We’ve all been there. You get up in the morning and you turn on the hot water tap in your bathroom as you stumble out to the kitchen to make coffee. You have to let that bathroom faucet run for a few minutes so the water will “warm up” enough for use. The unheated water, meanwhile, just drains away…
Let’s say the average 2,000 square foot house has about 125 feet of ¾-inch pipe, which holds about 3.14 gallons of water at any time. If your customer re-enacts the “let it run until it gets hot” scenario above 10 times a day, that means he or she may be wasting up to 31.4 gallons of water daily, nearly 12,000 gallons a year.
Hot water recirculation pumps are available from a number of manufacturers. We gave representatives of the major players an opportunity to let us grill them on what makes these systems tick. Offering up their views on the subject are Clint Andrews, HVAC product manager for Grundfos; Curtis Yarborough, technical support assistant with Laing Thermotech, Inc., in Chula Vista, Calif.; Dale Stroud, Uponor’s North American business strategy manager; and Doug Bird, product manager-water circulation for Taco, Inc.
RJ: What does a hot water recirculation pump or system do?
Grundfos: A hot water recirc. pump moves a small, constant supply of hot water from the water heater through the plumbing system and back to the water heater. This ensures that a supply of hot water is quickly available at any tap in the home.
Laing Thermotech: They recirculate the water, keeping it in the lines so it’s warm instantly when you open up your faucet.
Taco: Basically, a domestic hot water recirc. system is a piping layout that allows for continuous or intermittent pumping of fresh hot water to plumbing fixtures and return of the standing “cooled” hot water in the line back to the water heater for reheating.
Uponor: A recirculation pump allows a flow of hot water through the main trunk of a plumbing system without any taps [faucets] being open. The flowing water circulates throughout the main trunk and is returned to the water heater for reuse.
RJ: What problem in the home does it solve?
Grundfos: [Hot water recirculation systems] solve the problem of waiting for hot water. Many homes have a long run of pipe between the water heater and fixtures so we spend many minutes waiting for our showers to get hot in the morning. Your morning shower will draw it’s first bit of hot water from the recirc line noted above while the water heater “catches up” and supplies hot water for the balance of your shower.
Laing Thermotech: Well, they make it so you don’t have to wait with the water running for hot water to be available at the tap. It takes a while for hot water to run to the faucet from the water heater, particularly if you have a long run of pipe.
Taco: This type of system eliminates the nuisance of waiting a minute or two for hot water most homeowners encounter, particularly now as homes get larger with longer runs of piping between water heater and fixture units. It ensures instant hot water comfort at showers and faucets as well as huge savings of water that would otherwise be wasted down the drain. Many states or municipalities dealing with water conservation issues now mandate this by code.
Uponor: A recirculation pump addresses three issues: 1) hot water delivery time (convenience for the occupant), 2) hot water waste by minimizing water loss down the drain while waiting for hot water to arrive at a tap, and 3) energy usage by re-capturing water for which energy has been used to heat. If recirculation is employed, hot water is already near a tap. The only remaining “cooled” water that has to be purged (before hot water flows from the tap) is the water contained in the (hopefully) short branch located between the main trunk and the faucet.
RJ: What are the different types?
Grundfos: We use “Traditional” or “New Construction” to refer to systems outlined in question No. 1. These systems typically have a third plumbing pipe that runs from the water heater to the fixture furthest away from it. A stainless steel circulating pump (designed for these open systems) moves the water from the water heater, through the loop, and back to the heater. These systems are ideally installed during home construction or during a full remodel because the recirc pipe needs an unobtrusive path through the house.
A retrofit system can go in at any time. The Grundfos Comfort System uses a stainless steel circulator mounted on the hot water discharge of a typical domestic water heater. A bypass valve connects the hot and cold water lines at the fixture furthest from the water heater. The system uses the pump to move water from the water heater into the hot water system. The cold water line acts as the return line to the water heater.
Laing Thermotech: Putting them under the sink is a retrofit system for people who don’t have a dedicated return line. Most standard recirc. systems, particularly with new construction, will have a dedicated return line built in that taps into the end of the hot water supply line and beings the water back through that dedicated return line, with the help of the pump, back into the water heater to be reheated and sent back out to the fixtures. It keeps the hot water going in a giant circle.
