## 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**