THE BASICS of SFR
 Spotting is caused by mineral salts, TDS (total
dissolved solids), which are left behind when
water evaporates.
 Spot Free Rinse water must have less than 40 ppm
of TDS. Our preferred is 25 ppm of TDS or less.
 Average TDS range in the U.S. is 330–410 ppm.
 Softeners do not remove any TDS.
 Spot Free Rinse = More Happy Customers!
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TDS EXAMPLES
FOR
Common TDS Levels
Less than .05 ppm Laboratory grade water
Less than 10 ppm Deionized water, distilled water – (batteries, irons)
Less than 40 ppm Typical spot free water – we prefer less than 25 ppm
Less than 150 ppm High quality bottled drinking water
Less than 225 ppm Acceptable quality tap water
333 – 410 ppm Average TDS in the United States
Greater than 500 ppm Not recommended for human consumption (USEPA)
Greater than 1,000 ppm Not fit for human consumption – potential health hazards
35,000 ppm Sea water
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WHAT YOU SHOULD KNOW
About Your Water Supply
Before Getting a Spot Free Rinse System
 Total Dissolved Solids (TDS)
 Hardness
 Iron
 Is water chlorinated or non-chlorinated?
 pH
 Temperature Variation
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TERMINOLGY
FOR
Reverse Osmosis
FEEDWATER
Water fed into the system that requires improvement in
quality.
PERMEATE
The product of the RO system.
CONCENTRATE
The reject from the RO system.
PERCENT REJECTION
(Feed TDS – Permeate TDS) ÷ Feed TDS
PERCENT RECOVERY
(Gallons/Hour Permeate) ÷ (Gallons/Hour Feedwater)
OSMOTIC PRESSURE
The pressure corresponding to the difference in liquid.
SEMI-PERMEABLE MEMBRANE
A selective membrane that allows some materials to pass
through it and other materials cannot.
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INSTALLATION SCHEMATIC
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REVERSE OSMOSIS TREATMENT
PRETREATMENT

Pretreatment of the feedwater is generally required to eliminate
damaging or fouling the RO membrane.

Softening to remove hardness minerals which can scale membrane
(for over 25% RO recovery).

Carbon adsorption for free chlorine removal to protect TFC
membranes. Chloramines OK. Should be backwashing type to avoid
biofouling and prolong effective life of carbon.

5 micron sediment removal.

Chemical feed of colloidal dispersants if silica, alum, silt, and/or
polyelectrolytes are present in enough concentration.

Municipal water supplies are more than prone to fouling than ever
before due to excessive use of Flocculants and anti-corrosion
chemicals that raise ph. Colloidal fouling can occur very rapidly and
results in loss of production without much decrease in rejection.
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REVERSE OSMOSIS TREATMENT
RECOVERY

Recovery: the efficiency of an RO system in terms of water use.

The percentage of feed water separated out as pure water.

Water chemistry dictates dictates how much you can recover.

With softened water and well designed system, you should be able to
recover 50% and avoid fouling.

At 50%, the RO system operates very cost effectively with regard to
water use, energy, salt, heat, etc.

In terms of recovery, reject to product ratios are:
50% - 1:1
25% - 4:1
33% - 2:1
16.6% - 5:1
29% - 3:1

For 500 GPD systems and larger, anything less than 33% recovery is
very wasteful and costly. With increasing frequency states are
regulating water usage.
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REVERSE OSMOSIS TREATMENT
Facts About Setting the Percent Recovery

The recovery setting should be dictated by the water conditions.
• temperature
• pH
• hardness
• ion composition
• TDS
• silt density index

The key is to set the “percent recovery” so the impurities don’t
permanently deposit on the membrane surface.
GENERAL RULES *
(Temperature not to exceed 77° F.)
Very Hard Water
Up to 20 grains
Percent Recovery should not exceed 25%
(3:1 ratio)
Slight-Moderately Hard Water Supply Percent Recovery should not exceed 33%
Up to 5 grains
(2:1 ratio)
Softened Water (pretreated)
Less than 1 grain
Percent Recovery should not exceed 50%
(1:1 ratio)
* Understand that these are general rules that are not 100% correct in all cases
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REVERSE OSMOSIS TREATMENT
Facts About Setting the Percent Recovery
“GENERAL” RULES
(Temperature not to exceed 77° F.)
Very Hard Water
Up to 20 grains
Percent Recovery should not exceed 25%
(3:1 ratio)
Slight-Moderately Hard Water Supply Percent Recovery should not exceed 33%
Up to 5 grains
(2:1 ratio)
Softened Water (pretreated)
Less than 1 grain

Percent Recovery should not exceed 50%
(1:1 ratio)
Understand that these are general rules that are not 100% correct in all
cases
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OPERATING GUIDELINES
FOR
Reverse Osmosis Systems
 Change prefilter cartridge every 90 days minimum
 Lubricate motors yearly
 Test for free chlorine weekly
 Test for soft water daily – Test Strips, Test Kit
 Monitor weekly (minimum):
• Flow rates
• Operating pressure
• Feedwater temperature
• TDS (total dissolved solids)
 Check clock and settings on GAC filter
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