Calling all RO masters


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I’ve accumulated a bunch of different RODI parts and want to build something that has more production and is still as efficient as what I’m currently running.

I currently have two sediment filters (iirc 5 micron then 1 micron), and 3 carbon filters. Then I have three RO membranes with the waste feeding the next membrane. This gives me about a 1:1 product/waste. Then it goes to a 3 gallon pressurized tank for our drinking water. I had planned to send it through DI before going to the tank but never got around to setting it up and I haven’t seen any adverse effects yet.

I’m happy with my initial 5 stages (sediment x2 and carbon x3), but what I’d like to do is use my other two extra RO membranes and set them up so that I have a combination of them running in series and parallel (a total of 5). I’d split the incoming water line and send it to two pairs of membranes, each waste feeding the input of the other. Then those 4 will feed the final membrane.

I hope this makes sense. Will this actually increase my production while maintaining my efficiency?


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So your biggest challenge with that would be maintaining pressure throughout the system. In order to properly work each membrane needs to have between 60-80 psi, and every membrane will decrease overall pressure in turn. If pressure drops below 60psi you will begin to produce more waste and sacrifice overall production. Without any boost or pressure regulation, 5 membranes would completely defeat the purpose, the last 3 in the series would suffer greatly and end up producing a lot more waste instead. the 4th and 5th especially would end up producing almost nothing but waste, which would render the entire system useless.

To over come this you will need several booster pumps throughout the system, and you will also need some pressure regulators to ensure that the pressure stays between 80 and 60psi. Likely you will need a booster on the supply coming into the system, and then a booster with regulator in between membrane 2 and 4.

Whether to run DI or not is really based on what your supply water has in it. I would honestly have an ICP analysis done on the supply water so you know exactly what is in it. I run multiple DI on my system because downtown has older pipes and the supply runs very high in silicate
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First, do you live in a part of town that has chloramines? If not, then this is easier. If so, then it is important that you know and have a plan.

Generally speaking, production and efficiency do not go hand in hand. 99% membranes with very little waste are available, but very low output. Stacking membranes requires pressure, like Syn has said, and it also shortens their life down stream.

Looks like you know this, but DI on drinking water is usually not good.

This town has a crazy wide range of tap water. I live in Longmont where the tap TDS is like 30 (last I checked) and out of the RO membrane, I am at 1 or 2 and DI lasts a few years. Crazy easy for me. Some have chloramines and have to use massive amounts of helix carbon blocks before they even start the normal process.