Estimate amount of water use by application
Troubleshooting your pump
Electrical Help
-Misc
Manufacturers' Links
FAQ
How
do I read
a pump
curve?
How do
centrifugal
pumps
work?
Which type
of tank
should I
use and
how big?
How do I
determine
the energy
consumption
of a pump?
Why should
I care
about
suction
lift?
What is
the
purpose of
a torque
arrestor?
Do I need
a snifter
valve,
bleeder
orifice or
air
release
valve?
Should I
worry
about
below
freezing
temperatures?
Two wire
VS. three
wire
Low yield
wells and
pump
settings
Drop pipe
Small
diameter
and sandy
wells
Why
do
submersible
pumps
fail?
What
is the
best brand
of
submersible
pump?
How
much does
pipe
weigh
Solar
applications
Lake
and pond
installations
5
or 12 GPM
1/2 Hp.
What's the
difference?
HOW TO READ A PUMP CURVE ( with some simplifications)
Imagine that you have a basic water pump with the discharge connected to a short piece of pipe with a pressure gage and a gate valve in it.
Suppose you shut the valve and turn the pump on. The pressure gage will reach some maximum and the flow will be zero since nothing can get past the valve.
If you now open the valve a little bit there will be some flow and the pressure gage reading will drop a bit. As you open the valve more and more the flow increases and the pressure drops.
When the valve is fully open you will get the maximum flow and the pressure will be zero.
If you plot these readings on a graph with flow in gallons per minute on the bottom ( x axis) and pressure measured in feet of water on the left ( y axis) you will have a pump curve.
This curve is determined at the foundry where the impeller is cast and nothing, within reason, will change it. It is used to tell what flow the pump will produce at any given head pressure.
Note that pressure is a measure of resistance to flow. It is the total resistance in a system that determines the flow output of the pump. Without any resistance, the pump delivers its maximum flow. Pumps are quite stupid and totally unaware of what you intend them to do. They deal only in what is real to them and they don't know anything except what is at their suction and what is at their discharge.
Pump curves are customarily marked in feet of head because any liquid pumped will be lifted to the same height. This is true whether it is oil, water or molten lead. ( Pressure and energy required are another thing altogether). For water applications,
( pressure in PSI) = feet x .433 or, ( head in feet) = (pressure in PSI) x 2.31
for example: 60 PSI = 138.6 ft
HOW CENTRIFUGAL PUMPS WORK ( very simplified)
A centrifugal pump is basically a rotating shovel for liquid. Each rotation it expels a donut of liquid. The volume of the donut represents how many gallons per minute the pump delivers.
The liquid is thrown off the vane tips. At the center of the shaft there is no relative motion but the liquid there moves out to replace the liquid thrown off the tip. This creates a low pressure area at the shaft center, which is also the liquid inlet (pump suction). External pressure on the liquid supply, which may only be atmospheric pressure, forces more liquid into the pump suction.
The amount of velocity of the liquid as it leaves the pump determines how much head ( or pressure) the pump will develop. This is determined by the diameter of the vane and how many revolutions per minute it makes (shaft speed). h=V5/2g for you engineers.
Pumps are designed around a flow rate which determines how big the case must be to efficiently handle the quantity of water desired. This is indicated by the inlet and outlet pipe sizes but there can be considerable variation.
If it gets impractical to make an impeller large enough in diameter to get the head desired, two or more impellers ( stages) can be incorporated into one housing. This is very common in water well pumps where the pump must go down a hole. It is very hard to get a pump with a diameter larger than the hole to go in without the use of a hole stretcher. This device is large, dangerous, and illegal in most states. Ask your well driller.
A pump converts the energy used to turn its shaft into water energy. The efficiency with which it does so determines what it costs to move the liquid. It takes the same amount of energy to lift one gallon of water two feet as it does to lift two gallons one foot.
The formula for water is:
Horsepower = (Gallons per minute) x (Total dynamic head in feet)
3960 x pump efficiency
This is derived from the definition of horsepower and is always true. For liquids other than water, the specific gravity must be used but that is for another web page. 3960 is a conversion factor to make the units come out right. The word dynamic means the total head is figured when the liquid is in motion and so friction losses must be included.
