Home water filter, reverse osmosis filter, shower filter, whole house water filter
PureWaterExpress.com (we speak English and Japanese)
P.O. Box 47, Harvard, MA 01451, founded in 1984, same location since
888-928-3794 within US,   978-456-8372 from outside US

How much space does the system take up under the sink?

The main unit is about 15 inches wide, 17 inches high and 7 inches deep. The 3.2 gallon capacity pure water reservoir tank is about 12 inches in diameter and stands about 14 inches high.

If you just don't have the space under the sink, are renting for a short time or traveling, our counter-top units are the answer. Model 463 (2.2 gallon reservoir), 445 (1.25 gallon) or 465 (1.0 gallon).            Top  

How often should you replace the filter cartridges?

Years of monitoring our RO's in the field have yielded the following rule of thumb. Critically important to keep the first sediment filter clean (a Conqueror III replacement is $4.30 plus shipping). We provide computer prompted post-sale follow-ups every six months, in which we ask you to examine the sediment cartridge, well before it looks like the one shown. Very easy to open canisters with a plastic wrench we provide. Carbon filters tend to last 12-18 months under normal usage, so it is prudent to change them every year. When you replace the sediment and carbon prefilters as we suggest, the TFC RO membrane will last anywhere between 2-5 years. The exact timing is determined with a TDS monitor (when TDS reaches, say, 60 parts per million), but sensitive pallette can detect the subtle change in taste.

What is the reverse osmosis (RO) process?

Reverse Osmosis is a process in which dirty water is forced through a special cellophane-like RO membrane under elevated pressure. The cold water inlet side must have a static pressure in the range of 40 to 100 psi for our Conqueror series and the tabletop models 460 and 465. The Gladiator series units are used when the inlet water has no, or not enough, pressure. They have a built-in booster pump which pressurizes water to the proper level.

The hole size in an RO membrane is no larger than 0.0001 microns. Water (H2O) happens to be nature's smallest liquid molecule at room temperature and it slowly seeps through the tiny holes in the membrane, while the contaminants consist of much larger molecules and are stopped. Oxygen dissolved in the water also passes through the membrane. That's why RO is used for aquarium where fish can live. The dirty water left behind is drained out at a constant rate determined by the capillary flow controller unit.

In constrast to the RO process, the hole sizes of mechanical and ativated charcoal filters are in the range of 1 to 5 microns in diameter. Aside from the electro-chemical adsorption process in the activated charcoal filter medium, lots of impurities and molecules can and will pass through these holes.

All our RO systems are configured with a combination of sediment, activated carbon and RO filters in series. Each is designed to optimize the system performance and component longevity. They are also equipped with an auomatic shut-off valve. It senses when the storage tank is full, and shuts off the RO process. Therefore the water is not wasted.           Top  

Which impurities does the RO membrane remove?

Does RO remove bacteria and viruses? Can bacteria grow in the RO system?

Yes, RO removes bacteria and viruses
The hole size in an RO membrane is of the order of 0.0001 microns. Bacteria size ranges between 1 and 5 microns and there is no way they can get through. Cryptosporidia and giardia would be like giant gray whales staring at a 1 inch mesh fish net. Protozoas are even larger than bacteria and will not get through.

Viruses are in the range between 0.02 and 0.5 microns. They are still 100 to 2,500 times larger than the holes in the RO membrane and cannot get through.

Yes, bacteria can grow in the RO system
Modern filter materials are designed to discourage bacterial growth, such as synthetic polypropylene and silver activated carbon. However, bacteria sometimes do grow in the RO system, especially in warm climate, and can pose potential health risk. Bacteria in locations preceding RO cannot come through, but those past the RO stage will.

To insure the system is indeed free from bacteria and slime, we recommend that you disinfect an RO unit every year in warm locations and couple of years in milder and northern locations. We have a simple sterilization procedure using Clorox bleach.

For RO systems operating in tropical climate, we recommend an addition of a UV sterilizer stage.           Top  

What are some of the undesirable contaminants in the untreated water?

In the 21 years of replacing filter cartridges, we have seen it all! Whether from a municipal water supply or your own well, the originally pristine white prefilter ends up looking like the one shown. It takes less than a year to completely saturate it with contaminants. It is often greasy, dark and smelly, and you certainly don't want to touch it, least of all drink it. Let's look at the municipal water first. It is generally acknowledged that water treatment plants and the delivery systems are getting antiquated and that the water utility budget is tight.

We do not mean to imply it happens often, but there have been cases of bacteria in tap water adversely affecting people's health, sometimes even fatally (the 1993 outbreak of cryptosporida in Milwaukee). Lead, asbestos and nitrates, all bad for health, have often been detected. Cases of ground water contamination from ethylene glycol (anti-freeze) used in de-icing airplanes or from chemical plants have been reported.

Water from individual wells does not fare much better. We have tested extensively in New England towns where each house has its own well. It is often too acidic, too hard, contains too much iron, manganese or radon. In each case, water to the house is treated by a point of entry system that relies on inexpensive (read impure) chemicals to combat the condition(s). It is best to remove these added chemical impurities before drinking it.

We have detected in well water arsenic, radioactive radon (of up to 100,000 pico Curie/litre), pesticides, lead, copper, ecoli bacteria, nitrates, odor, color, you name it! The safest bet is to take out these impurities from your drinking and cooking water. And a competently designed RO system is most effective against the widest range of these pollutants.           Top  

What about other type of water or filters?

Bottled water is expensive, inconvenient, and you don't quite know its quality. Distillers remove microbes and most minerals and metals, but they may not remove volatile organic chemicals (often toxic) that evaporate at lower than 100°C temperature, because they evaporate first and recondense. Boiling proces drives out oxygen, so fish cannot live in distilled water.

You can purchase numerous inexpensive carbon only filters in various configurations, but they all suffer from too large (relative to RO) filter mesh size of several microns and too short an adsorption cycle (time period in which water is in contact with activated carbon). Things like copper, arsenic, lead, cryptosporidia, giardia and radioactive radon can only be stopped by the RO filter.

Ceramic filters are only mechanical sediment filters with a very uniform hole size of about 0.8 microns in diameter. Since there is no electro-chemical adsorption process involved (as in carbon), chlorine and odor are not removed. The ceramic cartridge is washable.

If you are a person of discernment who wants nothing but the best quality water for you and your family, the answer is the RO purified water.           Top  

---

About us

How to order Other pages: Pure drinking water - Whole house water - Commercial/industrial - Disclaimer

Home page

PureWaterExpress.com, owned by Prosperity Management, Inc.
E-mail (Japanese OK): sales@purewaterexpress.com
Tel: 888-928-3794 (888-water-94) toll-free US,   978-456-8372 outside US
P.O. Box 47,   Harvard, MA 01451 (same location since 1984)


Copyright 1999: Prosperity Management, Inc., Massachusetts corporation