Reverse Osmosis
System Maintenance
Greetings!
Hope you all had a great holiday weekend.
This
week we will discuss changing the filters and even membranes on
typical residential type reverse osmosis systems. We get a lot
of callers asking when they are supposed to change their filters
to keep their reverse osmosis system working correctly and to
prolong the life of the membrane. Of course the answer depends
on the condition of the water and how much is typically used.
In this article, we'll go over the different types of filters
that most reverse osmosis (RO) systems use and how they work.
This will give you a better understanding of your RO system and
when to change filters.
The
typical residential reverse osmosis system uses a pre-filter,
membrane and post-filter. Probably the most important and most
often changed filter is the pre-filter or sediment filter. The
sediment filter is designed to trap sediment just like the name
says. Sediment can be particulate matter in your water that comes
from your well or water supply lines. Sediment can be rust, sand/dirt,
metal flakes and small chunks of calcium or minerals dislodged
from your water pipes to name a few. These particles must not
be allowed to pass into the RO membrane. They could clog or damage
the membrane material and greatly decrease its useful life-span.
The sediment pre-filter captures these particles and keeps your
membrane safe from potential damage.
The
sediment pre-filter should be changed more often if you do not
have a water softener or whole-house filter up-line of your RO.
A typical family of four with no other water treatment devices
and a well water supply should change their sediment filter every
5 months. More frequently if your water has a reddish tint to
it. In this case, at least a water softener is strongly recommended.
A
family of four with city water and a softner plus carbon filter
should not have to change the pre-filter but once per eight months
or so. There will not be a great deal of particulate matter or
contamination in this type of water system.
A
post filter or carbon filter is usually in place after the membrane.
It is the last filter your water passes through before going to
the holding tank. Many times, a carbon filter is used in conjunction
with a pre-filter. The activated carbon-block filter will filter
out many chemicals and contaminants all on its own. If your reverse
osmosis system has a carbon-block filter before the membrane,
it should be replaced every 8 to 12 months assuming a family of
four and some type of pre-RO water treatment. Because the carbon-block
filter is relatively inexpensive, changing this filter at the
same time as the sediment pre-filter is not a bad idea.
A
post carbon filter is inline after the membrane. Not all systems
have these but most do. It is activated carbon that is used to
"freshen" the water after the membrane. Obviously there
is nothing to be filtered from the water after the membrane, so
this filter is used to add a fresh flavor to the treated water.
This filter should last quite some time and may be replaced once
every couple of years or every time you replace your membrane.
The
membrane is the most expensive part of a reverse osmosis system.
If taken care of with regular pre-filter changes, the membrane
should last years. Keep in mind that different water conditions
dictate differing lifetimes for these membranes. A family of four
with treated city water and regular sediment filter replacement
should expect to get 4 to 5 years out of their RO membrane.
We
use two test ROs at two different locations along with a Sprite
6000 digital TDS (Total Dissolved Solids) meter with controlled
tests at 14 day intervals to arrive at these results. One RO is
located in Lowell Michigan and is a 15 gallon per day CTA REO
Pure on city water (chlorinated) with a Fleck 5600 40,000 grain
softener. The second RO is a KISS International with a 20 gallon
per day TFC membrane located in Alto Michigan. This home has a
Fleck 1500 64,000 grain softener. Both TDS results climbed at
similar rates. When a TDS reading of 7 microsiemens/cm was reached,
the sediment filters were replaced. When it was time to replace
the sediment filters for the second time, the carbon block pre
filter on the KISS unit was replaced.
After
replacement of the sediment filters, the TDS readings for both
ROs were between 0 and 1 microsiemens/cm. Both test homes contain
families of four and also use the RO product for ice making.
A
reverse osmosis system does require a bit of maintainence but
for the cost of sediment
filters compared with bottled water, or tap water filters,
an RO is the most reliable and cost efficient way to go.
