Dual Membranes Booster Pump and Doser

FirstContact · Sep 8, 2018

Feedback: So this year I added a second membrane and booster pump to my RODI. The booster pump from BRS has worked great. The add on membrane kit not so much. Basically, the waste water from the first membrane fouls the second membrane very quickly and then you just wasted $45 on the membrane and throw more money away on DI resin. Okay. Booster pump has worked great though.

Question: I want to set up a doser with the doser above the dosing containers but about 12 inches below the aquarium. So I will be asking the doser to push the liquids up 12 inches or so. Is that a thing? Can I do that?

pecan2phat · Sep 9, 2018

Strange, I've done the 2nd membrane upgrade and my DI resin does not get used up any faster then when it was a single membrane unit. My membranes are going on 3 years.

miPapareef · Sep 9, 2018

FirstContact said:
Question: I want to set up a doser with the doser above the dosing containers but about 12 inches below the aquarium. So I will be asking the doser to push the liquids up 12 inches or so. Is that a thing? Can I do that?

No problem for a dosing pump. As example, a BRS 1.1ml/min pump has a rated head height of 20 feet.

FirstContact · Sep 9, 2018

miPapareef said:
No problem for a dosing pump. As example, a BRS 1.1ml/min pump has a rated head height of 20 feet.

Thanks much. I’m going to try that then.

FirstContact · Sep 16, 2018

Well, it definitely doesn’t work for me and I’m only feeding my first membrane about 125 ppm TDS. No issues with the first membrane at all; so, it can’t be a problem related to the prefilters or water quality. This is the second membrane I have tried as a dual stage with waste water feeding the second membrane from the first. It definitely just doesn’t work for any reasonable amount of time. I always get several years out of my membranes except this dual stage set up where the waste water goes to the intake on the second membrane. Starts out great measuring at 2 or 4 ppm but that doesn’t last and the membrane is quickly fouled. I even tried reseating it just in case. Nope, doesn’t work. Swapping out the RO tubing making the second membrane the first and the first membrane the second doesn’t work either. That just proves the membrane is fouled. So there’s really no way for the first membrane to continue to work great and the second membrane to fail so soon except for the fact that your feeding it highly concentrated waste water from the first membrane. I wish BRS would explain that in their test video. Either way, I’m going to replace the membrane and feed both directly from the prefilters instead of using the waste water line as a feed source. What do you want to bet both membranes now last for years instead of having the second foul in a matter of months?

I might add, that I think BRS is great, very informative, helpful, and that I enjoy their videos and purchase lots and lots of stuff from them. Thank you BRS!

But again, waste water feeding a second membrane just doesn't work for me. You are all welcome to come over to my house and prove me wrong, but I'm not wasting any more money on this set up.