The low pressure generated in the suction of a pump will lift water up into the pump. There are some limitations.
The basic limit is atmospheric pressure which is 33.9 feet. No pump can lift water up into it more than 33.9' even if you put a million horsepower motor on it. Once you get the water into the pump you can blast it to the moon if you want to put the energy in, but the suction side is limited. The pump is sucking on a big straw. If you run out of suction power the water will just sit there at what ever point you ran out.
The other limit is the amount of energy each individual pump needs to get the water into its suction area and turn up the blades. This is essentially an internal friction factor and it can get quite large, even much higher than atmospheric pressure. This is called Net Positive Suction Head required, or NPSH. If this requirement is not met, the water will form bubbles of water vapor ( not air). These bubbles will move with the liquid into the higher pressure areas of the pump and instantly collapse. When they do, the liquid around trying to rush into the void at infinite velocities. This erodes metal and makes a sound like pumping rocks. It causes vibrations, loss of capacity and severe impeller wear. It is a very bad thing for a pump.
The third limitation is liquid temperature. The warmer the liquid, the easier it is to go into the vapor phase and thus cavitate more easily. It is impossible to lift water that is boiling.
This is normally only a concern in boiler feed applications and industrial applications.
In a water pressure system a tank is primarily a hydraulic accumulator. Its main function is stop the pump going on and off excessively. Storage of water is secondary.
The tank can only serve its purpose if there is an air pad in the tank which has been compressed by the pump. If there is no air, the tank is just a fat piece of pipe. Pressure in the system drops immediately when any amount of water is used.
There are two basic types:
1. Captive air, or bladder tanks
2. Galvanized or epoxy coated non-bladder tanks
The bladder tanks have a rubber bag inside them which separates the air and water and is pre-pressurized. Since air under pressure dissolves in water, this means you don't have to add air or drain the tank. The pre-pressurizing gives you more useful storage in the same physical space. This makes them cheaper per gallon of draw down than the plain tanks, especially the larger ones. It also means they are lighter and easier to install. However, there are many manufacturers of wildly different quality levels, and all of the bladders will fail sooner or later.
The plain tanks probably have a longer life. They do have to be kept full of air. This can be done with a submersible pump by using an air charging system consisting of a down hole bleeder valve, a surface snifter and an excess air release on the tank. The snifter valves are cheap but prone to plugging.
All plain tanks can be drained and air let into them if you remember too do it. It is necessary to break the vacuum and actually let air in and not just drain the tank from the bottom or a water faucet.
TANK SIZING
The tank
is sized
to the
capacity
of the
pump. The
object is
to limit
the number
of starts
per hour
the pump
makes. The
larger the
motor, the
fewer
starts are
recommended.
Franklin
recommends
up to 300
starts per
day for
1/2 and
3/4 HP
motors,
100 per
day for 1
HP thru 5
HP, and 50
per day
for
anything
up to 30
HP.
Water use
is not
uniform
during the
day. We
feel that
this
formula
can be met
and still
beat the
daylinghts
out of the
motor. Try
to size
the tank
such that
you will
never
exceed 6
starts an
hour. This
means a
cycle time
from start
to start
of 10
minutes.
For
example,
if you
have a
pump with
a 10 GPM
capacity
and a tank
with a
"live
storage"
capacity
of 25
gallons,
and, worst
case, when
the demand
is half
the pump
capacity
or 5 GPM,
it will
take 5
minutes to
fill the
tank and
five
minutes to
empty it,
thus
giving you
a ten
minute
cycle. In
practice,
this can
be
exceeded
occassionally
without
undue
alarm. In
cases
which can
create
prolonged
demand at
half the
pump
capacity,
such as
heat pumps
or poorly
thought
out
irrigation
systems,
It is very
important
to have
adequate
tank
capacity.
Live
storage is
the amout
of water
that you
can draw
out of a
tank
between
the pump
off
pressurte
and the
pump on
pressure.
For
galvanized
tanks this
is about
11% of the
volumne of
the tank.
