Sizing up your sump pump
904-346-1266
Sizing Up your
sump
PUMP
It’s every homeowner’s nightmare—a
basement under water. Carpeting ruined.
Belongings water-logged.
In the ongoing battle for dry basements,
sump pumps play a pivotal role. A pump typically
has to be replaced every few years. But if you
size it correctly, you can extend the life of your
pump. What’s more, you can ensure that you
have the right pump for the job.
When you’re selecting the size of a sump
pump, you need two pieces of information:
•
System Capacity
•
Friction Head)
Total Dynamic Head (Static Head plus
Determine System Capacity
It’s important that your pump can draw water
out of the basin (or “sump pit”) faster than water
flows into it. Therefore, the first thing you need
to measure is the amount of water that drains
into the basin during a high-flow period.
During a heavy rain, stick a ruler in the basin
and measure how many inches of water flow
into the basin in 60 seconds. This will tell you
how many gallons flow into the basin per
minute, which is the System Capacity.
If you have an 18-inch-diameter basin, 1
inch of water is equal to 1 gallon. If you have a
24-inch-diameter basin, 1 inch of water is
roughly equal to 2 gallons.
If you find out that more than 30 gallons of
rainwater flow into the basin per minute, you’re
better off with a 24-inch-diameter basin. Also,
the water level should never be allowed to go
higher than the bottom of the inlet pipe of the
foundation drain tile.
But what if you’re building a new home and
don’t have a system installed yet? In that case,
there are some general guidelines.
If you’re building on sandy soil, plan for a
system capacity of 14 gallons per minute for
every 1,000 square feet of home.
If you’re building on clay soil, plan for a
system capacity of 8 gallons per minute for
every 1,000 square feet of home.
Example:
inches of water flow into your sump pump basin
in 60 seconds. Because you have the smaller
diameter basin, each inch equals 1 gallon.
Therefore, your System Capacity is 18 gallons
per minute.
Using a ruler, you find that 18
Determine Static Head
Total Dynamic Head is equal to Static Head
(or “vertical lift”) plus Friction Head.
Static Head is the vertical height that the
water rises through the discharge pipe. Begin
measuring from the point where water enters
the sump pump. Then measure up vertically
to where the pipe becomes horizontal (see
Figure 1).
Example:
sump pump to the point where the discharge
pipe becomes horizontal is 13 feet. This is the
Static Head.
Assume that the height from the
2
Determine Friction Head
Determining Friction Head is more involved
than finding out the Static Head. Friction Head is
“the equivalent length of pipe” plus the actual
length of pipe multiplied by the “friction loss”
divided by 100.
What follows are four steps in figuring out
Friction Head.
Step 1. Determine Equivalent Length
of Pipe
The equivalent length of pipe is determined
by how many pipe fittings are required for your
system. Table 1 shows the equivalent length of
pipe for various fittings, based on pipe size.
Example:
pipe, with three 90-degree elbows and 1 check
valve. According to Table 1, three elbows add
10.5 feet of equivalent pipe, while the check
valve adds 11.5 feet. The total equivalent feet
Assume you’re using 1¼-inch
Step 2. Determine the Actual Pipe Length
The actual pipe length is the length of pipe
running horizontally out of the house. You should
be able to see where the pipe discharges
outside of the house.
Example:
discharge pipe is 100 feet.
In our example, the length of
Step 3. Determine Friction Loss
Friction loss is how much friction slows the
flow of water moving through the pipe. Table 2
shows what friction loss occurs for different
pipe sizes, depending on how many gallons of
water per minute move through the pipe.
With Table 2, use your System Capacity
number as the “gallons per minute.”
Example:
through your 1¼-inch pipe, it would create a
friction loss of 5.25 per 100 feet of pipe.
If 18 gallons per minute flow
Figure 1. A Sump Pump System
The Sump Pump
of pipe is 22 feet.
3
Step 4. Put it All Together
To figure out Friction Head, add the actual
length of the discharge pipe to the equivalent
length of pipe from fittings
friction loss and divide by 100.
. Then multiply by the
Example:
discharge pipe (100 feet) with the equivalent
length of pipe from fittings (22 feet) to get 122
feet. Then multiply this by the friction loss per
100 feet of pipe (5.25) and divide by 100.
122 x 5.25
6.40 is the Friction Head
Add the actual length of the÷ 100 = 6.40 feet
Determining Total Dynamic Head
Now that we’ve determined Static Head and
Friction Head, we simply add the numbers to
get Total Dynamic Head.
Example:
the Friction Head (6.40) to get a Total Dynamic
Head of 19.40. Round up to 20 feet.
Add the Static Head (13 feet) to
Selecting the Pump
You now know your System Capacity (18
gallons per minute) and you know the Total
Dynamic Head (20 feet). So you’re ready to
select a pump.
