The following article is courtesy of HouseMaster Home Inspection.
Does this happen to you? Just as you're enjoying a nice, warm shower, a blast of icy cold water from the showerhead sends shivers down your spine. Or worse, somebody flushes a toilet elsewhere in the house, momentarily sending very hot water from the showerhead. Hopefully you’re able to safely back away; if not, there is a potential for a burn.
While scalding is the most obvious consequence when skin is contacted very hot water, a second often disregarded consequence called thermal shock is the body’s involuntary reflex to recoil from abrupt temperature changes. You might be momentarily sparred from being seriously burned if you can move out of the stream of scalding water quickly enough, but such a quick and involuntary reaction in the wet and soapy confines of a shower area can result in an injurious fall - in addition to being burned. Children and older or physically challenged individuals are at increased risk from fall injuries and burns due to slower reaction times and skin that is more vulnerable to scald burns from hot water.
The cause of this temperature fluctuation is a basic issue of supply and demand. When a toilet is flushed, cold water immediately begins to flow into the tank to refill it, causing the water pressure in the cold-water pipes to dip. If this happens when someone is showering, the amount of cold water available for the showerhead temporarily drops, changing the previously set mixture of hot and cold water to hot only.
A similar condition happens when a hot-water faucet is opened elsewhere in the house but in this case the hot water volume to the showerhead can drop, causing the water to momentarily turn cold. This problem is more evident in plumbing systems that are undersized or old and clogged with mineral deposits. An energy-saving showerhead designed to reduce water flow can exacerbate the problem.
The way to eliminate these potentially hazardous temperature shifts is to install a pressure balanced anti-scald valve or thermostatic temperature control valve in the shower wall where the shower controls are located. A pressure-balanced shower valve is designed to compensate for changes in water pressure.
Though it may look like any other shower or tub valve from the outside, it has a special diaphragm or piston mechanism inside that moves with a change in water pressure to immediately balance the pressure of the hot and cold-water flow. These valves are designed to keep water temperature constant, within plus or minus 2° to 3° F, but do so by reducing water flow through either the hot or cold supply. Most reduce the water flow to a trickle if the cold water supply fails. A thermostatic valve may temporarily shut-off the flow altogether.
Most existing bathtub/showers can be retrofit with a new anti-scald valve; however the cost and labor involved will depend on the type valve currently present, accessibility to the plumbing, and the type of tile or other surface finishes present. If a proposed price appears high, consider that there may be other types or brands of anti-scald valves that offer a more reasonable alternative for your particular situation.
Note: These tips are only general guidelines. Since each situation is different, contact a professional if you have questions about a specific issue. More home safety and maintenance information is available online at www.housemaster.com.
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this happen to you? Just as you're enjoying a nice, warm shower, a blast of icy cold water from the showerhead sends shivers down your spine. Or worse, somebody flushes a toilet elsewhere in the house, momentarily sending very hot water from the showerhead. Hopefully you’re able to safely back away; if not, there is a potential for a burn.