GE Merlin User guide

GE Infrastructure
Water and Process Technologies
Merlin™
Point of Use
Drinking Water System
Application Guide for Water Treatment Professionals

2 TABLE OF CONTENTS
Rev C
TABLE OF CONTENTS
INTRODUCTION 3
MERLIN DESCRIPTION 4
SYSTEM PERFORMANCE 5
THE MERLIN FLOW SYSTEM 16
MERLIN BOOSTER PUMP 17
PREFILTER 18
MEMBRANE LIFE 20
MERLIN PERMEATE STORAGE SYSTEMS 22
SALT DIFFUSION 23
COMMERCIAL AND INDUSTRIAL APPLICATIONS 29
TROUBLESHOOTING 31
FLOW ESTIMATION WORKSHEETS 33

INTRODUCTION 3
Rev C
INTRODUCTION
This application guide presents guidelines and technical information on
the Merlin, a continuous flow reverse osmosis (RO) water filtration system
designed for residential and light commercial applications
Water treatment professionals should use this guide as an education tool
to help determine the best applications for the Merlin RO system.
Information is included on reverse osmosis systems in general. The Merlin
differences are highlighted where appropriate.
This Application Guide is not intended to be used as an installation or
maintenance manual.
An Installation and Mainenance Manual, PN 1262366, is available from
your Merlin supplier.
The information provided here is not intended to be the answer to every
question the water treatment professional will have. If you have
applications that are unusual, we would like to hear from you.

4 MERLIN DESCRIPTION
Rev C
MERLIN DESCRIPTION
The Merlin is a point of use reverse osmosis system that provides
continuous, on-demand water. It features a breakthrough high
flow-rate technology developed by GE Infrastructure Water & Process
Technologies. The Merlin RO system is designed for residential use and
light commercial applications including:
• Restaurants
•CoffeeShops
• Aquariums
• Grocery Misters.
The Merlin system is the most revolutionary innovation in point-of-use RO
technology since the first such units were introduced. Water treatment
professionals can now offer their residential and light commercial
customers an exclusive improvement over other water purification
methods.
Figure 1

SYSTEM PERFORMANCE 5
Rev C
SYSTEM PERFORMANCE
THE MERLIN SWEET SPOT
The Merlin uses a new, patented membrane element technology that
provides flow rates up to five times greater than standard home RO
membranes. The membrane element is designed to work from 40-80 psi
(2.7-5.5 bar) inlet water pressure and 40-100°F (4.4-37.8°C) water
temperature. The Merlin performs better as pressure and temperature
increase. Ideally, pressures will be higher than 50 psi (3.4 bar) and
temperatures will be higher than 50°F (10°C). Figure 2 represents the
application conditions recommended for the Merlin system.
Figure 2
Flow Rates
Factors that directly affect flow performance from the Merlin include:
• Net driving pressure (NDP)
• Inlet water temperature
• Inlet water conductivity (TDS)
• Installation factors
An understanding of these factors and how they affect flow is critical for
maximizing the Merlin’s performance. To estimate Merlin’s performance,
follow these steps:
1. Determine inlet TDS.
2. Determine inlet water temperature.
3. Determine net driving pressure.
4. Consult Table 1 for estimated flow.
40 50 60 70 80 90
100
90
80
70
60
50
40
Pressure at Inlet (psi)
Degrees Fahrenheit
Red
Ye l l o w
Green
Orange
Red - will require an inlet booster
pump. See page 11.
Ye l l o w - may require an inlet booster
pump. See page 11.
Green - Merlin should work well with
these conditions.
Orange - application in high
pressure/high temperature
installations may result in
reduced element life.
37.8
32.2
26.7
21.1
15.6
10
4.4
Degrees Celsius
2.8 3.5 4.1 4.8 5.5 6.2
Pressure at Inlet (bar)

