In your June issue, plumbing contractor Dave Yates makes a
comment I find very hard to believe (Q&A, 6/06). He
states, "Estimates of the number of deaths from potable
hot-water system bacterial infections range widely, but 10,000
per year is the middle ground."
The article does not state whether 10,000 per year is an
estimate for the United States or for the entire world, but
either way, this number seems unbelievably high to me. Please
elaborate if you have any more information on the
Dave Yates responds: Actually, I suspect that the
number is low, but others who look at the same data might
arrive at a different conclusion. My estimate is based mostly
on statistics concerning legionellosis, or Legionnaires'
disease (LD), a pneumonialike illness caused when water
droplets containing legionella bacteria are inhaled or
In the United States, fewer than 2,000 official cases of LD
are reported each year, but the national Centers for Disease
Control and Prevention estimates that between 8,000 and 18,000
Americans are infected with the disease annually. Many more
cases, CDC scientists say, are not reported or are
misdiagnosed. For example, some researchers believe that
anywhere from 2 percent to 15 percent of the 600,000 patients
who enter hospitals each year with community-acquired pneumonia
actually have LD.
Estimates of LD's mortality rates range from 5 percent to 30
percent. The elderly and people with weakened immune systems
are most vulnerable. So if there are 80,000 or 90,000 cases of
LD per year — and I've included patients misdiagnosed
with community-acquired pneumonia in that number —
there could be as many as 16,000 to 18,000 Americans dying of
the disease every year, based on a 20 percent mortality
How many of those cases are caused specifically by
hot-water-system bacteria? That's hard to say with certainty.
Legionella bacteria are quite common (in low culture numbers)
within both municipal and private potable water systems. Most
outbreaks have been traced to water systems, which can deliver
bacteria to such amplifiers as cooling towers, humidifiers, and
even supermarket vegetable misters. And research has shown that
a hot-water system set at 120°F (rather than
140°F) can provide the perfect environment for
My own investigation into this problem leads me to believe
that potable water systems — and hot-water tanks and
their associated plumbing in particular — are the
primary cause of these infections. Whether we're talking about
hospitals, nursing homes, hotels, or residences, it just makes
sense to reduce the risk by turning up the heat in hot-water
storage tanks to 140°F — and then to protect
end users with mixing valves and antiscald faucets.
Should Have Known
As a new subscriber, I noticed in my first issue a review of
the new Bosch impact driver (Toolbox, 5/06). The author begins,
"I like to think that I keep up with building trends and new
tools, so I was surprised to find a whole new category of power
tools that I was completely unaware of: cordless impact
Exactly where has this gentleman been plying his trade that
these little gems have somehow escaped his notice for at least
the last three years? Outer Mongolia? This is not the sort of
thing that instills confidence in the readership of your
I want to set the record straight about the purpose of the
NAHB Residential Construction Performance Guidelines (In the
The publication enjoys great success in the marketplace, which
indicates that both homeowners and the industry find it very
useful. It was created by a panel of more than 300 builders and
remodelers with input from trade associations and insured
warranty providers, among others.
The guidelines are a tool for evaluating
residential-construction contract performance when there are
questions about what constitutes acceptable practice.
Contractors often refer to these guidelines in their contracts
to establish mutually agreed-upon criteria for resolving
warranty issues and to allow for less contentious dispute
The guidelines are an excellent resource, but they do not
supersede building codes and local regulations, nor do they
replace manufacturers' installation instructions.
Jerry Howard, CEO
Preventive Maintenance: No More Sewer
A couple of years ago, a group of like-minded remodeling
companies began to meet monthly to share our trials and
tribulations and to learn from each other.
Recent discussions turned to plumbing blockage on a large
project where the clients had moved out for a couple of months.
The group experience was that there was often a problem with
sewer backups after clients moved back into a house.
Our conjecture is that old debris in the pipes stayed soft
with constant use, but once the family moved out the gunk had
the opportunity to harden. It then caused problems when the
family resumed residence.
Several of us now routinely snake the drains before clients
move back in.Mark Scott