Replacement of RO/DI filters

[Starmstr]

I would like a greater understanding of different stage units their filter options. Specificaly I have a 4 stage unit 100gpd and would like to change out the ro for say 30-40 gpd filter. I know there is a restrictor since it also has a DI filter on the last stage but is it the same dia as on a smaller gpd unit? Furthermore there are several carbon, filterfloss ie spun and wound, not to mention the various di's available.
Is there a FAQ around ment for the hobiest? One answer I'm not looking for is the same ol' recharging media post.

Curious and looking for answers.
Starmstr

[Aquatic reef systems]

I copied a post I left on a different board that seems to work for your question.

#1> The first stage on the system is the sediment filter and has little to no affect in removing TDS, this filter is simply intended to protect the carbon filter from particulates in the water that would otherwise clogg the carbon. This filter is the liest expensive of all of the filters and you will notice that as you move up in stages the filters become a little more expensive.

#2> The carbon filter. The carbon filter does not have any notable impact on the removal of TDS either, the function of the carbon filter is to remove VOCs (Volatile organic compounds) from the water. Chlorine, pesticides etc.....
The carbon filter also serves as a particulate filter to catch any particulates that may squeeze throught the sediment filter.
The carbon filter tends to be more strict when it comes to the Micron rating it is assigned. The main purpose of the carbon filter is to remove the chlorine from the water before it gets to the Membrane. A thin film composite membrane is unable to tolerate exposure to chlorine and for this reason it is very important that you change the carbon filter every six months. There are some retailers who sat that the carbons they sell can go longer......
Please ignore them and take my word for it, 6 Months is safe.

#3> The RO membrane. This is where the TDS is virtualy wiped out and this is the most complicated filter in the system.
Also the most expensive.
The RO works by forcing a body of water through a skin like film that does not want to allow water through.
Not like a strainer though, You actually have 2 bodies of water traveling through the same area at the same time one channels the majority of the TDS out the drain and the fluid that is able to permeate the films is distributed to the good water output which is the fitting on the system that feeds the DI Chamber....This filter can last from 2 to 3 years depending on use and TDS saturation in your source water.

#4> The DI. The DI is always going to be the last filter on the system unless you are using some type of specialty media but so as not to complicate things we will just say usually the last one.
The DI filter consists of 2 separately charged resins,
Anion= Negativie
Cation= positive
The combination of these 2 makes the filter a deionization stage.
Cation resin on its own is most commonly found in home water softeners and is very inclined to the removal of calcium, magnesium, iron and like charged minerals.

Also, the flow restrictor is necessary for an RO to function properly regardless of whether or not there is a DI.
You will need to change the flow restrictor when changing the GPD rating of the membrane because each restrictor is designed to allow a certain amount of water through so that there will enough pressure for the water to permeate the membrane.
If you have any more questions please feel free to ask.

Take care
Bryan Crenshaw

[Reefland]

I am just curious, why change the RO membrane to a lesser gpd capacity? Is it something your cosidering or just wondering if it is possible?

Scott Z.

[AquaFx]

Starmstr,

I think you are asking the difference between filters. You pointed out the different ways the sediments are made. You will not find any big difference between them. The only time you will see a big difference in sediment filters is if the are rated "absolute" . The inexpensive ones you buy are rated "Nominal" The former are expensive and used just in labs and the medical industry.

The next thing that is quite interesting is the use of carbon block. Carbon block has been marketed quite well (people expect you to use the block), but GAC has approx. 40% more surface area then the block (due to binding agents that are used to form the block) Contact time is the most important thing in carbon filtration. We have done some work with chlormines and carbon, there are different types of carbon. I can get into it if you like. I like useing the carbon block as a sediment and following with GAC. We do this alot with chlorimines. Also in an effort to increase the benifits of carbon and keep costs down using a full housing of GAC (pick the type) we are experimenting with useing the whole housing instad of just the through away filter.

I hope this helps

[Starmstr]

Scott you ask "I am just curious, why change the RO membrane to a lesser gpd capacity? Is it something your cosidering or just wondering if it is possible?

The reasoning is I'll never use 100gpd typicaly I use 3-6 gallons perday. I have a 40gallon storage tank on the reciving end of my RO/DI unit therefore I only need to run the filter around once a week. Which leaves me with the following questions.

1. Since my storage tank has a ball type of shut off am I using the filters by rejection of water due to the backpreasure?

2. I have reciently purchased a new home and I has a water softener. Will the plumbing of the softener have negative effects on the filters?

[AquaFx]

Starmstr,

As far as the type of float cut off you have on your storage tank goes, you may consider an auto shut off. The Hydraulic version works by stopping the water from passing though the membrane, therefore there is no water passing through your prefilters.
You are not using up your prefilters if you have an auto shut off.
If you are not using an auto shut off you are using up your prefilters and wasting water

Second, Good move! The softener will greatly extend the life of your RO. "every" commercial RO in existence has a softener as pretreatment (or should)