For
captive
air tanks
the
manufactureer
publishes
the
numbers.
Usually,
the model
number of
the take
is related
to the
live
storage
i.e., a
PC244 has
a live
storage of
24.4
gallons.
It is
never a
problem to
have a
tank that
is too
big. To
quote Mae
West
"
Bigger is
Better!"
Torque arrestors are recommended for installations that use PVC drop pipe for three reasons. The first is that most pumps rotate in a direction that will cause the drop pipe to unscrew. A torque arrestor keeps the pump snug in the well casing reducing the possibility that the pump starting torque will result in any right hand thread loosening. It is attached to the drop pipe right at the pump, then it is expanded until it fits snugly in the well casing.
The second reason a torque arrestor is used is to keep the pump centered in the well. Not all wells are straight, a pump that is running up against the well casing may experience motor cooling problems and hydraulic imbalances. A pump hanging on plastic pipe will tend to move around and collide with the well casing which can result in abrasion to the pump and motor housings, damaged wire or damaged well casing.
The third and most important reason is that fatigue from repeated start-up torque will occur in the PVC and can cause the pipe to break.
DO I NEED A SNIFTER, BLEEDER ORIFICE OF AIR RELEASE VALVE
Air charging systems require an air snifter valve, a bleeder orifice and an air release valve.
An air release valve is required on air charging systems to maintain the correct water to air ratio in the tank. In an air charging system, excessive air is pumped into the tank on each cycle. There are usually two check valves installed in one of these types of systems, one on the pump and one on the surface pipe. When the pump stops, both check valves close. The water in the pipe between the air snifter valve and the orifice plug bleeds back through the orifice and down into the well. When the pump starts again, the air that replaced the water in the pipe between the snifter and bleeder orifice is pushed into the tank.
Excessive air will continue to lower the water level in the tank, as the water level is lowered, the air ejector float is also lowered which opens the release valve and lets excessive air out until the release valve setting is reached. When the pump starts again, the water level rises and raises the air ejector float which closes the releases valve before the water level reaches the valve.
In most domestic pumping systems there is a pressure switch that controls when the pump starts and stops. That pressure switch is typically connected to the system with a pipe nipple. It is important to protect that connecting nipple from freezing because if it does freeze while the pump is running, the switch will never see the system pressure reach the shut off point and therefore will not turn the pump off. Dangerously high pressures can be developed depending on the head a specific pump is capable of achieving. Pressure tanks will detonate if the pressure in them gets too high. An inexpensive way to protect pipes from freezing is with pipe insulation which is usually sold at hardware stores. Burlap or fiberglass insulation are also commonly used surface pipe insulators .
Slightly more than half of all submersibles sold are two wire and Franklin Electric says the failure rates are the same or slightly better for two wire motors.
Local preferences govern, if you choose the type not common in your area all your neighbors will make fun of you.
We will supply either, two wire pumps are easy to install.
LOW YIELD WELLS AND PUMP SETTINGS
Well
water
storage
capacity
in gallons
per foot
of pipe
below the
water
level"
4"
well
casing =
.653
Gal/ft
5"
well
casing =
1.02
Gal/ft
6"
well
casing =
1.47
Gal/ft
8"
well
casing =
2.61
Gal/ft
10"
well
casing =
4.08
Gal/ft
12"
well
casing =
5.84
Gal/ft
A low well is one that produces less water than normal required demand rates. Usually, a well that yields less than 10 GPM is considered low yield although in some poor water areas, that would be a good well.
The difference between immediate needs and well yield is made up by pumping from storage. This can be an above ground non-pressure tank, an above ground pressure tank, or the water in the well casing.
Wells that are just marginally low are most likely to be buffered by pressure tanks. Pressure tanks are more expensive per gallon stored, but you need one anyway, and in a close case it is simpler and cheaper to increase pressure tanks.
In extreme low yield wells, less than 2 GPMs or so, an above ground reservoir of some type is required. Water usage is very spotty. It peaks in morning and evening hours for
washing and cooking. The well gives a sustained 24 hour yield which can be pumped up and stored and used at peak times by means of a booster pump and small pressure tank. A 3/4 HP jet pump and a captive air tank and a check valve so water can’t backflow from the pressure tank to the storage tank are all that is required.