Most sump pumps have charts or curves
that show how many gallons per minute they
can pump for different lengths of head (See
Figure 2). You’ve already determined how
many gallons per minute must be pumped out.
So look at these charts and make sure that the
pump can handle that many gallons per
minute.
You don’t want a pump that is either too
small or too powerful. If the pump is too small,
it won’t be able to keep up with water flowing
Table 1. Equivalent Length of Pipe
Due to Fittings
Table 2. Friction Loss Per 100 Feet of
Plastic Schedule 40 Pipe
Figure 2. Sample Sump Pump Performance Curves
4
August 2005
into the basin. If the pump is too powerful, it will
“short cycle.” This means the pump will start
and stop frequently, which can cause premature
pump failure.
Example:
feet, you have only one choice among the four
pumps shown in Figure 2. Only Pump 1 will be
able to handle 18 gallons per minute. The other
three pumps can’t handle any more than 12
gallons per minute.
Note that changing to a larger size of pipe in
this case might lower the friction head enough
to enable you to use a different pump (Pump 2
on the chart).
If the Total Dynamic Head is 20
Maintaining the Pump
Periodically maintain your pump by doing the
following:
•
sure that its up-and-down movement is not
restricted.
Check the operation of the float to make
•
running to make sure it is discharging water.
Several things can cause water not to be
discharged, including a stuck check valve,
the impeller loose on its shaft, or a plugged
water pipe.
Check the outside pipe when the pump is
•
months, put enough water in the sump
pump basin to trigger the float switch. That
way, you ensure that the pump is still operating
If the pump has not had to run for several months
It’s every homeowner’s nightmare—a
basement under water. Carpeting ruined.
Belongings water-logged.
In the ongoing battle for dry basements,
sump pumps play a pivotal role. A pump typically
has to be replaced every few years. But if you
size it correctly, you can extend the life of your
pump. What’s more, you can ensure that you
have the right pump for the job.
When you’re selecting the size of a sump
pump, you need two pieces of information:
•
System Capacity
•
Friction Head)
Total Dynamic Head (Static Head plus
Determine System Capacity
It’s important that your pump can draw water
out of the basin (or “sump pit”) faster than water
flows into it. Therefore, the first thing you need
to measure is the amount of water that drains
into the basin during a high-flow period.
During a heavy rain, stick a ruler in the basin
and measure how many inches of water flow
into the basin in 60 seconds. This will tell you
how many gallons flow into the basin per
minute, which is the System Capacity.
If you have an 18-inch-diameter basin, 1
inch of water is equal to 1 gallon. If you have a
24-inch-diameter basin, 1 inch of water is
roughly equal to 2 gallons.
If you find out that more than 30 gallons of
rainwater flow into the basin per minute, you’re
better off with a 24-inch-diameter basin. Also,
the water level should never be allowed to go
higher than the bottom of the inlet pipe of the
foundation drain tile.
But what if you’re building a new home and
don’t have a system installed yet? In that case,
there are some general guidelines.
If you’re building on sandy soil, plan for a
system capacity of 14 gallons per minute for
every 1,000 square feet of home.
If you’re building on clay soil, plan for a
system capacity of 8 gallons per minute for
every 1,000 square feet of home.
Example:
inches of water flow into your sump pump basin
in 60 seconds. Because you have the smaller
diameter basin, each inch equals 1 gallon.
Therefore, your System Capacity is 18 gallons
per minute.
Using a ruler, you find that 18
Determine Static Head
Total Dynamic Head is equal to Static Head
(or “vertical lift”) plus Friction Head.
Static Head is the vertical height that the
water rises through the discharge pipe. Begin
measuring from the point where water enters
the sump pump. Then measure up vertically
to where the pipe becomes horizontal (see
Figure 1).
Example:
sump pump to the point where the discharge
pipe becomes horizontal is 13 feet. This is the
Static Head.
Assume that the height from the
2
Determine Friction Head
Determining Friction Head is more involved
than finding out the Static Head. Friction Head is
“the equivalent length of pipe” plus the actual
length of pipe multiplied by the “friction loss”
divided by 100.
What follows are four steps in figuring out
Friction Head.
Step 1. Determine Equivalent Length
of Pipe
The equivalent length of pipe is determined
by how many pipe fittings are required for your
system. Table 1 shows the equivalent length of
pipe for various fittings, based on pipe size.
Example:
pipe, with three 90-degree elbows and 1 check
valve. According to Table 1, three elbows add
10.5 feet of equivalent pipe, while the check
valve adds 11.5 feet. The total equivalent feet
Assume you’re using 1¼-inch
Step 2. Determine the Actual Pipe Length
The actual pipe length is the length of pipe
running horizontally out of the house. You should
be able to see where the pipe discharges
outside of the house.
