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What to look for in a Reverse Osmosis Water Filter 

When shopping for a Reverse Osmosis (RO) or a Reverse Osmosis/Deionization (RO/DI) Water Filter there are many
options, configurations and vendors to choose from. It can be very bewildering. May we suggest you look through the
various options and our view of their relative value. If you have any questions feel free to e-mail or call us. Yes, you can
get cheap water filters especially if you shop around on-line. However, not all water filters are created equal. You really
need to understand what you are getting for your money. Here are some things to look for in a filter unit:

- Number of stages: This is the first question we usually get. As a rule, the more stages the more filtration. What we
describe here applies to filters offered by AquaFX and may not apply to all vendors.

- A Tap Water Purifier uses only deionization and does not have a Reverse Osmosis membrane. This is a good system
for low volume applications, but without a RO membrane the cartridges can get used up quickly depending on the purity
of your source water

- A two stage is a Reverse Osmosis (RO) unit with only a carbon filter. It does not have deionization (DI) nor does it have
a sediment filter. Without a sediment filter you run the risk of prematurely clogging up your carbon filter. When the carbon
filter fails, it can pass chlorine to the membrane and destroy it.

- A three stage has the sediment and carbon filters, but is RO-only, lacking DI.

- A four stage has a sediment filter, a carbon filter, a RO membrane and a DI cartridge to remove all impurities that the
membrane did not remove.

- A five stage filter is similar to the 4-stage unit but has two DI units instead of one. However, not all 5-stage filters are
the same. Some 5-stages have carbon cartridges (Drinking Water Systems) and some have DI cartridges (RO/DI filters
for aquariums and aquaculture).

- A 9-stage has a sediment filter and a carbon filter, three RO membranes, three DI cartridges plus a booster pump (the
ninth stage) to increased the efficiency of the membranes

- For most marine and reef applications, a 4-Stage unit with one DI cartridge is adequate. Some users prefer a 5-Stage
unit with two DI cartridges {product_snapshot:id=39,false,false,false,} so they can maximize their DI usage and have a
backup in case they are not monitoring their cartridge use closely. A RO-only system is fine for many freshwater
aquarium and a drinking water kit can be added.. A complete RO Drinking Water System can be purchased for home

- Membrane quality: There are several membranes out on the market but Dow and Filmtec are the best. Some are just
plain junk. Membranes are rated by their manufactures. There is no standard, so one manufacturer might report their
output at 100 psi, 70 degrees F and use very clean source water, claiming they have a 100 GPD membrane; when
actually at your home you may get 50 gallon per day. Dow on the other hand is VERY conservative ALMOST always
customers report over production of their membranes rating. Click here to view the Technical Data Sheet of the
membranes we use.

- Membrane flush kit: Used to flush out scale and salt deposits on your membrane. Membrane flush kits help to keep
your membrane in top shape.

- Frame construction: Some units use metal frames, some use plastic. Plastic can warp, sag, crack and break and are
not well suited for larger multiple-stage units.

- Cartridge housing quality: Cheap housings can crack and leak. Not a something you want to come home to.

- Cartridge housing material: Clear canisters allow you to monitor the performance of your cartridges. For example you
can see if your sediment filter is getting dirty or when your DI cartridge is almost used up and you need to order a
replacement before it is used up.

- Pressure gauge: Essential to monitor the back pressure from your membrane. A sure way to know if your membrane is
getting clogged.

- Fittings: Brass fittings or any other metal parts are unacceptable, especially for a reef tank! We really like Quick
Connect fittings. If you ever have to change a membrane or move your filter, this will make your life a lot easier.

- TDS meter (handheld or in-line): Use this instrument to monitor the performance of your membrane and DI units. An inline
TDS meter can monitor the membrane effluent and DI effluent by just flicking a switch.