Combining RO/DI units?

[giulianom]

So here's the scenario:

I have two RO units, one that's a full 4-stage RO/DI, and one that's only a 3-stage RO unit.

The 4-stage (2 filters, RO, and DI) is a nice sleek black model from SEA...

The 3-stage is a dusty white Coralife model.

Both have 75-GPD membranes.


Sexy SEA:

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Bland Coralife:

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What I want to do is to combine the two into a 6-stage, dual 75-GPD (150GPD water saver) RO/DI system, with the two membranes connected with the dirty water output of the first membrane feeding into the input of the second membrane.


I already have a booster pump, ASOV, pressure gauge, inline TDS, etc..

What I need to know are basically how many filters do I need, what kind, and in what order should the be plumbed together.

Thanks!

 

[seth the wine guy]

I was just considering this G but decided against it for the simple fact that I don't think you will have the proper flow from the waste water line needed. You will either restrict the water from the waste water line causing an improper amount of water pressure on the RO bladder of the first unit or you won't have enough water supplied from the first unit's waste water to pump through your second unit at the proper pressure. Either way, the only way it would work is to have the booster pump on the second unit. Putting too much resistance on the waste flow from the first unit will cause more than one problem.
To make it work I think you would need two adjustable booster pumps. I was about to order a second one to try it because of the massive amount of waste water I produce. I'm still trying to think of the best way to tackle this issue. I think I just need a massive waste water container to then use gravity feed to a booster pump. Let me know how it all works for you. Creating stress on the RO bladders may produce 0 TDS but IME that 0 TDS is deceptive because it comes with .05-.10 PO4.

 

[giulianom]

I'm not worried about the membranes - though I may replace the Coralife one and just keep the housing parts.



BRS sells an upgrade kit that shows you how to do the cascading RO membranes:



http://www.bulkreefsupply.com/brs-150-gpd-water-saver-upgrade-kit.html">http://www.bulkreefsupply.com/brs-150-gpd-water-saver-upgrade-kit.html</a>



They recommend 65psi for it to work, and I have that with the booster pump.





I thought that since I already had most of the parts, maybe I could just turn it into a 6-stage dual membrane.

 

[seth the wine guy]

I don't worry about membranes for live expectancy. It's about PO4. I haven't posted my adventures with RODI's and PO4 much at all, but, if you don't want to pump PO4 into your tank you'll need to be careful. Marc Levenson and I were exchanging notes about this very issue just a couple weeks ago. I think it's a widespread problem that very few people realize they have.

 

[giulianom]

Ok, forget about dual membranes for now - I want 150 GPD, should I just replace the single membrane with a 150 GPD version?



The thought there is also to use the 2 additional canisters for a 6-stage...



But the question I had on those is how many of what type...

 

[buckeye field supply]

Sure. Don't forget to also replace your flow restrictor.

Russ

Edit: I'd think about a default configuration with 4 filter stages:
sediment-&gt;carbon-&gt;RO-&gt;DI

Add additional stages if, and only if you have some specific contaminant you're tring to address (for example: chloramines or heavy sediment loads), or other goal you're trying to accomplish.

Don't fall into the trap of thinking that more filters = better filtration. Remember that each prefilter you add causes a loss of pressure reaching the membrane.

Russ

 

[giulianom]

Speaking about pressure, where in the plumbing chain does a booster pump go?

I have mine in between the water source and the first filter.

I get about 65 PSI to the membrane according to the pressure gauge.

 

[rjrgroup]

Seth The Wine Guy;914868 wrote: I don't worry about membranes for live expectancy. It's about PO4. I haven't posted my adventures with RODI's and PO4 much at all, but, if you don't want to pump PO4 into your tank you'll need to be careful. Marc Levenson and I were exchanging notes about this very issue just a couple weeks ago. I think it's a widespread problem that very few people realize they have.

+one Godzillian times...that's a lot

^^^trademark: RJRGroup

 

[buckeye field supply]

GiulianoM;914979 wrote: Speaking about pressure, where in the plumbing chain does a booster pump go?

I have mine in between the water source and the first filter.

I get about 65 PSI to the membrane according to the pressure gauge.

That's OK, but a better placement is as below:

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Russ