6 SYSTEM PERFORMANCE
Rev C
Understanding Net Driving Pressure
Net driving pressure (NDP) is pressure available to the elements for
production of permeate water. It is equal to the flowing inlet pressure at
the unit minus the pressure drop throughout the system.
Figure 3
Inlet Pressure
The first step in determining net driving pressure is finding the inlet
pressure to the Merlin. This is the flowing pressure within 12 inches of the
Merlin inlet. Often, this pressure is less than indicated by a home’s well
pump pressure gage.
NOTE: Use the flow rate worksheet located at the end of this
document to estimate flow from the Merlin.
NOTE: Net Driving Pressure = Inlet Pressure - System Pressure Drop.
RO Assembl
y
Faucet
Carbon Postfilter
Elevation
above unit
Length of permeate
tubing
Permeate Line
Inlet Pressure-
Measure as
close to unit
as possible
Obstructions - Elbows,
Tees, etc.
40 psi
80 psi
12 inches
Inlet Line

SYSTEM PERFORMANCE 7
Rev C
System Pressure Drop
Estimating system pressure drop is the second step in determining net
driving pressure. Pressure drops are created by:
• Tubing friction losses
• Obstructions
• Elevation differences
•PostFilter
•Faucet
• Osmonic pressure
Pressure Drop Through Tubing
The Merlin system uses polyethylene tubing to carry the permeate water.
All tubing creates a pressure drop when water passes through it. This
pressure drop is created by friction within the flowing fluid and is a
function of the flow rate through the tubing and the tubing length. To
simplify this explanation, changes in water density because of
temperature, which does affect tubing pressure drop, have been ignored.
The farther the permeate travels through the tubing, the greater the
pressure drop.
To estimate pressure drop through tubing follow the steps below:
1. Estimate flow rate into the tubing using Table 1.
Use inlet pressure into the Merlin as the Net Driving Pressure for
the purposes of this estimation. By using inlet pressure as the Net
Driving Pressure in Table 1, flow directly from the Merlin without
any pressure drop is found.
2. Using the estimated flow rate found in step 1 above, find the pressure
drop through the tubing with Figure 4.
Figure 4
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
Inlet Flow Rate
(gp
m
)
Pressure Drop / ft. Tubing (psi)
1/2" Tubing
3/8" Tubing
.027
.024
.020
.017
.013
.010
.006
.003
0
.75 1.13 1.51 1.89 2.29 2.65 3.03 3.41 3.78
Inlet Flow Rate (Lpm)
Pressure Drop / .304 m Tubing (bar)
Estimated Tubing Pressure Drop For Water Between 40 - 100˚F (4.4-37.8˚C)

8 SYSTEM PERFORMANCE
Rev C
Pressure Drop Through Obstructions
Every obstruction or fitting in the line will cause a small amount of
pressure drop. We recommend keeping connections or obstructions in the
permeate line to a minimum. These include items such as tees, valves,
step-down adapters, elbows, compression fittings, etc.
We recommend subtracting 1/2 psi (0.034 bar) of pressure drop per fitting
used.
Figure 5
NOTE: Do not use 1/4-inch OD tubing anwhere in the installation,
including runs to ice makers. Larger tubing diameters produce less
pressure drop and increase system performance.
EXAMPLE:
Q: A Merlin will be installed with inlet conditions that will produce 0.5
gpm, based on Table 1. The installation requires 20 ft of permeate
tubing. Find the tubing pressure drop.
A: Tubing pressure drop for this installation will be 0.11 psi/ft of
3/8-inch tubing or 0.02 psi/ft of 1/2-inch tubing according to
Figure 4. Because 20 ft of tubing will be used, the total tubing
pressure drop is:
For 3/8-inch tubing: 0.11 psi/ft X 20 ft = 2.2 psi tubing pressure
drop
For 1/2-inch tubing: 0.02 psi/10 ft X 20 ft = 0.4 psi tubing
pressure drop
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Tee Elbow
Stepdown
Fitting
Compression
Fitting
Valve

SYSTEM PERFORMANCE 9
Rev C
Pressure Drop Through Elevation
Faucet elevation can play a major factor in Merlin performance. Faucet
elevation produces a backpressure on the Merlin unit from the elevated
column of water. We recommend minimizing elevation differences
between the Merlin unit and water faucet. Estimate pressure drop due to
elevation according to the following equation:
Pressure drop = 0.43 psi/ft X elevation in feet
(Pressure drop = 0.1 bar/m X elevation in meters)
Figure 6
EXAMPLE:
Q: A Merlin will be installed with 1 tee, 2 valves, and 1 elbow.
Find the obstruction pressure drop.
A: The obstruction pressure drop is found as follows:
4 fittings X 1/2 psi (0.034 bar) each = 2 psi (0.137 bar) obstruction
pressure drop
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Floor
Dispensing Faucet
RO Assembly
Elevation

