View Full Version : MAXR RO membrane

08/03/2015, 04:55 AM
so here is my dilemma, my tap water is horrible, 719 TDS water coming in (city water, not well).

my setup consists of this:

1: 5 micron sediment filter Purtrex
2: 1 micron sediment filter Purtrex
3: 5 micron carbon MATRIKX CTO
4: 75 gpd Dow Filmtec membrane
5-6 DI Resin (non color changeing)

i get right at 60 PSI water prssure, right now I am getting about 29 TDS out of the RO and 0 after DI. as you can figure my DI gets used up fairly quickly.

I am thinking to switch out my membrane for the MAXR membrane in hopes this will lower the TDS of the RO.

is there any suggestions you have on how to make my unit perform better so I don't have to recharge my DI resin so much?



Buckeye Hydro
08/03/2015, 05:07 AM
Hi Sam. Here's some thoughts:
1. Is CO2 a big issue for you? Have to looked into this? If you want more info on this issue let me know.
2. Adding pressure may increase your rejection by 1% or so.
3. Does your feedwater contain chloramine?
4. City water is typically low in sediment. Why are you using two sediment filters?
5. 96% rejection on 700 ppm water isn't bad, but yes, a MAXR would get you the lowest possible TDS RO water.
6. Have you experimented with changing your recovery? Lower recovery may yield purer RO water.


08/03/2015, 05:21 AM
1. I have not looked into CO2, as I thought that was mostly for well water but can order a kit when ordering the membrane, my pH probe is shot and I don't really keep tabs on my pH anymore so never ordered a new one.

2. I have thought about adding a booster pump but wasn't sure about the added expense of one because I had 60psi already.

3. we don't have chloramine in our water according to the city water test.

4. no real reason on useing 2 sediment filters except I had the extra housing so figured I would use it. but it does seem like we have a ton of rust and such in our water. if we leave home for the weekend and come back 2-3 days later our water will come out brownish red for the 1st few seconds.

5. what do you mean by changing my recovery?


08/03/2015, 05:24 AM
here is our city water report also

Buckeye Hydro
08/03/2015, 05:30 AM
RECOVERY is the term used to describe what is talked about in this hobby as the concentrate to permeate ratio (waste water to purified water ratio). RECOVERY expresses, as a percentage, the amount of the feedwater that ends up as purified water. So if you have a 4 to 1 waste to purified water ratio, then you have a 1/5=20% recovery. One of the implications of choking off the waste water as folks in this hobby like to do is that at some point, the purity of the RO water starts to decline (i.e., the rejection declines).

RECOVERY and REJECTION are two concepts/terms that are commonly misunderstood in the reefing world.


Buckeye Hydro
08/03/2015, 05:32 AM
here is our city water report also

No signs of chloramine

08/03/2015, 05:33 AM
ok thank you for explaning that, and no I have not messed around with recovery, have always just used the flow restrictor that came with the unit

Buckeye Hydro
08/03/2015, 05:35 AM
I always recommend that people DON"T use anything beyond 1 sediment filter and 1 carbon block unless they have water quality issues that indicate they're needed. You lose pressure with each prefilter added.

You'll have to be the judge if your two sediment filters make sense in your case.

Buckeye Hydro
08/03/2015, 05:36 AM
Your auto signature.... killin' me with all those parts from other vendors!

Buckeye Hydro
08/03/2015, 05:42 AM
ok thank you for explaining that, and no I have not messed around with recovery, have always just used the flow restrictor that came with the unit

Its worth some experimenting.

I don't think there's anything you could to that would make a dramatic difference in the purity of your RO water - so you're left with some things that each will make a bit of difference - together they'll add up and get you in the best situation possible.

The experimenting on recovery is most easily done if you have an inline TDS meter that measures the TDS of the RO water, and a needle valve (http://www.buckeyehydro.com/precision-needle-valve/) on the waste line to easily adjust the recovery.

To measure the recovery, line up 6 to 8 identical cups in front of your system. With your waste water tube in one hand, and your purified water tube in the other, how many cups do you fill with waste water in the time it takes to fill one with purified? This exercise will get you your waste to purified ratio like I talked about above.

08/03/2015, 05:54 AM
Your auto signature.... killin' me with all those parts from other vendors!

i'm very sorry about that :( I ordered these parts before I even knew about you and even reefcentral for that matter.

I do have a dual inline TDS meter that I have setup to check after RO and after DI.

the last time I did check my waste to purified water I was getting about 4:1. I do have a needle valve that I will hook up and try out different ways though.

I will order the membrane wed. on payday though and mess with the needle valve next weekend when I have some free time.

thankyou agin for your help.

Buckeye Hydro
08/03/2015, 05:59 AM
Good deal! We'll know we've made it to the big time what we make it into your auto signature!

08/07/2015, 06:28 PM
well, got the MAXR membrane, and TDS calibration fluid today and went to town. 1st my TDS meter was off so after re calibrating that and running the new membrane for a while I am very happy with it. haven't messed with the rejection rate though.

Tap - 531ppm
pre DI - 8ppm
post DI - 0ppm

I can already tell it is also produceing water faster than my old membrane also.

and I am gonna add that membrane to my sig line :) as you should be in the big time.

Thanks for your help


Buckeye Hydro
08/07/2015, 06:32 PM
98.5 % rejection on 531 ppm TDS water - that's some good performance!

Buckeye Hydro
09/21/2015, 09:00 AM
Just talked to another customer with some pretty rough well water and a MAXR membrane:
576 PPM feed water
7 ppm MAXR RO water.

98.8% rejection is a beautiful thing!


09/21/2015, 07:47 PM
You got yourself a very good membrane, mine after it runs for a while will drop to 4 or 5ppm pre di stage.