Surflo® DC 24V diaphragm booster pump
How Reverse Osmosis Booster Pumps Work
The purpose of the reverse osmosis booster pump is to increase
water pressure going into the RO unit.
Reverse osmosis is a pressure-driven process. Small residential RO
units will theoretically operate on very low pressure--down to 35
psi, according to some membrane makers--but the reality is, you
won't get a lot of water and the product water quality will be
compromised if the unit runs below 45 psi. Low inlet pressure makes
the unit produce more reject water, produce less drinking water,
fill the storage tank more slowly, and produce lower quality water.
RO units run well on typical city water pressure of 60 psi, but
they run even better with a small pump to boost the pressure to 80
psi or higher.
The picture above shows the three essential elements of the RO
booster pump. The white object at left is the transformer. It plugs
into a standard wall outlet and converts to the voltage (most
commonly 24 volts) required by the pump. The large object is the
pump itself. The third device is the pressure switch. It monitors
the water pressure in the RO unit's storage tank and turns the pump
off and on in response to storage tank pressure. The most common
shutoff pressure for undersink home RO units is 40 psi.
The standard pump setup is shown above. The function of the
pressure switch in the tank line is to shut off current to the pump
when the tank pressure reaches a preset level. Default pressure
settings usually provide around 80 psi pressure going into the RO
unit and shut off production when tank pressure reaches 40 psi.
These settings can be adjusted, but it's usually best to leave them
at factory setting.
Do You Need a Booster Pump?
Most city water reverse osmosis users have enough city water
pressure to run their RO unit nicely and they do not need a booster
pump. For example, if your city water pressure is 60 psi or more,
there is little to be gained by adding a booster pump. If your
pressure is 50 psi or less, however, a pressure boost pump will
give your RO unit more zip. You'll have more water, at a higher
pressure, in the storage tank, and the tank will fill faster. The
increased pressure will also improve the economy of the unit (it
will run less reject water to drain) as well as the quality of the
water. RO units thrive on pressure.
Are All Pumps the Same?
Manufacturers often designate pumps by the gallon-per-day output of
the RO unit. With Surflo® 50GPD pump pictured above, the recommendation is for use with
units with membranes that put out up to 50 gallons per day. For
larger membranes, another model, Surflo® 75GPD, is recommended.