10 SYSTEM PERFORMANCE
Rev C
Pressure Drop Through Post Filter
The Merlin post filter is custom designed to reduce the amount of pressure
drop as much as possible. The Merlin post filter is designed to provide no
more than a 3 psi (0.21 bar) drop when brand new. Using other post filter/
post treatment methods may cause significantly higher drops in pressure.
Figure 7
The Merlin post filter uses Granular Activation Carbon (GAC). Like all other
RO systems, the post filter is critical for providing the best tasting
permeate water.
Pressure Drop Through Faucet
To estimate pressure drop through the Merlin faucet follow the steps
below:
1. Estimate flow rate into the faucet using Table 1.
Use inlet pressure into the Merlin minus the total pressure drop
caused by tubing, elevation, post filter, and obstructions as the Net
Driving Pressure for the purposes of this estimation.
2. Using the estimated flow rate found in step 1 above, find the pressure
drop through the tubing with Figure 8.
EXAMPLE:
Q: A Merlin will be installed with 8 feet (2.4 m) elevation difference
between the Merlin and the faucet. Find the elevation pressure
drop.
A: The elevation pressure drop is found as follows:
8 feet X 0.43 psi/foot = 3.5 psi elevation pressure drop
2.4 m X 0.1 bar/m = .24 bar elevation pressure drop
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EXAMPLE:
Q: A Merlin will be installed with one post filter. Find the post filter
pressure drop.
A: The post filter pressure drop is found as follows:
1 post filter X 3 psi = 3 psi post filter pressure drop
1 post filter X 0.21 bar = 2.1 bar elevation pressure drop
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SYSTEM PERFORMANCE 11
Rev C
Figure 8
Flow Information
Approximate flow rates from the Merlin system are shown for certain net
driving pressure and temperature conditions in Table 1. Data shown is
based on water containing 750 ppm NaCl. Losses because of osmonic
pressure are included in the Table 1 data. No further adjustment needs to
be made to account for osmonic pressure losses when using 750 ppm
NaCl feed water.
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
16
14
12
10
8
6
4
2
0
Inlet Flow Rate
(gp
m
)
Faucet Pressure Drop (psi)
1.10
.97
.83
.69
.55
.41
.27
.14
0
.75 1.13 1.51 1.89 2.29 2.65 3.03 3.41 3.78
Inlet Flow Rate (Lpm)
Faucet Pressure Drop (bar)
Estimated Faucet Pressure Drop For Water Between 40 - 100˚F (4.5 - 38˚C)
EXAMPLE:
Q: A Merlin will be installed with the estimated flow into a faucet at 0.4
gpm (0.27 Lpm). Find the faucet pressure drop.
A: According to Figure 8, the faucet pressure drop will be 3.8 psi (0.26
bar).
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12 SYSTEM PERFORMANCE
Rev C
Use the flow rate worksheet located at the end of this document to
estimate flow from the Merlin.
In The Followiing Example:
A Merlin will be installed under the following conditions:
Table 1 - Merlin System Flow Rates (gpm), Based on 750 ppm NaCl Inlet Watera
Net Driving Pressureb, psi [bar]
Temperature °F [°C] 75
[5.2]
70
[4.8]
65
[4.5]
60
[4.1]
55
[3.8]
50
[3.4]
45
[3.1]
40
[2.8]
35
[2.4]
80 [27] 1.03 0.95 0.88 0.81 0.74 0.67 0.60 0.53 0.46
70 [21] 0.89 0.83 0.77 0.71 0.65 0.58 0.52 0.46 0.40
60 [16] 0.77 0.72 0.66 0.61 0.55 0.50 0.44 0.39 0.33
50 [10] 0.63 0.59 0.54 0.49 0.45 0.40 0.36 0.31 0.26
a. To adjust data to actual conditions, multiply measured TDS by -0.0002 and add 0.15. Add answer to
Table data to achieve actual flow rate. Estimated flow change from 750 ppm NaCl =
-.0002 X measured TDS + 0.15
b. Net Driving Pressure = Flowing Inlet Pressure – System Pressure Drop
NOTE: Pressure drop throughout the system is caused by such things
as frictional tubing losses, vertical tubing runs, post filter, faucet, and
obstructions. See section on system pressure drop for more detailed
information.
NOTE: Actual system performance may vary due to manufacturing
tolerances and installation factors.
Inlet Water TDS 300 ppm
Inlet Water Temperature 50°F (10°C)
Flowing Inlet Pressure 60 psi (4.1bar)
3/8-inch Tubing Length 15 ft (4.6 m)
Obstruction(s) In Permeate Line One 90°elbow
Elevation Difference Between Merlin And
Dispensing Location 6 ft (1.8 m)
Post Filter Used? Yes
Faucet Used? Yes

