A rn* United States

Environmental Protection
Mm Agency

Use of the US EPA Hydrant Sampler

Background and Objective: The hydrant sampler was developed to enable system operators to sample water quality from a desired area of the
distribution system, without accessing a residential or commercial tap, Additionally this approach also allows system operators to quickly assess water
quality in the distribution system in the proximity of a routine compliance sample location.

Dry barrel hydrants are the most common type of hydrant. They are designed to be operated with their valves fully open. The hydrant sampler was
designed to allow the hydrant valve to be fully open while collecting samples in a controlled, safe manner.

When using the hydrant sampler, the user should identify the calculated flush time (CFT) needed at that sample location. Note that:

•	Under-flushing may result in obtaining a water sample from the hydrant service line (i.e., not capturing water quality from the desired location).

•	Excessive over-flushing may result in obtaining a water sample further away from the intended sample location, especially in smaller diameter
distribution mains.

Hydrant Sampling Procedure

1.	Determine the time needed to flush the hydrant lead and riser (CFT) using
the procedure on the next page.

2.	Ask the water system operator for the approximate pressure at the sample
location. If the pressure is > 125 psi, install a pressure-reducing valve (PRV)
adapter. The water system operator should generally operate all aspects of
the hydrant, including:

•	Remove the hydrant outlet cap and connect the sampler to the hydrant,
confirming the gate valve is closed.

•	Slowly open the hydrant until it is fully open.

3.	If the PRV adapter is not being used, record the static pressure on the
pressure gauge.

4.	Open the sampler gate valve and start the timer. Note that the flow control
valve restricts the hydrant flow to a constant rate of 20 gallons per minute
(gprrs).

5.	Allow the sampler to flush for the CFT.

6.	Collect the sample:

•	Close the sampler gate valve and remove the discharge hose,

•	Open the gate valve to achieve a flow rate suitable for sample collection,

•	Close the gate valve between samples and when sampling is complete.

7.	When sampling is complete, close the sampler gate valve and have the
operator:

•	Slowly close the hydrant valve,

•	Open the sampler gate valve slightly to release any remaining pressure For more information, please refer to the Hydrant Sampler Parts List (EPA 815-B-
and confirm the hydrant is fully closed,	18-008) at https://www.epa.gov/sdwa/hydrant-sampler-procedure-and~parts-

•	Remove the sampler from the hydrant.	Iists

Office of Water (MS 140)

EPA 815-B-23-010

December 2023


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Determining the Calculated Flush Time (CFT) for Representative
Distribution System Sampling from Hydrants using the Hydrant Sampler

When utilizing the hydrant sampler, the Calculated Flush Time [CFT] approach should generally be used (particularly if this will be a routine sample
location for the water system), though field experience has shown that flushing the hydrant sampler for 3 minutes will generally be sufficient (e.g., for
pipe diameters of 6 inches and a pipe length of 30 feet or less).

The CFT is determined using the following steps:

Typical Hydrant Installation

Ground Level

£

Auxiliary Valve

Main

1.	Estimate the total length and diameter of the piping (lead line) between the main and the
hydrant (see hydrant installation figure). Utilize an operator's knowledge of system, a
system/site map, and design standards as needed.

Vertical length/diameter:

¦	The diameter of the hydrant riser
diameter is typically 6 inches and assume
that the hydrant riser is 6 feet long based
on design standards, unless indicated
differently.

Horizontal length/diameter:

¦	The diameter of the hydrant lead is
typically 6 inches, unless indicated
differently.

¦	Measure or estimate the length of pipe
between main and hydrant base. If the
location of the main is unknown, measure
the horizontal distance between the
auxiliary valve to the hydrant and add one
foot to account for distance from the
main to the auxiliary valve.

2.	Determine the necessary flush time from the table, accounting for the vertical and horizontal

pipe lengths and diameters, rounding up to the nearest length. Assume 20 gpm flow rate due

to the flow control valve on the hydrant sampler.

Minimum Calculated Flush Times (minutes) at
20 gpm for various line sizes (inner diameter, ID,
provided in inches).

Hydrant
Riser
Distance

Hydrant Lead Distance

Base

Line Length (feet)

4" ID

6" ID

9

00

5

0.5

0.5

1.0

10

0.5

1.0

1.5

15

0.5

1.5

3.0

20

1.0

1.5

3.0

25

1.0

2.0

3.5

30

1.0

2.5

4.0

35

1.5

3.0

5.0

40

1.5

3.0

5.5

45

1.5

3.5

5.5

50

2.0

4.0

6.5

60

2.0

4.5

8.0

70

2.5

5.5

9.5

80

3.0

6.0

10.5

90

3.0

7.0

12.0

100

3.5

7.5

13.5

Office of Water (MS 140)

EPA 815-B-23-010

December 2023


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