ro/di question

[Water Dog]

While I agree that having a proper waste: product ratio helps extend the life of the membrane, my understanding was always that it is the increased volume and flow rate of the manual flush that makes a difference in "cleaning" the membrane. Although I've never seen any specific recommendation on how often or how long to manually flush the membrane. Ive set my system is set to flush it for 1 minute every half hour and then at the beginning and end of running, but I just arbitrarily set those numbers.

I suspect it's a combination of those 2 things (among other factors) that help increase the life of the membrane.

Yes, there is definitely a large volume of water flowing over the waste side of the membrane when you open the manual flush valve. This is under no pressure, so essentially you’re just dumping water down the drain.

The waste to water ratio however ensures that for every unit of product water made, your scouring the membrane with a given amount of water under operating pressure. This is true flushing of the membrane that remove scale and buildup from the layers of your RO membrane.

Think about the “high efficiency” auto flush units. They use electronics to regularly flush the membrane during operation by using a booster pump to flush the membrane with extremely high pressure jets of water to scour the layers of the membrane under pressure. That is why they can get away with the advertised 2:1 or 1:1 ratios. Those auto flush systems are not superficially running unpressurized water over the waste side of the membrane. There’s a reason all the auto flush units use a booster pump.