I wonder if you know some little-understood details about your
water heater, that have drastic effects on the efficiency.
Those same details may indicate your water heater is trying to kill you
or perhaps, vice versa, you are trying to kill it.
Too high a pressure inside the tank and you may well be trying to end the
life of your water heater, likewise that same pressure may be the end of
you. Water heaters are required to have a "pressure relief" valve,
which is usually preset to 150 lb./sq.in. If you don't know, 150 lb./sq.in.
is a lot of pressure! That's 150 pounds of pressure
mashing on each square inch! A pair of size 9 men's shoes totals around 80
square inches, and if a man stood on an 80 square inch plate with
150 lbs per sq in pressure on the other side, it could lift a man weighing
12,000 lb. (80 X 150 = 12,000)
Well, that's not too realistic, let's just use one foot and say
a 40 sq. in. plate could lift a 6000 lb. man standing on one foot.
Hmmm, these examples are too difficult to visualize.
A typical car tire has at least 20 sq. in. of rubber on the ground, so
150 lb. of pressure beneath four tires, equally pushing upwards, could lift
a 3000 lb. car! ...a 3000 lb. car, with 3 other 3000 lb. cars on top
OK, now we're talking! You can begin to see what force could be lurking
inside your water heater tank! And consider the SIZE of the outside of
that tank, then remember
150 lb. would be pressing outward on every square inch!
But, because your water system has a "pressure reducer" that reduces
the street water pressure down to a comfortable 40 lb./sq. in. or so, you
don't have to worry near as much about your water heater! Or is your reducer
set very high? Or don't you have one?
Gauges for checking water pressure cost from about $3 to $8 and they screw
onto a standard hose fitting, like those on your washing machine. Not one
device in your house likes high water pressure - not the water
heater, the dishwasher, the clothes washer, nor any of the faucets.
Everything is unnecessarily stressed and will need replacement sooner if
you force high pressure on them .
Well, except for your lawn sprinkler. With super high pressure, you can
water a lawn two houses away.
... With super high pressure, you can water a lawn two houses away.
Realistically, your street water pressure is not likely to be more than
about 60-100 lb./sq. in. Then why are we worried about the pressure in
your water tank
getting to 150? Because the water can get trapped in your house pipes! More
and more municipalities require a "backflow preventer" in your water
supply line. It prevents nasty water from being sucked out of your
house and flowing into your neighbor's for them to drink. That's why
all underground lawn sprinkler systems must have a backflow
preventer. Should the street water pressure dip while the sprinklers are on,
it could suck that water back into your house.
...car radiators and casseroles in the oven...
With backflow devices, the water can get into your house, but can't go back.
Surely you are familiar with the concept of things expanding when they are
heated - that's why car radiators and casseroles in the oven boil over.
Likewise, as your water heater raises the temperature of the incoming
water, it increases the pressure above normal.
After taking a nice long shower, you might need to reheat 1/2 to 3/4 a
tank full - all of that water will try to increase about 3% in volume,
but there's no where for it to go, so it increases the water pressure
until someone opens a
faucet, the dishwasher starts, or perhaps the refrigerator's ice maker
cycles. Of course, that higher pressure may be captured for a while, should
you immediately leave for work or go on vacation.
Do you remember those hoses connecting your washing machine to your
water supply? Whether you wash any clothes or not, those hoses constantly
withstand the full house water pressure. The inexpensive ones are made
of rubber - think of using flexible rubber pipes in other parts of your
house! Are you really comfortable leaving your house alone with those
rubber pipes lurking near your washer? Imagine someone standing near
your washer, with a garden hose, spraying full force against the ceiling!
Or, have you replaced the rubber hoses with the steel-braided type that
very seldom develop a leak, and never develop the catastrophic leaks the
rubber ones eventually do?
We barely mentioned temperature, and that's the major purpose of a
water heater, changing the temperature of water. Each water heater has
a temperature dial, but it's seldom marked in degrees - usually it has
arbitrary numbers, like 1 to 5, or "W" to "H" in several marks. Some
years back if you had a dishwasher, they suggested setting your water
temperature to about 130° F., or higher. Naturally,
the lower the setting, the more energy you save - remember, the water
heater must keep all that water at whatever temperature you select,
ALL the time. Recent dishwashers include a self-contained
booster heater, that operates only when washing dishes, and that lets
the home water heater operate at a lower temperature.
In addition to saving energy all year long, the lower water
temperature is safer - much less chance of someone being scalded by
...it can explode - but under very strange circumstances!!
I wonder if you know what happens if the thermostat behind the
temperature dial fails, and turns on all the time? Your water temperature
will continue to increase, the pressure will continue to increase.
If nothing intervenes, it can explode - but under very
The intervening safety device is the same pressure regulator mentioned above.
It has two functions, it releases the water if the pressure exceeds
150 lb./sq.in. as mentioned above, AND it
also releases if the temperature exceeds 210° F. This temperature
is very important. It's just under boiling and is certainly not
to protect you from being scalded!! 130° F water can scald you.
It prevents a terrible explosion. NO, I don't mean like a water balloon
with steaming hot water inside, that makes you jump. I mean like a stick
of dynamite that makes houses in the neighborhood jump!
If the water were allowed to exceed 212° F. (boiling), the pressure
inside the tank would keep if from boiling, so the temperature could keep
rising. At some point, both the excessive temperature and pressure
would cause the tank to crack and begin to leak. Immediately
as the first trickle of water escapes, the tank's pressure is relieved,
the pressure drops, and that lower
pressure suddenly allows this super-heated water (water that is heated
above the boiling point) to suddenly boil, or, more correctly, flash
Suddenly converting 40 gallons of water to steam releases more power
than a pound of nitroglycerin!! Such power makes 'ex-houses' and
'ex-neighbors'. That's why the pressure regulator and
temperature release valve is required on all water heaters.
You should hope your neighbor has one! - one that works!
Your water heater manual tells you to periodically test your relief valve
by gently lifting up on the handle to release some water, perhaps once
every couple of months. This is an excellent suggestion if your heater
is not too old, otherwise it may become an adventure. After many years
without testing, debris may build up around the inside of the valve and
after you open the value, some of the debris may not let the valve fully
close when you release it. It becomes a difficult decision on an old
water heater, if your valve will not fully re-close, you'll need to
replace it, on the other hand, an old valve may be too corroded to
operate and may not properly release when needed.