Example:
discharge pipe is 100 feet.
In our example, the length of
Step 3. Determine Friction Loss
Friction loss is how much friction slows the
flow of water moving through the pipe. Table 2
shows what friction loss occurs for different
pipe sizes, depending on how many gallons of
water per minute move through the pipe.
With Table 2, use your System Capacity
number as the “gallons per minute.”
Example:
through your 1¼-inch pipe, it would create a
friction loss of 5.25 per 100 feet of pipe.
If 18 gallons per minute flow
Figure 1. A Sump Pump System
The Sump Pump
of pipe is 22 feet.
3
Step 4. Put it All Together
To figure out Friction Head, add the actual
length of the discharge pipe to the equivalent
length of pipe from fittings
friction loss and divide by 100.
. Then multiply by the
Example:
discharge pipe (100 feet) with the equivalent
length of pipe from fittings (22 feet) to get 122
feet. Then multiply this by the friction loss per
100 feet of pipe (5.25) and divide by 100.
122 x 5.25
6.40 is the Friction Head
Add the actual length of the÷ 100 = 6.40 feet
Determining Total Dynamic Head
Now that we’ve determined Static Head and
Friction Head, we simply add the numbers to
get Total Dynamic Head.
Example:
the Friction Head (6.40) to get a Total Dynamic
Head of 19.40. Round up to 20 feet.
Add the Static Head (13 feet) to
Selecting the Pump
You now know your System Capacity (18
gallons per minute) and you know the Total
Dynamic Head (20 feet). So you’re ready to
select a pump.
Most sump pumps have charts or curves
that show how many gallons per minute they
can pump for different lengths of head (See
Figure 2). You’ve already determined how
many gallons per minute must be pumped out.
So look at these charts and make sure that the
pump can handle that many gallons per
minute.
You don’t want a pump that is either too
small or too powerful. If the pump is too small,
it won’t be able to keep up with water flowing
Table 1. Equivalent Length of Pipe
Due to Fittings
Table 2. Friction Loss Per 100 Feet of
Plastic Schedule 40 Pipe
Figure 2. Sample Sump Pump Performance Curves
4
August 2005
into the basin. If the pump is too powerful, it will
“short cycle.” This means the pump will start
and stop frequently, which can cause premature
pump failure.
Example:
feet, you have only one choice among the four
pumps shown in Figure 2. Only Pump 1 will be
able to handle 18 gallons per minute. The other
three pumps can’t handle any more than 12
gallons per minute.
Note that changing to a larger size of pipe in
this case might lower the friction head enough
to enable you to use a different pump (Pump 2
on the chart).
If the Total Dynamic Head is 20
Maintaining the Pump
Periodically maintain your pump by doing the
following:
•
sure that its up-and-down movement is not
restricted.
Check the operation of the float to make
•
running to make sure it is discharging water.
Several things can cause water not to be
discharged, including a stuck check valve,
the impeller loose on its shaft, or a plugged
water pipe.
Check the outside pipe when the pump is
•
months, put enough water in the sump
pump basin to trigger the float switch. That
way, you ensure that the pump is still operating
If the pump has not had to run for several months
It’s every homeowner’s nightmare—a
basement under water. Carpeting ruined.
Belongings water-logged.
In the ongoing battle for dry basements,
sump pumps play a pivotal role. A pump typically
has to be replaced every few years. But if you
size it correctly, you can extend the life of your
pump. What’s more, you can ensure that you
have the right pump for the job.
When you’re selecting the size of a sump
pump, you need two pieces of information:
•
System Capacity
•
Friction Head)
Total Dynamic Head (Static Head plus
Determine System Capacity
It’s important that your pump can draw water
out of the basin (or “sump pit”) faster than water
flows into it. Therefore, the first thing you need
to measure is the amount of water that drains
into the basin during a high-flow period.
During a heavy rain, stick a ruler in the basin
and measure how many inches of water flow
into the basin in 60 seconds. This will tell you
how many gallons flow into the basin per
minute, which is the System Capacity.
If you have an 18-inch-diameter basin, 1
inch of water is equal to 1 gallon. If you have a
24-inch-diameter basin, 1 inch of water is
roughly equal to 2 gallons.
If you find out that more than 30 gallons of
rainwater flow into the basin per minute, you’re
better off with a 24-inch-diameter basin. Also,
the water level should never be allowed to go
higher than the bottom of the inlet pipe of the
foundation drain tile.
But what if you’re building a new home and
don’t have a system installed yet? In that case,
there are some general guidelines.
If you’re building on sandy soil, plan for a
system capacity of 14 gallons per minute for
every 1,000 square feet of home.
