SEPA
United States
Environmental Protection
Agency
Hydrant Sampler Procedure
Office of Water (MS-140)
EPA815-B-16-005
May 2016
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Hydrant Sampler Procedure
Introduction
When collecting water quality samples, taps located at a residence or business are often not
available or accessible in some areas of the system, so hydrants must be used. Dry barrel hydrants
are the most common type of hydrant. They are designed to be operated with their valves fully
open. The hydrant sampler referred to in this procedure was designed to allow the hydrant valve
to be fully open while collecting samples in a controlled, safe manner.
Hydrant Sampler Procedure
1. Determine the time needed to flush the sample line (i.e., "rule of thumb" or calculated
flush time [CFT]) using the procedure on page 6.
2. If the system pressure is > 125 psi at the sample location, install a pressure reducing
valve (PRV) adapter (ask the system operator for the system pressure). See Figure 1
3. Prepare the hydrant for sampler installation (by having the system operator remove the
outlet cap). See Figure 2
4. Close all valves on the sampler (turn the flush valve clockwise and close the sample
valve). See Figure 3 for identification of valves on the hydrant sampler
5. Install the sampler (The system operator should install the sampler). Sampler is affixed
to the hydrant outlet by turning clockwise. See Figure 4
6. Slowly open the hydrant by turning the operating nut counterclockwise until it is fully
open (the system operator should operate the hydrant).
7. Open the flush valve (turn the flush valve counterclockwise) on sampler and start the
timer. The hydrant sampler operates at a constant flow rate of 20 gallons per minute
(GPM). Either (1) allow the sampler to flush for twice the CFT or (2) flush for the time
designated by the "rule of thumb." See Figure 5
8. Open the sample valve to collect samples. Close the sample valve between sample
collection. See Figure 6
If the PRV Adapter is not being used (i.e., the system pressure is < 125 psi), record the
pressure reading from pressure gauge when both the sample and flush valves are closed.
9. Close all valves on the sampler (turn the flush valve clockwise and close the sample
valve) and have the system operator slowly close the hydrant (turn the operating nut
clockwise).
10. Slowly open the flush valve (turn the flush valve counterclockwise) to release any
remaining pressure and confirm that the hydrant is closed.
11. Remove the sampler (have the system operator remove the sampler from the hydrant).
Sampler is removed by turning the sampler counterclockwise.
Page 2
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Hydrant Sampler Procedure
Removing hydrant fitting
Attaching PRV adapter
Figure 1 removing hydrant fitting and attaching PRV adapter
Dry Barrel Hydrant ^ Operating Nut
Outlet Cap
Figure 2 Dry Barrel Hydrant
Page3
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Hydrant Sampler Procedure
Flush Valve
Thermometer
Pressure
Gauge
Discharg
Hose
Sample Tap
Sample Valve
Hydrant
Fitting
Hydrant Sampler
Parts Identification
Figure 3 Hydrant Sampler parts identification without pressure reducing valve
Install hydrant sampler on outlet
Turn clockwise to secure sampler to hydrant
Figure 4 Install hydrant sampler to hydrant
Page 4
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Hydrant Sampler Procedure
Open flush valve, start timer, and flush for determined
calculated time
Figure 5 Flushing
Figure 6 Sample Collection
PageS
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Hydrant Sampler Procedure
Determining the Hydrant Flush Time
(Assumes flow rate of 20 GPM, regulated by hydrant sampler)
The purpose of hydrant flushing: Flushing improves the likelihood that the sample will be
taken from the proximity of the sample location. Under flushing (not flushing for a long
enough time period) may result in sampling from the service line to the hydrant. Over flushing
(flushing for too long a time period) may sample water pulled from another part of the
distribution system.
Approaches:
1. Rule of Thumb - 3 minute total flush time before sampling. Easy to use and acceptable for
one-time sampling.
(Assumes the pipe diameter is 6 inches or less, and the length of the hydrant lead pipe is
less than 20 feet)
2. Calculated Flush Time (CFT) - Flush for two times the CFT before sampling. CFT should be
determined if time permits.
The CFT is determined using the following steps:
a. Estimate the total length and diameter of hydrant piping (see figure, below); utilize the operator's
knowledge of the system, a system site map, and/or design standards, as needed.
Vertical length/diameter:
• Assume the hydrant diameter is 6 inches (unless indicated differently)
• Assume hydrant length is 6 feet (based on design standards)
Horizontal length/diameter:
• Assume hydrant lead diameter is 6 inches
• Measure/estimate the length of hydrant lead pipe between the main and hydrant
base; if the location of the main is not known, 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
b. Determine the necessary flush time (from the table below) based on vertical and
horizontal pipe lengths and diameters; assume 20 GPM flow rate due to the flow control
valve on hydrant sampler.
Page6
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Hydrant Sampler Procedure
Hydrant Installation
Ground Level
Auxiliary Valve
Main
Hydrant
1-
Base
Hydrant Lead
Number of Minutes needed to Flush Hydrant at 20 GPM
Length of
Hydrant Lead
Pipe
1 foot
5 feet
1 0 feet
15 feet
20 feet
25 feet
30 feet
35 feet
40 feet
45 feet
50 feet
55 feet
60 feet
65 feet
70 feet
75 feet
80 feet
85 feet
90 feet
95 feet
100 feet
2 inch
Diameter
0.0
0.0
0.1
0.1
0.2
0.2
0.2
0.3
0.3
0.4
0.4
0.4
0.5
0.5
0.6
0.6
0.7
0.7
0.7
0.8
0.8
4 inch
Diameter
0.0
0.2
0.3
0.5
0.7
0.8
1.0
1.1
1.3
1.5
1.6
1.8
2.0
2.1
2.3
2.4
2.6
2.8
2.9
3.1
3.3
6 inch
Diameter
0.1
0.4
0.7
1.1
1.5
1.8
2.2
2.6
2.9
3.3
3.7
4.0
4.4
4.8
5.1
5.5
5.9
6.2
6.6
7.0
7.3
8 inch
Diameter
0.1
0.7
1.3
2.0
2.6
3.3
3.9
4.6
5.2
5.9
6.5
7.2
7.8
8.5
9.1
9.8
10.4
11.1
11.8
12.4
13.1
12 inch
Diameter
0.3
1.5
2.9
4.4
5.9
7.3
8.8
10.3
11.8
13.2
14.7
16.2
17.6
19.1
20.6
22.0
23.5
25.0
26.4
27.9
29.4
16 inch
Diameter
0.5
2.6
5.2
7.8
10.4
13.1
15.7
18.3
20.9
23.5
26.1
28.7
31.3
33.9
36.6
39.2
41.8
44.4
47.0
49.6
52.2
Depending on the type of pipe material and degree of corrosion inside the pipe, the inner
diameter will vary. These diameters are meant to be approximations.
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