[mike31154]

When I see the term 'back flush', there is potential for confusion, for me anyhow. To me, back flush means sending water back through a system in the opposite direction which isn't how the combination restrictor/flush valves used on most RO systems work. What happens during flushing is that the flow restriction is removed downstream of the RO membrane housing allowing all the source water to bypass over the outside of the membrane. That is, no water is forced thru the membrane walls, but the water is still traveling the same direction. This should help flush any accumulated sludge from the outside of the membrane to the drain. To me, 'back flushing' would mean hooking a water source to the output/drain of the system and forcing it 'backwards'. If one were to do this, all the crud & sludge in the RO housing would be sent back to the carbon & pre filter stages. May be a nit pick, but it helps avoid confusing goofs like me.

I open the flush lever on my flow restrictor for a few minutes before & after every production run. My RO membrane is still producing TDS 1 from a source of 210+ after 3 years 8 months and an estimated 17,000 gallons of throughput. I track throughput on Excel spreadsheet & it is based on RO and DI water produced, plus the estimated waste water using a 1 to 4 product to waste ratio. The original 0.5 micron carbon filter was rated to effectively reduce chlorine taste & odor through 20,000 gallons @ 1 GPM. We don't come close to running 1 GPM through our systems. Although I finally changed that out in July after 3 years of production, it probably could have stayed in longer, although at my estimate of 17,000 gals thru, it was getting close to rated capacity anyhow. My DI media was exhausted so I simply changed the carbon at the same time, more for convenience than anything else. Last time I checked the water for chlorine after the carbon block was some time ago, but it still showed 0. Not all carbon blocks are created equal though, so check the capacity of yours before trying to run it as long as I have & get a swimming pool test kit with chlorine strips included to confirm it's still good or not.

No way I'm going to toss a high quality carbon block on a calendar based schedule like 6 months if I have no idea how much water has gone through it. Sure it's only about $20 for a new one, but it's still a waste if the thing can run for 2 more years at the amount of water I produce. With respect to bacteria, if you run your system at least once a week, I reckon the danger of bacteria multiplying in the standing water in your RO system is relatively low. The water in your pre filter housings will still have chlorine or chloramine in it & the system is totally sealed. Once you turn the system back on & flush it for a few minutes as you ought to, anything bad is going straight to the drain. After applying the restriction to produce water again, it should be all good. I've been using RO water for drinking, making beer, wine etc for years and no issues with bacteria so far. I've never disassembled my unit & disinfected it since starting production over 3 years ago. Change the pre filters when they start turning a tan colour and/or the pressure differential on my gauges increases by several psi.