Shut off: All new residential systems are now required to have a full tank shut off. This shuts off the inlet pressure to the system when the storage tank becomes full. Older RO systems without this feature should have a full tank shut off installed so that the system does not continue to pass water to drain even though the storage tank has reached its capacity. This device alone will save thousands of gallons of water a year. They do not however last forever. Shut offs should be checked once a year to see if they are functioning. This can be done by turning off the storage tank valve and making sure that no concentrate water is running to drain. If you see water running to drain after 10 minutes in a steady stream you should then check your check valve to make sure that it is functioning. If your check valve is OK then you should replace your shut off.

Twist off filters or Bayonet filters: These are filters that can be removed more easily than conventional filters. By simply turning the filter with your hand it will release from the system. These replacement filters are always encapsulated which makes for more sanitary servicing and requires no tools to replace the elements in a system.

Air gap faucet: This protects your entire system from potential contamination from a drain backup. The water running to the drain is vented at the faucet that comes with your system. A proper air gap is a minimum of one inch above the top of your sink. With this gap, if your sink backs up and your system is shut off, water will not run back up into the drain line of your system contaminating it.

Rejection of impurities: This is what your membrane is removing from your tap water. A new reverse osmosis system will remove about 95% to 99% of all TDS or total dissolved solids. As your membrane gets older its rejection of impurities will fall. Once it falls below 85 % it is time to replace the membrane.

TDS meters: TDS stands for total dissolved solids. The best way to check if your system is operating at its peak performance is to do a water quality check. Test the tap water and then the purified water. Take note of the readings for example a typical RO system will get tap water containing 500 ppm of TDS down to around between 5 or 9 ppm. Most of these meters give you a reading in parts per million or ppm of total dissolved solids which is basically everything in the water that cannot be boiled out of it. A TDS meter can range in price from $45.00 all the way to $500.00. You should keep your TDS meter in good condition and check it against an absolute solution of 100 parts per million.