The storage tank can be an above ground steel or poly tank, or a below ground cistern. This system uses smaller submersible pumps since they do not have to develop pressure other than that required to lift the water to the surface plus the top of the tank. A level switch in the tank controls the well pump.
The third method is using the well itself as the storage tank. This works well if the end user understands what is going on. It is also the most common cause of submersible pump mis-applications and consequent short life and excessive costs.
The pump will be designed to work within a flow range and a pressure range. Pumps have an operating range of 200' to 300'. This means that this is all the water you can use without getting out of the range the pump was designed for.
The manufacturers use up all the horsepower available for each condition set. A 5 G.P.M. design pump will not necessarily be suited for a 5 G.P.M. well. The pump will be designed to pump from a deep depth to use up the horsepower. The essential stupidity of the pump prevents you from explaining the situation to it. The water comes up inside the pump to the exact same level as it does outside the pump without the pump running. If the water level is high when the pump starts, as it would be most mornings, the pump may well go into an up thrust condition which shortens the life of the motor and the pump. It is also inefficient from a power standpoint.
A typical case is a 500' well yielding 3 G.P.M. with water standing at 30'. A pump is chosen that can lift water from 500'. This pump runs off it’s performance curve at 200' and so at the 30' startup it up thrusts and pumps inefficiently. In addition, the water flow in the well may all come from above thus reduce the motors ability to cool and shortening it’s life. ( Franklin motors in sizes below 2 HP are able to operate satisfactorily this way but will last longer if cooled with water flow from below.) It is also true that it costs more to pump water the greater the distance you have to lift it to the surface.
All pumps in low yield wells can benefit from protection by a Franklin Pumptec which will shut the pump off if it runs dry. No pump can withstand prolonged running dry without damage.
My conclusion is that the proper way to use the well as a reservoir is to compare the storage capacity of the well in 200' with your expected daily use.( A six inch well stores about 300 gallons in 200'. The average usage of a family of four is 200 gallons per day plus irrigation needs.) Select a pump that will work well in this range and live within these limits. Protect the pump with a Pumptec. The smallest pump that will meet these requirements is the correct pump from installation cost, operating cost ,and durability standpoints.
The
pipe
connecting
the
submersible
pump to
the
surface is
called the
drop pipe.
(Actually
dropping
it is
neither
necessary
nor
desirable.)
It
may be:
Galvanized
steel
PVC
schedule
80
Poly pipe
160 PSI
Poly pipe
200 PSI
PVC
schedule
40
Galvanized
steel:
Heavy,
expensive,
can
corrode in
some
waters.
Holds most
weight and
resists
torque.
Comes in
21'
lengths,
threads
together.
Comes in
sizes to
6".
PVC
schedule
80 with
molded in
threads is
light,
strong,
corrosion
proof and
moderate
in cost.
Comes in
20'
lengths.
Threads
together.
Somewhat
flexible.
Torque
arrestor
required.
Normally
only
available
through
water well
industry.
Limited on
depths and
motor
sizes. Too
expensive
to ship
except in
very large
quantity.
Comes in
1", 1
1/4",
1 ½"
and
2"
sizes. PVC
couplings
made by
the pipe
manufacturer
are
heavier
and
stronger
than
normal sch.
80 and
should be
used.
Maximum
depths and
horsepower
ratings as
follows.
If used at
extreme
ends of
ranges,
install a
safety
rope and
pray.
1"
1.5
HP max
600'
max. Use
metal
couplings
below 300'
1.25"
2
HP max
500'
max. Use
metal
couplings
below 300'
1.5"
5
HP max
400'
max. Use
metal
couplings
below 200'
2"
7.5
HP max
340'
max. Use
metal
couplings
below 200'
Poly
pipe 160
PSI. Comes
in 1"
and 1
1/4"
sizes and
rolls of
300'.
Similar or
slightly
more
expensive
than PVC.
Torque
arrestors
and cable
guides
required.
Special
fittings
top and
bottom
required.
