c/p frpm reefaddicts.com
So what is TDS creep? When water sits in the membrane housing for a duration, TDS rises as it wicks out of the membrane. The initial 60 to 90 seconds when the system turns on will send this burst of TDS into the DI resin, or into the sump if it was plumbed directly (without a DI stage to pass through first). Each time the RO system turns on, this occurs. When one is plumbed directly to the tank, the constant on / off process day-in and day-out reduces the membrane's lifespan and efficiency.
Does TDS even matter if I'm getting 0 out of the DI stage? My reply would be "How would you like to save some money?" Membranes work best when they run for longer periods of time instead of short bursts. Some LFS (local fish stores) opt to never turn off their water purification systems to maintain the lowest TDS possible from the constancy of water passing through the membrane(s) at a consistent PSI, choosing instead to doing massive water changes in the selling systems to use up any excess water that would otherwise overflow their storage tanks. As hobbyists, we tend to save anywhere we can, including water usage. We care about every drop of water, what filters cost, and how we can avoid being wasteful.
been investigating this in some depth since i changed my membrane and noticed the jump in tds when it first starts up after i take water from my system,