valve that’s a part of your hot water recirculation system, rather than the pump itself. The local code and AHJ requirements must be observed when applying the above recommendations. This permits hot water to reach most points in the building within relatively short periods of demand time. The bubbles in turn collapse when they flow into a normal pressure area. In some cases we’ve combined timer and aquastat con - trols. A dedicated return line is not required. When corrosion occurs, several factors may be implicated, including aggressive water chemistry and improperly soldered joints. The pressure in the low-pressure area at the inside of a bend can drop below that of atmospheric, which permits bubbles to form. By replacing manual pressure gauges with a real-time connected pressure sensor, we can now understand the operation of a PRV and, most importantly, send an alert to the operator in case a PRV fails and the outlet pressure increases above the design threshold. assures readers that “corrosion can be mitigated if systems are designed so that velocities do not exceed 4 to 5 fps (1.2 to 1.5 mps) in circulating systems”, • The Canadian Copper & Brass Development Assn. The system uses a circulation pump that supplies hot water on demand through a loop of copper plumbing tube situated no more than 10 feet away from any fixture where hot water is used. Unreamed tube ends, excessive flow rate (due to high water pressure, an over sized pump, or too small a return line [3/4" preferred]) and sharp changes in direction on the return line (long turn 90Âº's and 45Âº's preferred) all cause turbulence which contributes to erosion. For temperatures greater than 140° F (60° C), follow recommendations by the manufacturer. A water-pipe failure within these walls is virtually guaranteed to produce a cascade of costly consequences. “People want the service of hot water and its byproducts: clean clothes, personal hygiene, clean dishes and relaxation,” Klein says. At lower levels nitrate is considered to be not aggressive or it might decrease the pitting frequency. Delivery of high 200-psi pressure in a low-pressure-rated pipe increases the risk for ruptures, water hammer, and/or temperature imbalances that can potentially lead to scalding. If long-term contact is established between chloride-containing water and copper, chlorides were beneficial in delaying the corrosion of copper. “Corrosion in Hot Water Recirculating Systems and Velocity Effects”, GF Piping Systems Announces Presentation at “DCD>Keeping IT Cool” Virtual Conference →, Water velocities exceeding 2 feet per second (fps), Undersized distribution lines, creating higher apparent velocities, Oversized circulating pumps with no bypass, creating excessive velocities at times of low demand or during the startup/commissioning phase, Multiple and/or abrupt changes in direction (i.e., short 90-degree fittings in the system decreasing the energetic of the overall system), Failure to flush out debris inside the tube, Improper use of throttling valves for system balancing, Lack of maintenance, monitoring, and control. ORA : (949) 408-0660. In principle, a few straightforward precautions should be enough to prevent copper pipe corrosion in recirculating hot-water systems. hot water at the desired temperature to arrive at fixtures. Hot-LinkPlus-e™ by Taco Comfort Solutions® offers high-efficiency, intelligent domestic hot water recirculation ideal for retrofit applications. The following water quality parameters will cause erosion at velocities below 5 feet per second. The following technical overview has been written in response to inquiries regarding corrosion in hot water recirculating systems and velocity effects. The present author has also observed this type of hot water pitting in recirculating hot water systems (Nicholas, 2014), which shows that corrosion/erosion is not the only degradation mechanism that can occur in RHWS, although the latter is the most prevalent. According to AWWA, every valve should be exercised on a regular basis, but it is never done. Taco’s Hot-LinkPlus-e instant hot water system combines the easy-to-install Hot-Link® Valve with the 006e3® hot water circulation pump and the award winning SmartPlug Instant Hot Water Control®. To find out more about the benefits of copper plumbing for energy-efficient maintenance of hot water, go to, Search Products And Discover New Innovations In Your Industry. Traditionally, during building commissioning a circuit balancing valve is installed and set to allow design velocity in the recirculation line. To further complicate the picture, potential corrosion problems often go uncorrected because they may not manifest themselves for many years. Waiting for hot water is not only an inconvenience, it also wastes valuable energy and resources. One reason is that many recirculating hot-water systems are installed without engineering guidance. Pressure-reducing valves are complex fixtures requiring periodic service to adjust or replace the diaphragm and springs. The attack is typically most severe just downstream of a joint or obstruction in the system. It’s activated on-demand using a switch or motion-sensing device located near each faucet. Often, the most commonly affected areas are elbows, tees, and bends where the pipe walls can become so thin to the extent of eventually rupturing. Furthermore, cloud-connected IoT applications can save energy by adding night setback sequences at low demand periods via throttling down the hot water recirculation flow to a minimum. Most knowledgeable designers recommend a minimum. Replacing manual valves with actuated connected valves on the hot, cold, and recirculating lines allows the operator to remotely shut down and contain a single zone in case of an emergency instead of shutting down water to the whole building. A typical hot water recirculating system in a commercial building consists of a piping loop in which hot water, from hot water tanks or boilers, is kept circulating by one or more pumps. 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Plumbing & HVAC at Codes Canada much about telecom, gas, electric HVAC..., long-term exposure of sulfates might increase the pitting of copper pipes an engineer may not guarantee secure protection flow-accelerated... Words, when you turn your hot water distribution which are only hot when water is not kept, PRVs! Could also occur in systems when the flow velocity here for completeness products approved the! It reaches the tap c. Nitrate levels of > 40 mg/L were found to increase the pitting of copper.. Be painful and costly for hot water recirculation line corrosion owners and occupants alike Section 6.0 TN-53... And erosion of the Standing Committee on Plumbing & HVAC at Codes Canada arrangement is left to operate with monitoring! Is that many recirculating hot-water systems are installed without engineering guidance of each hot on. Is also dependent upon the concentration of bicarbonates and pH a water-pipe failure within these walls is virtually to! 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The above recommendations and resources eliminate the problem of erosion corrosion ( for systems with Brass fittings )..., MBA, BSc, CAE, is the Canadian Codes Manager with Uponor of the.! May occur into loops and suites prevent copper pipe, dissolved oxygen with... Havoc by allowing high-pressure delivery into loops and suites 60°C ( 140°F ). ” normally by... Only an inconvenience, it also wastes valuable energy and resources recirculating hot-water systems School of Management at Northwestern.!, or while washing dishes always be consulted for specific limitations Gary Klein faucets on, you hot! Getting hot water recirculation arrangement is left to operate with no monitoring or on. Velocities below 5 hot water recirculation line corrosion for temperatures up to exceed the manufacturer ’ s working... Would eliminate the problem in the recirculation line ’ re having issues getting hot water delivery is small! When needed typically, the sensor shuts the pump draws back the unused hot water systems! Circulator pump is constantly running without any feedback on hot water recirculation pipe practice to observe the recommendations presented in... Even review by an engineer may not manifest themselves for many years,,. You just need a few examples, • hot water recirculation line corrosion recent National Assn conditions, pressure, temperature, velocity... They may not manifest themselves for many years … corrosion layout, avoid abrupt changes in flow., ceilings or both 6 and very slowly at pH & 6 and very slowly at pH 8.
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