Shippable
but
relatively
expensive.
For use to
pressure
rating at
the pump
discharge
(down the
well).
A
safety
margin of
30% of
rated
pressure
is
recommended
by us with
absolutely
no
scientific
reason for
picking
that
figure.
The
manufacturers
do not
even
acknowledge
that pumps
are a
suitable
use, but
miles of
it are
used.
Safety
ropes are
always
used,
1/4"
nylon or
poly rope
is
adequate.
For larger
pumps
1/8"
stainless
steel
aircraft
cable can
be used
but it is
costly.
Poly
pipe 200
PSI. Same
as above
but comes
also in
100'
rolls. In
1"
size,
available
in 600'
rolls.
PVC
schedule
40. Not
recommended
with glued
joints.
The
couplings
tend to
crack in 5
or 6
years.
Can
be used in
limited
applications
with sch
80
fittings.
It is
usually
not worth
the
minimal
cost
savings to
mess with
it.
Glue
must have
ample time
to set
completely
before
pump
pressure
is applied
or it can
blow
apart.
SMALL
DIAMETER
WELLS AND
SANDY
WELLS
Wells
with an
internal
diameter
of less
than
4"
can not be
used with
standard
submersible
pumps. The
smallest
motor has
a diameter
of
3.75".
Grundfos
makes a
pump for
3"
wells
using
their own
motor. The
only pumps
made for
smaller
than
3"
are from
the
monitoring
well
industry.
They are
very
expensive,
it would
usually be
better to
drill a
proper
well. Jet
pumps can
be used in
many
circumstances
depending
on pumping
levels.
Sandy
Wells
Most well
water has
at least
some sand.
It is a
matter of
degree. If
you
experience
short pump
life, you
have too
much. If
youcan
draw a
glass of
water and
after it
settles,
there is a
dime sized
pile of
sand in
the bottom
of the
glass, you
have a
problem,
if there
are 4 or 5
grains,
you don't
have a
problem.
Obviously,
there is
some
interpertation
required.
The effect
of sand on
humans is
negligable
unless it
covers
your whole
body or
some bully
kicks it
in your
face. Sand
is not
good for
pumps. The
internals
are
plastic.
The pumps
with
stainless
steel
internals
don't do
any
better.
Stainless
steel is
soft.
All pump
manufacturers
take into
consideration
the fact
that their
product
will have
to pump
some sand.
If you
have a
problem
you can:
a) Drill a
new well.
Make a
well
driller
happy! (
There is a
company in
Nigeria
that will
sell you a
water well
in a box
over the
internet.
All they
want is
your bank
account
number.)
b) Install
a Lakos
submersible
centrifugal
separator.
They work.
A bit
expensive.
Pump must
be pulled
to install
it.
Results
may vary
greatly
depending
on the
size of
sand you
have. Does
the well
fill up
with sand?
It should
but it
doesn't
seem to.
c) Cut the
flow rate.
The
greater
the flow
rate of
water, the
greater
the sand.
d) Cut
down the
number of
starts.
Most of
the sand
comes
within a
few
minutes of
pump
starting.
e) Install
of piece
of well
screen
around the
pump. This
means
pulling
the pump.
It also
means you
have to
have at
least a
6"
well.
WHY
DO
SUBMERSIBLE
PUMPS
FAIL?
1.Short
cycling-
going on
and off
too much.
Tank too
small.
2.Pumping
excessive
amounts of
sand.
3.Running
dry.
4.Voltage
spikes-
lightning,
transients.
5.Upthrusting
due to
improper
selection-high
head pumps
in low
head
applications
or
starting
conditions
WHAT
IS THE
BEST BRAND
OF
SUBMERSIBLE
PUMP?
They
all are,
if you ask
them. Most
are good.
The
technology
is well
developed
and too
competitive
for bad
product to
last long.
The
leading
brands
are:
J-Line
Gould
Myers
Aermotor
Red Jacket
Jacuzzi
Flint
&
Walling
Grundfos
Fairbanks
Morse
Sta-Rite
We sell
the first
three and
have
such a low
failure
rate that
we can’t
see any
pattern.