SYSTEM PERFORMANCE 13
Rev C
HOW TO DETERMINE RATE OF FLOW FROM THE MERLIN SYSTEM - NORTH AMERICAN
Example
Inlet Water TDS (measured) 300 ppm
Inlet Water Temperature 50°F
Inlet Pressure 60 psi
3/8-inch Tubing 15 ft long
Obstructions in Permeate Line One 90° elbow
Elevation Difference Between Merlin and Faucet 6 ft.
Post Filter? Yes
Faucet? Yes
Assigned Values
Pressure Drop per Obstruction 0.5 psi
Pressure Drop per Postfilter 3 psi
Pressure Drop in Elevation 0.43 psi per ft
(feet Faucet is above Merlin)
1. Determine the Inlet TDS = 300 ppm
2. Determine the Inlet Water Temperature = 50 °F
3. Determine the Net Driving Pressure of the Merlin system
Net Driving Pressure = Inlet Pressure - System Pressure Drop (Follow instructions below)
3A. Calculate the Flow Rate Adjustment Factor
This factor will be used with Table 1 to adjust the TDS of Inlet Water from 750 ppm to 300 ppm.
-
0.0002
(
300 ppm
)
+ 0.15 = 0.09 gpm
3B. Calculate the Tubing Pressure Drop
Inlet Pressure = 60 psi
Water Temp = 50°F
Use Table 1 to estimate flow rate, 750 ppm NaCl @ 50°F and 60 psi = 0.49 gpm
Adjust Table data for actual TDS using the Flow Rate Adjustment Factor 0.09 gpm
Tubing Flow Rate = 0.49 gpm
+ 0.09 gpm = 0.58 gpm @ 300 ppm NaCl
Use Figure 4 to determine the pressure drop for 1 ft. tubing = 0.138 psi
Tubing Pressure Drop for 15 ft = 15 x 0.138 psi = 2.07 psi
3C. Calculate the Obstruction Pressure Drop
1 obstruction (the elbow) X (0.5 psi) =
0.5 psi
3D. Calculate Elevation Pressure Drop
6 ft elevation X 0.43 psi/ft =
2.58 psi
3E. Calculate Postfilter Pressure Drop
1 postfilter X 3 psi =
3 psi
3F. Calculate Faucet Pressure Drop
60 psi - 2.07 psi - 0.5 psi - 2.58 psi - 3 psi = 51.85 psi
Use Table 1 to estimate flow rate, 750 ppm NaCl @ 50°F and 51.85 psi = 0.40 gpm
Adjust Table Data for actual TDS using the Flow Rate Adjustment Factor 0.09 gpm
0.36 gpm + 0.09 gpm = 0.45 gpm @ 300 ppm NaCl
e
8 and the Inlet Flow Rate o
f
0.49
gp
m to estimate the Faucet Pressure Dro
p
= 4.5 psi
3G. Calculate the System Pressure Drop
(System Pressure Drop = Tubing PD + Obstruction PD + Elevation PD + Postfilter PD + Faucet PD
2
.
0
7
p
si +
0
.5
p
si +
2
.5
8
p
si +
3
p
si + 4.5
p
si = 12.65 psi
3H. Determine the Net Driving Pressure Drop
(Net Driving Pressure = Merlin Inlet Pressure - System Pressure Drop)
60
p
si -
12
.
6
5
p
si = 47.35 psi
4. Determine the Merlin Flow Rate
Use Table 1 to estimate flow rate, 750 ppm NaCl @ 47.35psi and 50°F = 0.38gpm
Adjust Table Data for actual TDS using the Flow Rate Adjustment Factor 0.09 gpm
0.38 gpm + 0.09 gpm = 0.47 gpm
TOTAL MERLIN FLOW RATE = 0.47 gpm
g
gp p
pp ppp
pp
Actual results may vary. Membrane performance may vary ± 15%.

