Domestic Hot Water: A Better Option?

March 4, 2013

The supply of hot water -- and the time in which it is delivered – makes an efficiently designed domestic hot water system paramount in a hospital. And that makes thermostatically controlled hot water flow control valves just what the doctors ordered. Unfortunately, these valves aren’t used as often as they should.

The facts are frightening – especially since the problem can be avoided.

Consider this: As many as one in 10 patients hospitalized in the U.S. contracts an infection, according to the Wall Street Journal. That means nearly 2 million patients annually are infected by bacterium or other agents.

The end result?

The cost is nearly 100,000 deaths and $6.5 billion in overall losses.

Hand washing is a long-standing means of fighting such infections. Doctors, nurses and other hospital employees, as well as patients and guests, constantly wash their hands typically using hot water to do so.

The supply of hot water -- and the time in which it is delivered – makes an efficiently designed domestic hot water system paramount in a hospital. And that makes thermostatically controlled hot water flow control valves just what the doctors ordered. Unfortunately, these valves aren’t used as often as they should.

Normally, a domestic hot water system is manually balanced. Enough hot water flows at a rate to insure that when a faucet is turned on, heated water is quickly delivered at a specified temperature set point - often 120 degrees Fahrenheit. To achieve this, the system is balanced with manually operated valves opened to produce the desired flow rate.

With multiple end points at sinks and showers, balancing usually requires two or more plumbing contractors. They must spend significant amounts of time between the hot water supply and the loop that services a particular bank of sinks or other fixtures, tweaking flow rates until the desired temperature is delivered.

A better method of achieving hot water balancing while using a fraction of the labor is to use a thermostatically controlled valve that opens and closes mechanically based on a temperature set point. For a hospital, this design has many advantages.

One major advantage is the cost reduction realized from the reduced flow. Using a thermostatically controlled valve only requires hot water flow when the temperature drops -- not the constant flow that a manually balanced system needs. 

In a manually balanced system, constant flow requires an engineer-specified pump of sufficient capacity to achieve the desired temperature setting. Such a pump will be driven by a powerful electric motor.

Unfortunately, a larger pump and motor combination is more expensive; because of the higher flow that must be maintained, they wear more quickly and wear out faster. More constant recirculating flow means more wear and tear on piping, pumps, valves and fittings -- and ultimately higher costs. This is particularly true at healthcare facilities, which generally have more hot water fixtures than other buildings.

In addition, the larger pumping motor results in higher energy consumption.

Another cost of a manually balanced system is added maintenance due to erosion.  A constant and greater flow for maintaining a required hot water temperature leads to fluid wearing the piping’s insides. Fluid flow encounters certain spots of turbulent flow around bends and changes in direction that gradually wear the piping’s internal walls. Over time, the piping or its fittings or joints may leak, requiring replacement.

Such an occurrence not only would be hazardous to patients and personnel, but could mean that hospital rooms and facilities are taken out of operation. That’s something no hospital can afford.

A better option is a modestly priced stainless steel control valve that uses a temperature sensor installed at the end points of hot water supply systems.

This inline fitting thermostatically controls a temperature set point in the 110-120-degree Fahrenheit range. The thermostatic actuator expands or contracts and controls hot water flow in the domestic hot water system’s branches, thereby modulating flow to the individual end points.

Instead of using constant high flow to control the availability of hot water on demand, it uses temperature, consequently requiring much less work and demand by the hot water system. And note that this fitting’s stainless steel construction should last longer because it is highly corrosion resistant.

Another factor in favor of thermostatically controlled domestic hot water balancing valves is water conservation. According to the U.S. Department of Energy (DOE), healthcare systems are among a community’s largest water consumers.

Consumption, however, varies greatly -- water use per capita ranges from 40 to 350 gallons per day. And the DOE cites a Massachusetts Water Resources Authority study that concluded that sanitary usage by a hospital is by far its largest category of water consumption, guzzling 42 percent of all water. The DOE advised that "hospitals can realize significant savings by upgrading toilet, shower and faucet technologies."

For a patient, employee or patron who turns on a shower or sink and waits for hot water, what happens to the water that runs out cold? It usually is wasted. The shorter this takes, the less waste.

Thermostatically controlled recirculating valves are used by many demanding facilities, such as stadiums, hospitals and hotels, where maintenance budgets are always under scrutiny, and the availability of hot water on demand is important.

Other facilities should join the movement toward thermostatically controlled recirculating valves.

Nick Tallos is the vice president of engineering for Therm-Omega-Tech

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