If you’re building on clay soil, plan for a
system capacity of 8 gallons per minute for
every 1,000 square feet of home.
Example:
inches of water flow into your sump pump basin
in 60 seconds. Because you have the smaller
diameter basin, each inch equals 1 gallon.
Therefore, your System Capacity is 18 gallons
per minute.
Using a ruler, you find that 18
Determine Static Head
Total Dynamic Head is equal to Static Head
(or “vertical lift”) plus Friction Head.
Static Head is the vertical height that the
water rises through the discharge pipe. Begin
measuring from the point where water enters
the sump pump. Then measure up vertically
to where the pipe becomes horizontal (see
Figure 1).
Example:
sump pump to the point where the discharge
pipe becomes horizontal is 13 feet. This is the
Static Head.
Assume that the height from the
2
Determine Friction Head
Determining Friction Head is more involved
than finding out the Static Head. Friction Head is
“the equivalent length of pipe” plus the actual
length of pipe multiplied by the “friction loss”
divided by 100.
What follows are four steps in figuring out
Friction Head.
Step 1. Determine Equivalent Length
of Pipe
The equivalent length of pipe is determined
by how many pipe fittings are required for your
system. Table 1 shows the equivalent length of
pipe for various fittings, based on pipe size.
Example:
pipe, with three 90-degree elbows and 1 check
valve. According to Table 1, three elbows add
10.5 feet of equivalent pipe, while the check
valve adds 11.5 feet. The total equivalent feet
Assume you’re using 1¼-inch
Step 2. Determine the Actual Pipe Length
The actual pipe length is the length of pipe
running horizontally out of the house. You should
be able to see where the pipe discharges
outside of the house.
Example:
discharge pipe is 100 feet.
In our example, the length of
Step 3. Determine Friction Loss
Friction loss is how much friction slows the
flow of water moving through the pipe. Table 2
shows what friction loss occurs for different
pipe sizes, depending on how many gallons of
water per minute move through the pipe.
With Table 2, use your System Capacity
number as the “gallons per minute.”
Example:
through your 1¼-inch pipe, it would create a
friction loss of 5.25 per 100 feet of pipe.
If 18 gallons per minute flow
Figure 1. A Sump Pump System
The Sump Pump
of pipe is 22 feet.
3
Step 4. Put it All Together
To figure out Friction Head, add the actual
length of the discharge pipe to the equivalent
length of pipe from fittings
friction loss and divide by 100.
. Then multiply by the
Example:
discharge pipe (100 feet) with the equivalent
length of pipe from fittings (22 feet) to get 122
feet. Then multiply this by the friction loss per
100 feet of pipe (5.25) and divide by 100.
122 x 5.25
6.40 is the Friction Head
Add the actual length of the÷ 100 = 6.40 feet
Determining Total Dynamic Head
Now that we’ve determined Static Head and
Friction Head, we simply add the numbers to
get Total Dynamic Head.
Example:
the Friction Head (6.40) to get a Total Dynamic
Head of 19.40. Round up to 20 feet.
Add the Static Head (13 feet) to
Selecting the Pump
You now know your System Capacity (18
gallons per minute) and you know the Total
Dynamic Head (20 feet). So you’re ready to
select a pump.
Most sump pumps have charts or curves
that show how many gallons per minute they
can pump for different lengths of head (See
Figure 2). You’ve already determined how
many gallons per minute must be pumped out.
So look at these charts and make sure that the
pump can handle that many gallons per
minute.
You don’t want a pump that is either too
small or too powerful. If the pump is too small,
it won’t be able to keep up with water flowing
Table 1. Equivalent Length of Pipe
Due to Fittings
Table 2. Friction Loss Per 100 Feet of
Plastic Schedule 40 Pipe
Figure 2. Sample Sump Pump Performance Curves
4
August 2005
into the basin. If the pump is too powerful, it will
“short cycle.” This means the pump will start
and stop frequently, which can cause premature
pump failure.
Example:
feet, you have only one choice among the four
pumps shown in Figure 2. Only Pump 1 will be
able to handle 18 gallons per minute. The other
three pumps can’t handle any more than 12
gallons per minute.
Note that changing to a larger size of pipe in
this case might lower the friction head enough
to enable you to use a different pump (Pump 2
on the chart).
If the Total Dynamic Head is 20
Maintaining the Pump
Periodically maintain your pump by doing the
following:
•
sure that its up-and-down movement is not
restricted.
Check the operation of the float to make
•
running to make sure it is discharging water.
Several things can cause water not to be
discharged, including a stuck check valve,
the impeller loose on its shaft, or a plugged
water pipe.
Check the outside pipe when the pump is
•
months, put enough water in the sump
pump basin to trigger the float switch. That
way, you ensure that the pump is still operating
If the pump has not had to run for several months