14 SYSTEM PERFORMANCE
Rev C
HOW TO DETERMINE RATE OF FLOW FROM THE MERLIN SYSTEM - WORLD
Example
Inlet Water TDS (measured) 300 ppm
Inlet Water Temperature 10°C
Inlet Pressure 4.1 bar
3/8-inch Tubing 4.6 m long
Obstructions in Permeate Line One 90° elbow
Elevation Difference Between Merlin and Faucet 1.8 m
Post Filter? Yes
Faucet? Yes
Assigned Values
Pressure Drop per Obstruction 0.03 bar
Pressure Drop per Postfilter 0.21 bar
Pressure Drop in Elevation 0.095 bar per meter
(meters Faucet is above Merlin)
1. Determine the Inlet TDS = 300 ppm
2. Determine the Inlet Water Temperature = 10°C
3. Determine the Net Driving Pressure of the Merlin system
Net Driving Pressure = Inlet Pressure - System Pressure Drop
3A. Calculate the Flow Rate Adjustment Factor
This factor will be used with Table 1 to adjust the TDS of Inlet Water from 750 ppm to 300 ppm.
-
0.0002
(
300 ppm
)
+ 0.15 = 0.34 Lpm
3B. Calculate the Tubing Pressure Drop
Inlet Pressure = 4.1 bar
Water Temp = 10°C
Use Table 1 to estimate flow rate, 750 ppm NaCl @ 10°C and 4.1 bar = 1.85
Lpm
Adjust Table data for actual TDS using the Flow Rate Adjustment Factor 0.34 Lpm
Tubing Flow Rate = 1.85 Lpm
+ 0.34 Lpm = 2.19 Lpm @ 300 ppm NaCl
Use Figure 4 to determine the pressure drop for .304 meter tubing = 0.0095 bar
T
ubing Pressure Drop for 4.6 m = 4.6/0.304 x 0.0095 bar = 0.143 bar
3C. Calculate the Obstruction Pressure Drop
1 obstruction (the elbow) X 0.03 bar =
0.03 bar
3D. Calculate Elevation Pressure Drop
1.83 m elevation X 0.095 bar =
0.18 bar
3E. Calculate Postfilter Pressure Drop
1 postfilter X 0.21 bar =
0.21 bar
3F. Calculate Faucet Pressure Drop
4.1 bar - 0.14 bar - 0.03 bar - 0.18 bar - 0.21 bar = 3.54 bar
Use Table 1 to estimate flow rate, 750 ppm NaCl @ 10°C and 3.54 bar = 1.32 Lpm
Adjust Table Data for actual TDS using the Flow Rate Adjustment Factor 0.34 Lpm
1.32 Lpm + 0.34 Lpm = 1.66 Lpm @ 300 ppm NaCl
Use Figure 8 and the Inlet Flow Rate of 1.66 Lpm to estimate the Faucet Pressure Drop =
0.31 bar
3G. Calculate the System Pressure Drop
(System Pressure Drop = Tubing PD + Obstruction PD + Elevation PD + Postfilter PD + Faucet PD
0.14 bar + 0.03 bar + 0.18 bar + 0.21 bar + 0.31 bar =
0.87bar
3H. Determine the Net Driving Pressure
(Net Driving Pressure = Merlin Inlet Pressure - System Pressure Drop)
4.1 bar - 0.87 bar =
3.23 bar
4. Determine the Merlin Flow Rate
Use Table 1 to estimate flow rate, 750 ppm NaCl @ 3.23 bar and 10°C = 1.44 Lpm
Adjust Table Data for actual TDS using the Flow Rate Adjustment Factor 0.34 Lpm
1.44 Lpm + 0.34 Lpm = 1.78 Lpm
TOTAL MERLIN FLOW RATE = 1.78 Lpm
Actual results may vary. Membrane performance may vary ± 15%.