Size
Galvanized
steel
Sch
80 PVC
Weight
of water
in pipe
1"
1.68
lbs/ft
.41
lbs/ft
.31
lbs/ft
1
1/4"
2.28
.57
.53
1
1/2"
2.73
.69
.77
2"
3.68
.96
1.40
2"
Solar
applications
Pumps to
run on
solar
systems
must be
kept
small,
must be
three
wire, are
best
installed
with
capacitor
start-capacitor
run
control
boxes.
This type
control
box costs
more but
reduces
starting
and
running
amps by 10
to 20%.
The solar
system
must have
the surge
capacity
to handle
the
starting
inrush
current of
the motor
which will
be about 6
times the
full load
running
current.
Submersible
pumps are
frequently
installed
in lakes
and ponds
and
rivers.
There are
several
things to
be aware
of if you
want good
life.
a) Solids
- these
pumps are
NOT
designed
to pump
anything
bigger
than a
grain of
sand, this
means no
fish, no
leaves, no
grass, no
insects,
no moss.
None.
b)
Mounting
position.
They can
be used
from
straight
up to
horizontal
and
anywhere
in
between.
However,
they are
designed
to run
straight
up and
this gives
the best
life.
Thrust
bearing
considerations
occur when
installed
at angles.
Starts
must be
reduced to
less than
10 per
day.
c) Motor
cooling.
Water
temperature
must be
below 85
degrees F
for normal
installation.
Franklin
motors
that are
of their
"
Super
Stainless
"
construction
2 HP and
below do
not
require
flow
inducer
sleeves,
however we
recommend
it. The
motor must
never be
embedded
in sand or
laying on
the bottom
or it
can't cool
itself.
d)
Submergence.
The pump
and motor
must be
underwater
at all
times.
e) Floods.
River
installations
are
vulnerable
to being
washed
away or
beaten up
by
debris.
We
recommend
that if
possible
you make
what
amounts to
an
artificial
water well
by
mounting a
piece of 4
or 6"
PVC pipe
vertically
in the
water.
Support
the pump
on a piece
of
galvanized
pipe from
a standard
well seal.
Screen the
bottom of
the pipe
with
something
with holes
smaller
than the
pump inlet
screen,
about
1/8"
holes. If
the water
is
not
crystal
clear, try
to provide
as large a
screen
area as
possible.
Drill
holes in
the side
of the
PVC, below
the motor,
and screen
them also
to provide
more inlet
area. Try
to
support it
from
something
that you
can get to
so it can
be removed
when it
dies.
5 GPM or 12 GPM 1/2 Hp. What's the difference?
What
does it
mean when
you talk
about a 5
G.P.M.
series
pump? Why
can’t I
get a 2
G.P.M.
pump when
that is
all my
well will
produce?
All
manufacturers
start off
with two
design
constraints:
The
impeller
diameter
can’t be
bigger
than
3"
(or it
won’t
fit in a
4"
well),
motors
come in
certain
sizes- ½.
3/4, 1, 1
½ HP,
competitive
pressure
requires
that they
get as
much out
of each
motor as
possible.
The
only
things
they can
control
are the
width of
the
impeller
blades and
the number
of stages.
The wider
the blades
the more
volume in
the
“donut”
of water
each
impeller
puts out
each time
it
revolves.
They pick
blade
widths
that
center on
common
volume
requirements
such as 5,
8, 10, 15,
20. They
then add
stages, to
add lift
(head,
pressure),
until they
use up a
standard
motor
size.
There is a
minimum
blade
width
where
friction
starts to
eat up all
the energy
resulting
in extreme
inefficiency-
therefore
no 2 G.P.M.
pumps.
The
compulsion
to use up
the
horsepower
available
means that
low gallon
range
pumps end
up with
more
stages and
thus high
heads.
This
is great
if water
levels are
deep but
causes
problems
with
relatively
high water
tables.
Pumps,
being
supremely
stupid and
obstinate,
insist
from
pumping
from the
water
level that
is no
matter how
many times
you
explain to
it that it
isn’t
supposed
to. Pumps
are
perpetual
teenagers.
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