®
WATER QUALITY & CONDITIONING PRODUCTS
Introduction
Watts Reverse Osmosis (R/O) Systems are designed to provide the commercial 
and industrial user with the most trouble free, cost effective and reliable form of 
water treatment available, by providing every option necessary for a successful 
installation.
Principles of Reverse Osmosis
Watts R/O systems employ thin film composite spiral wound membrane 
elements for superior performance. To simply describe the process, pump 
pressure is used to supply source water to reverse osmosis membranes. These 
special membranes allow only high quality water to permeate them. In turn, they 
reject metals, salts, ionic and organic impurities that are processed to waste. 
Suspended solids are removed by pre-filters, which are standard components 
on all Watts RO systems
.
Water temperature
Product water quality and production of any RO system is dependent on 
pressure and temperature. Watts™ RO systems are rated at standard 
conditions of 77˚F (25˚C), 60 psi (4.2 bar) inlet pressure and 1,000 TDS feed 
water quality. Higher temperatures will result in more water passing through the 
membranes and increased water production. As a rule, at given pressures and 
TDS levels, for each one-degree change in water temperature the change in 
water production is approximately 2%.
Water temperature Production Factor*
°F  °C (Using thin film membranes) 
40 4 0.48 
50 10 0.60 
60 16 0.73 
70 21 0.88 
77 25 1.00 
80 27 1.06 
90 32 1.26
*Percent of rated production.
Water pressure
Watts® commercial RO systems require a minimum of 10 psi feed pressure to 
function properly. The maximum pressure is 90 psi, and a pressure regulator 
must be utilized over 90 psi to reduce feed water pressure.
Feed / source water inlet requirements
The source water requirements shown below are essential for proper operation:
Note:
Pretreatment may be required if the above parameters are not met. 
Failure to meet feed water requirements may foul membranes, void the warranty 
and possibly make it necessary to down-rate performance.
All specifications listed are based on an average of 1,000 TDS feed water, 77°F 
(25°C) temperature and 60 psi (4.2 bar) pressure. Typically, higher-pressure 
differentials and higher temperatures increase water production and water 
quality. Maximum pressure and temperature limits must be observed.
Factor Requirement
Hardness <1 grain per gallon 
Free chlorine 0 ppm 
T.D.S. <1,000 ppm 
S.D.I. <5 
pH 3-11 
Iron <0.01 ppm 
Silica <25 ppm 
Manganese <0.05 ppm 
Turbidity <1 NTU 
Temperature 40°F - 95°F (4°C - 32°C) 
Pressure 10 - 90 psi (2.8 - 5.6 bar)
Inlet feed water requirements
Distributed by:
Feed
Water
Scale
Prevention
(Softener)
Chlorine 
Removal 
(Carbon)
Cartridge 
Pre-Filter
High
Pressure
Pump
R/O
Membranes
Waste
Product
Water
General RO Process Diagram
1. System location
The RO system should be located on a level surface in an area sheltered from 
sun, wind and rain. The temperature in this area should be maintained, and 
should not fall below 35°F, nor greater than 95°F. If these limits are exceeded, 
damage to components may result and the warranty may be considered void. It 
is important to allow sufficient space around the unit so maintenance can easily 
be performed.
2. Plumbing
The high-pressure pumps used require a continuous flow of water to the 
system. Minimum feed pressure is 10 psi. Please see table, below for minimum 
flow rates.
3. Feed water
Piping for feed water to the RO system should be either copper or plastic. Iron 
and carbon steel pipe will increase the iron content of the raw feed water and 
adversely affect the RO system's performance. Temperature of the feed water 
must not exceed 95°F.
4. Product water (permeate) line connection
Connect the product water (permeate) line to the manifold on the back side of 
the system. This line should not have valves and should run as directly as 
possible to the storage tank.
5. Concentrate (waste) line connection
Connect the waste line (concentrate) to the manifold on the back side of the 
system. The waste from the system should not have valves and should have an 
air break between it and the building drain system. The tubing or piping used for 
discharge of the concentrate should be run to an open drain in a free and 
unrestricted manner.
6. Electrical
The customer must provide a properly sized electrical service.
Level controls
In most installations it is necessary to use the level switch connector wire to 
install a level control or an electrical switch to turn the RO system on and off 
based on the water level in the storage tank.
Pumps
Never let pumps run dry. Operating pumps without sufficient feed water will 
cause damage. Feed pumps with filtered water only.
Pre-filtration
All Watts® RO systems come with particulate pre-filters to remove suspended 
particles down to five (5) micron in size. Change pre-filter cartridges at least 
every month or when there pressure differential of 10% or more that start-up 
pressure differential with clean cartridges.
Limited warranty
Watts® Commercial Reverse Osmosis systems are warranted to the original 
purchaser to be free of defects in material and workmanship for a period of one 
year from date of shipment. Should defects occur, Watts will repair or replace 
parts, which are defective. Shipping and labor costs are excluded for this limited 
warranty, and these costs are the customer's responsibility. Normal wear, 
accident, abuse, misuse, unauthorized alteration or repairs are also excluded. 
Watts will not be responsible for any incidental or consequential damages, 
losses or expenses arising from the installation or use of a Watts system. For 
warranty issues please call your dealer or Watts Water Quality & Conditioning 
Products at 800-659-8400.