2 RO membranes in series - great addition

[dudemeister]

One of the things that has bothered me for some time is the amount of waste water produced when making RO. Its just a waste to let it go down the drain without a good way to repurpose it. Check out the BRS link below. I bought the kit for the second RO and also a 100 gpd membrane to match what I already had running. It used to take 2 days to make 100 gallons of RO. Yesterday I made 50ish in roughly 5 hours. I think the new membrane needs to get conditioned because when I was running one membrane I was getting 0 TDS prior to the DI resin. Now I am getting 1 TDS which is totally fine. For reference the water going in is around 90 TDS.

A worthy addition.

https://www.youtube.com/watch?v=BKu_e7MVLX0

 

[sniper2be]

The water going in May be 90 tds but going in, but going out will be zero in fist stage and 110+ in waste side. The effects of the purification. When adding the second stage ro membrane. You get roughly 99% efficiency which would put out 1.1 tds into your mix giving you .55 by mixing the two just to increase output with less loss of useable water at the expense of a second membrane. I am using the same type of set up and can live with reduced membrane life on the second stage. But it is a sound practice as long as you can live with 1% TDS.

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[dudemeister]

They spell it out in the video pretty well. I think as long as you are good about flushing your membranes it won't be too bad. I'll let you know if I get back to zero TDS but in the mean time I am very happy with the faster fill time with less waste. The DI will take care of that last 1 TDS. I think its worth it.

 

[RTMA]

Two membranes are definately awesome at making water quickly. I have the double membrane set up from BRS and absolutely love it. Makes water in no time flat.

 

[Buckeye Hydro]

If all you're trying to do is cut down on your waste water you can do that by changing a $4 flow restrictor - no need to add a membrane.

 

[dudemeister]

Update- changed the filters today and am getting zero TDS before DI. Nice.



Bucket Hydro- not sure what you mean by that. I am using an Aquatec booster pump to get 90psi to the membranes. There's already a flow restricter on the system per BRS setup. I can't see how further restricting the flow is going to cut down on the waste water however I do see the logic of running waste water into a second membrane.

 

[Buckeye Hydro]

If you stick with just one membrane, but tighten the flow restrictor, you'll get less waste water relative to the amount of RO water produced.

This is essentially what you're doing by adding a second membrane - you are doubling the membrane capacity, but keeping the original 75 gpd flow restrictor. Make sense?

 

[dudemeister]

If you stick with just one membrane, but tighten the flow restrictor, you'll get less waste water relative to the amount of RO water produced.

This is essentially what you're doing by adding a second membrane - you are doubling the membrane capacity, but keeping the original 75 gpd flow restrictor. Make sense?

yes thanks