SYSTEM PERFORMANCE 15
Rev C
Flow Information for Standard Installations
For typical single faucet under-the-sink Merlin installations using only the
components shipped in the box, the following flow rates can be expected.
This information assumes 4 feet of 3/8-inch permeate tubing, 2 feet
elevation difference, use of the faucet as shipped, and no additional
obstructions or pressure drop. Data shown is based on water containing
750 ppm NaCl.
Table 2 - Merlin System Flow Rates, gpm, based on
750 ppm NaCl Inlet WateraTypical Single Faucet Installation
Flowing Inlet Pressure psi [bar]
Temperature
°F [°C]
80
[5.5]
75
[5.2]
70
[4.8]
65
[4.5]
60
[4.1]
55
[3.8]
50
[3.4]
45
[3.1]
40
[2.8]
80 [27] 0.77 0.73 0.68 0.64 0.59 0.55 0.50 0.45 0.40
70 [21] 0.72 0.68 0.63 0.59 0.55 0.50 0.46 0.41 0.36
60 [16] 0.65 0.61 0.57 0.53 0.49 0.45 0.40 0.36 0.31
50 [10] 0.57 0.53 0.49 0.45 0.42 0.38 0.34 0.30 0.26
a. To adjust data to actual conditions, multiply measured TDS by -0.0002 and add 0.15.
Add answer to Table data to achieve actual flow rate. Estimated flow change from 750
ppm NaCl = -.0002 X measured TDS + 0.15
NOTE: Actual system performance may vary because of
manufacturing tolerances and installation factors.

16 THE MERLIN FLOW SYSTEM
Rev C
THE MERLIN FLOW SYSTEM
The Merlin system works like a small commercial RO system. It uses two
membrane elements in series to produce the high flow of permeate. The
concentrate from element one is channeled into the inlet at the second
element, Figure 9.
Figure 9 The Merlin Flow Pattern
SHUT-OFF PRESSURE
The Merlin stops the flow of inlet water when the system is not in use. An
internal shut-off valve will close when pressure in the permeate line
reaches approximately 1/3 of the system inlet pressure. This function
saves water by turning the unit off when permeate water is not being
used. The inlet valve will open, and the Merlin will start making permeate
water when pressure in the permeate line drops to approximately 11% of
the system inlet pressure.
Prefilter
Plugged
Element
Element
Inlet
To Drain
To Faucet

MERLIN BOOSTER PUMP 17
Rev C
MERLIN BOOSTER PUMP
For lower pressure and/or low temperature applications, a pressure
activated booster pump for Merlin is available. Refer to Figure 2 for help
determining when applications may require a booster pump to improve
system performance.
To install, connect the pump to the 1/2-inch inlet tubing, and plug in the
motor. The pump will automatically turn on and off whenever the Merlin is
producing water.
The Merlin booster pump is a variable speed pump designed to produce
water pressure at 62 to 68 psi (4.27 to 4.69 bar) regardless of the inlet
pressure. As with all pumps, make sure the water flow rate is at least 2
gpm (7.6 Lpm).
Pump Specifications
Inlet water pre-pump pressure range - 20 to 60 psi (1.38 to 4.14 bar)
Pump outlet pressure - 60 to 68 psi (4.14 to 4.69 bar)
Necessary water flow for proper pump operation - 2 to 4 gpm (7.6 to 15.1
Lpm)
Pump electrical ratings - 110 to 120 VAC, 60 Hz, 500 watt
Pump duty cycle - intermittent operation - 1 hour
Figure 10
We recommend using only the Merlin provided booster pump. Other
pumps may result in reduced membrane element or system life.
Motor Shell at 1.5 Amps
Thermal
Shut-Off
Temperature
0 10 20 30 40 50 60 70 80 90 100 110 120
200
180
160
140
120
100
80
60
TIME (Minutes)
Pump Housing
Temperature (˚F)
PUMP HEAT RISE
NOTE: The Merlin booster pump is a great way to increase flow for low
pressure applications. The pump will also help increase TDS rejection
and system efficiency.