Taco: We divide these systems into 2 types: “Standard” recirc. lines-with dedicated third lines solely for the purpose of returning water back to the water heater, and “cross-over” or “under-counter” systems-those that use the cold line as the return loop. “Standard” recirc systems, like Taco’s Plumb ‘n’ Plug product line, are common on new construction and easiest to install during the rough-in process. Usually a half-inch line is tee’d into the last fixture of a plumbing system and run back to the water heater. It’s usually connected to another tee at the tank’s drain valve. An alternate method is to tee into the cold water supply to the water heater. The pump is installed on the return line near the water heater with a flow check valve somewhere between the pump discharge and the tank. This prevents gravity flow or thermal siphoning in the backwards direction when the recirc pump is off.
“Cross-over” or “under-counter” systems, like the D'Mand System, are quite different. They utilize the cold line for short periods to return the “cooled” hot water back to the tank. Depending on the manufacturer, this is accomplished in two different ways-Pump under-counter connected to cold line; or, crossover valve under-counter connected to cold line with pump at water heater. The pump is connected to the hot and cold lines at the last fixture in a piping system and is plugged in to a 115-volt power source, which may need to be installed. When activated the pump quickly returns cooled hot water back to the tank and runs only long enough to get hot water to the pump. This usually takes 10-15 seconds max. At that point a temp thermistor detects the sudden increase of water temp and shuts off.
Uponor: There are four main options; three of which use pumps and one does not. The three that use pumps are: 1) continuous recirculation, 2) timed recirculation (with or without an accompanying aquastat), 3) on-demand recirculation. A fourth option, without a pump, relies on gravity or siphoning action.
Of these systems, only on-demand qualifies for points in either LEED-H or ICC 700, although all of the schemes can result in water conservation. In residential applications, continuous recirc. is rarely employed; it is much more common in commercial structures, such as hotels. Recirc. systems are most easily installed in new construction, but retrofit systems are also available.
RJ: About how much annual water savings could a family of four see with the installation of HWR pumps?
Grundfos: Our estimates show more than 12,000 gallons a year.
Laing Thermotech: That depends on a whole lot of variables so it’s difficult to give a definite answer. A while back we had an energy study done with some of our pumps and it depends on what you’re paying for electricity, of course. But the water savings could be up to 12,000 gallons a year.
Taco: Depending on which study you follow, the common estimate is that an average family of four can waste up to 12,000 gallons of water a year just waiting for hot water to arrive at the fixtures. In fact it is hard to calculate because as a culture, we have become pre-conditioned to expect a wait period. So we turn on the shower and walk away for a few minutes to be sure the water is hot. Who knows how much “HOT” water we send down the drain needlessly-not to mention the wasted energy along with it.
Uponor: Savings can vary a lot, depending on family size, house size, plumbing layout and usage patterns. A conservative estimate is that a daily savings of 20 gallons of water is possible. Combined savings for water and energy are estimated to be about $225 per year for an electric water heater and somewhat less for gas.
RJ: What is the best way for a contractor to sell this high-margin system to ‘green’ conscious customers?
Grundfos: Position it as a water savings device by asking, “How long do you wait for hot water for your shower in the morning?” to get them thinking about the time they waste. Then move the conversation to how much water they waste while waiting. Some savvy contractors have used a five-gallon bucket and stopwatch to make the point, too.
Laing Thermotech: If [the customers] are waiting a long time for hot water to arrive and if they’re tired of waiting for it then here’s the answer. And here’s what it’s going to save you-not only money but water as well.
Taco: Our “Domestic Hot Water Recirculation Guide” goes into detail regarding the features and benefits of a recirc system. It can be downloaded as a PDF document from the Web site here.
Uponor: Position it as a feature that provides two types of benefits: First, there is convenience (by virtually eliminating the annoyance of having to wait for hot water to arrive at a tap); and second, you have the water/energy savings. The contractor also should appeal to a homeowner’s sense of doing the right thing by conserving water on behalf of society. Some experts predict that looming water shortages are on the same scale as the effects of global warming.
"This article was originally posted on ww.reevesjournal.com."
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