How much better is RO water over regular tap water?
A decent RO
membrane will remove perhaps 95-97% of the total dissolved solids (TDS
) from tap water. An excellent RO
membrane will remove 98-99%+.
How can you tell if the filters need replaced?My guess is that they havent been replaced in a couple of years but it also has not been used in a long time.
You'll require a TDS
meter to determine that as Dmann has stated, and perhaps know the starting total dissolved solids (TDS
) rate of the membrane.
meter will let you know the TDS
of the tap water and RO
water with those you can determine the TDS
rejection rate. Knowing the starting TDS
rejection rate will give you an idea of how far this rate has decreased over time.
Without knowing the starting rejection rate and if the water is being used for a non-reef system you could set your own TDS
maximum limits. For example changing the membrane out when RO TDS
increases to 20ppm or if the rejection rate drops to 90% or less. I'm assuming the system is not a RO
unit (higher RO
will accelerate DI