RO and RODI - just tested my output

[Greg P]

I have an older Vertex RO unit with 10" canisters and a standard Membrane.
I run a 100GPD CSM membrane and have no info on it. The CSM website is more than I'm willing to look at right now.
I run a 5 micron Carbon cartridge and a 1 micron Pre-Filter.
My source water is generally between 8 and 12 TDS.
My output is always 0 once I flush my unit for 15-20minutes.

I tested my outputs today, @ 60psi

Waste water was 9100mls, with 4400mls RO water.
This tells me I'm getting around 2:1 waste water to filtered water.

Very happy with my unit !!

 

[ecexotics]

very nice ! ever though of getting a booster pump to bump up the psi ?

 

[piranhaman00]

With a source water of 12tds you could use the skip the RO entirely haha, any unit will give amazing results with such clean water! Glad it’s working for you though

 

[Greg P]

very nice ! ever though of getting a booster pump to bump up the psi ?

No need to boost the PSI any higher as it's enough for the Membrane, and I've read higher pressures can cause canisters to fail.

 

[Greg P]

With a source water of 12tds you could use the skip the RO entirely haha, any unit will give amazing results with such clean water! Glad it’s working for you though

Wish I could skip it altogether, but am very pleased with my City water.
Back in about 2000 or so they spent a HUGE amount of money and updated our reservoir with major filtering. Back then, they claimed we had the cleanest water in the world.
I could, and still can, fill a white bucket or the bathtub with tapwater, and it's blue.

Luckily for us here, our water comes from Mountain run-off

 

[Greg P]

The point I'm trying to make is my 2:1 ratio
If you're not getting a decent ratio from your unit, you're wasting water

I've seen units claiming up to 4:1 and that's just ludicrous

 

[Water Dog]

Consider yourself lucky... In your case, with obscenely low TDS source water, that 4:1 ratio is not nearly as important as it is for those with higher TDS source water. The reason for that waste to product water ratio is to preserve RO membrane life. RO membranes need that waste side flush ratio to stay clean while making water. In higher TDS situations, restricting the waste to a lower ratio allows dissolved solids to build up and clog the RO membrane since they’re not being properly flushed during operation.

 

[Ef4life]

Im happy with under 10tds before my di resin. Phoenix has some high tds water. Typically my brs unit is around 4tds output, but my membrane is about due for replacement and it’s been 10-12tds lately. I wish our water was that clean my di resin would almost last forever lol

 

[Greg P]

Consider yourself lucky... In your case, with obscenely low TDS source water, that 4:1 ratio is not nearly as important as it is for those with higher TDS source water. The reason for that waste to product water ratio is to preserve RO membrane life. RO membranes need that waste side flush ratio to stay clean while making water. In higher TDS situations, restricting the waste to a lower ratio allows dissolved solids to build up and clog the RO membrane since they’re not being properly flushed during operation.

So essentially you're saying that the lower the Input or 'tapwater' TDS, the more we can push our Membranes to work harder.
I get 4 to 5 years from a Membrane before I can't achieve 0 TDS. This is with no DI.

I bypass/flush my system for about 20 mins before each time I run it for about 50 gallons.
Flush is between the carbon and membrane.

 

[Water Dog]

I would think so... Based on my understanding of how RO membranes work, I would say the higher the source water TDS, the more important that 4:1 waste to product ratio becomes for properly flushing accumulated dissolved solids off of the RO membrane during operation to preserve membrane life.

Also, I really don’t think you need to flush your membrane prior to operation for 20 minutes upon start up. 30 seconds or so is more than fine for a waste side flush upon start up and shut down IMO. Though not necessarily relevant for you because of the pristine quality of your source water, the more important thing to have on an RODI unit is a DI bypass valve to flush out TDS creep water upon startup to preserve DI resin life.

 

[Greg P]

I would think so... Based on my understanding of how RO membranes work, I would say the higher the source water TDS, the more important that 4:1 waste to product ratio becomes for properly flushing accumulated dissolved solids off of the RO membrane during operation to preserve membrane life.

Also, I really don’t think you need to flush your membrane prior to operation for 20 minutes upon start up. 30 seconds or so is more than fine for a waste side flush upon start up and shut down IMO. Though not necessarily relevant for you because of the pristine quality of your source water, the more important thing to have on an RODI unit is a DI bypass valve to flush out TDS creep water upon startup to preserve DI resin life.

Thanks for the feedback and info

I'll add that I DO need to flush my unit for 10-20 minutes to achieve 0 TDS before producing new RO