Under these unmonitored operation conditions, pressure, temperature, and velocity often creep up to exceed the manufacturer’s optimal working recommendations. D. Sulfates are generally considered inert to copper. Water temp above 140ÂºF and non water soluble solder paste cause corrosion. But at high concentration, long-term exposure of sulfates might increase the pitting corrosion of copper. Hot water is a modern convenience that most of us typically don’t think much about. Install a circulating pump with a built in check valve in the line to prevent reverse flow. In general, cations (positive ions) do not participate in the corrosion reaction of copper, and hence, they have no influence on the corrosion reaction. “People want the service of hot water and its byproducts: clean clothes, personal hygiene, clean dishes and relaxation,” Klein says. 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. 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. The penalty for ignoring that can be painful and costly for building owners and occupants alike. 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. 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. The system can also assist in determining if water and energy conservation measures are being met. As the velocity increases, the abrasive effect on the tube wall increases, and erosion of the tube may occur. The system can also … 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). The local code and AHJ requirements must be observed when applying the above recommendations. While this can also happen in non-metal fittings, the effects are much less dramatic due to the elasticity/plasticity of the materials and that ability to absorb some of the energetics of cavitation effects. 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. It combines a 006e3™ ECM hot water circulator with Taco’s Hot-Link® Valve and Smart Plug Instant Hot Water Control® in one easily-installed package. 1. At lower levels nitrate is considered to be not aggressive or it might decrease the pitting frequency. Brochantite due to better stability at high temperatures is commonly found in hot water pipes or hot water recirculation systems. E. Hydroxide (pH) is critical for the corrosion of copper. While the water is typically deemed potable and thus clean, there are still instances where debris, sediment, and other elements can scour the inside surfaces of any piping material, and excessive velocity increases the risk of erosion corrosion in these cases. Kevin Wong, MBA, BSc, CAE, is the Canadian Codes Manager with Uponor. Several choices for corrective action to eliminate the problem of erosion corrosion are available. 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. By making the branch lines short, the waste and wait for hot water is diminished. [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.] RIV : (951) 467-4994. 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. Very often, this system does not even show up on the maintenance schedules given to a service provider by the developer or building owner. 6400 Shafer Court, Ste. When water flows through a copper pipe, dissolved oxygen reacts with the copper to form a protective oxide coating. On the other hand, too much calcium carbonate can result in plugged pipes. “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. The phenomenon of cavitation can occur in systems when the flow velocity is high and the direction of flow is sharply changed. Despite their frustration, most homeowners shrug their shoulders at this problem, but not Gary Klein. Nearly 100 per cent of residential high-rise buildings utilize domestic hot water recirculation systems to provide hot water to taps on demand. All are based on reducing the water velocity or eliminating the excessive turbulence at connections and fittings. To mention just a few examples, • A recent National Assn. intermittent systems for hot water distribution which are only hot when water is being drawn. Recirculating hot water systems are not quite that old. Most knowledgeable designers recommend a minimum. Avishai is an engineering graduate of Ryerson University and holds an Executive MBA from Kellogg School of Management at Northwestern University. Waterline corrosion occurs when one portion of a base material is submersed in the water and another portion is in contact with the air. Only products approved by the manufacturer for continuously operating systems should be used. Often, within a couple years you will find that balancing valve has been moved and is not in the proper set position anymore, and there is no indication on the flow or water velocity in the 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. A dedicated return line is not required. Oversized circulation pumps or undersized distribution lines are a recipe for disaster. A clear understanding of the quality of the water to be used in a recirculating system is essential. Toll Free Number : (866) 603-4388. To repeat: these systems should be so designed that hot water temperatures generally do not exceed 140°F (60°C), depending on local codes requirements, and flow velocity is no greater than 3 fps. Plastics Pipe Institute (PPI) test TN-53 recommends following the manufacturer’s recommend maximum velocities in situations outside of typical hot water usage, such as greater than 140° F (60° C) or non-typical applications like constant velocity. In a fitting, the centrifugal force flowing around a short-bend radius at high velocity causes an increase in pressure at the outer portion of the bend and a resultant lowering of the pressure at the throat. Introduction. This is in addition to the cost of the water itself. 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.
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