18 PREFILTER
Rev C
PREFILTER
The Merlin RO membrane elements will not tolerate long-term exposure to
chlorine. All chlorine must be eliminated from the inlet water before
contacting the RO elements.
Standard Carbon Block Prefilter
The standard Merlin prefilter is a carbon block with 5-micron nominal
sediment reduction capability.
Limits For Standard Prefilter
1 ppm chlorine—incoming water
3 NTU of sediment—incoming water
0.3 ppm of iron—incoming water
5 micron - nominal sediment removal capability
Prefilter Life Calculation
The Merlin filter is rated for 5000 gallons (18,900 liters) of inlet water. Use
the following formula to estimate prefilter life:
Example:
Commercial Applications
Commercial applications will use far more water than most residential
applications. In commercial applications, the prefilter may only last a few
days. We recommend not using the standard carbon prefilter on
applications that will use more than 20 gallons (75 liters) of permeate
water per day, Figure 11.
Prefilter life
(days)
5000
4 X Average Daily Permeate Usage (gals)
=
EXAMPLE:
Q: A household uses 4 gallons permeate water per day.
Estimate the prefilter life.
A:
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Prefilter life
(days)
5000
4 X 4 gals
==312.5 days

PREFILTER 19
Rev C
For these higher water use commercial applications, we recommend
using a high capacity carbon cartridge or backwash carbon filter as
pretreatment to the Merlin. Remove the standard Merlin carbon block filter
from the system.
An alternate 10-micron nominal high capacity sediment prefilter is
available for Merlin. This filter can be used for commercial or well water
applications where no chlorine is present in the Merlin inlet water.
This sediment filter is interchangeable with the standard Merlin carbon
prefilter for applications without chlorine.
Figure 11
EXAMPLE:
Q: A light commercial application uses 200 gals (757 liters) permeate
water per day. Estimate the prefilter life.
A:
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Prefilter life
(days)
5000
4 X 200 gals
==6.25 days
Standard Merlin Prefilter
5-micron nominal
3 NTU max turbidity
5000 gal capacity
1 ppm chlorine max at inlet
Alternate Merlin Filter for
Commercial or Well Applications
10-micron nominal
TBD NTU max turbidity
TBD gal capacity
0 ppm chlorine max at inlet
NOTE: Some applications may have water turbidity or iron levels that
negatively affect prefilter life. If a prefilter clogs very quickly, consider
additional pretreatment before the system.

20 MEMBRANE LIFE
Rev C
MEMBRANE LIFE
The Merlin uses a new, patented, RO membrane technology, not an ultra
or nanofiltration membrane.
It is a standard thin film membrane (TFM) style that is not tolerant of
chlorine.
Maximizing Membrane Element Life
Pretreatment is the key to maximizing the Merlin membrane element life,
like all reverse osmosis membranes. To maximize element life, adhere to
the following inlet water conditions.
Chlorine at inlet to element — 0 ppm
Inlet hardness to system — less than 10 grain, 0 grain optimal
Inlet iron to system — less than .1 ppm, 0 ppm optimal
Inlet manganese — less than .05 ppm, 0 ppm optimal
Temperature — 40 to 100°F (4.4 to 37.8°C)
MERLIN RECOVERY VS. EFFICIENCY
One performance measure for a home RO system is the recovery/
efficiency rate. This is a published amount of permeate water produced as
a product of total inlet water used. The higher the recovery of an RO
membrane system, the less waste water is sent to drain.
• Recovery is the measured permeate (product) water volume
produced as a percentage of inlet water consumed. This is
measured directly from the membrane element.
• Efficiency is the measured permeate (product) water volume
produced as a percentage of inlet water consumed.
But,
Efficiency is measured taking into account the complete system. This
measurement includes the storage tank and any other pressure drop
in the system.
Efficiency is the real-world performance that the consumer will
experience. Therefore it is the best measurement of system performance.
The Problem With Systems That Have Storage Tanks
Traditional home RO systems that utilize a tank may be able to boast 18-
25% recovery, however, most operate at much lower efficiency.
As storage tank systems produce permeate water, the tank exerts
pressure drop on the membrane as the tank fills and tank pressure
increases. This pressure drop decreases the membrane elements recovery
significantly as the tank fills. In many cases, the system’s efficiency will
drop as low as 5% when the tank is near full.