RO Unit Components: Basic Assembly

[RandalB]

Hi All!

Due to an overwhelming demand, myself and the Simply Discus Team present the first in a series of RO unit education threads.

In this thread I will walk you through some of the basic components that I use when assembling an RO unit and what they are used for.

Please hold questions/comments until the end of my posting, as I will be doing my W/C's while I am doing this thread. After that, feel free!

RandalB

[RandalB]

This particular unit was assembled for a fellow Moderator, Ralph. It is a 5 stage RO/DI unit. The abbreviation RO/DI stands for Reverse Osmosis/Deionization. This particular type of water filtration unit is designed to remove ALL dissolved solid/ionic content from the feed water, leaving the product water's Total Dissolved Solids at 0 PPM.

When I refer to 5 stages, in this case they are:

1) A 5 micron Polypropylene Prefilter (Sediment/Debris Removal)

2) A 1 Micron Carbon Block Prefilter (Dechlorination/Bacteria removal)

3) A Dow Filmtec 1800 series Residental Reverse Osmosis element, 75 Gallons Per Day rating

4) A Dowex C100E Mixed bed (cation/anion) deionization resin cartridge

5) A Granulated Activated Carbon Polishing Filter

In this case the 2 prefilters do the job of removing most of the debris and bacterial content of the feed water and perform the critical task of removing water treatment chlorine from the feed water. As you may or may not know, chlorine destroys RO membranes very quickly.

[RandalB]

Here is a photo of the 3 Filter cannisters that will be used in the construction of the unit. The First two from the left will be prefilters and the last one, the DI unit. These canisters are standard 10" which means they are designed for 9.75" filter elements. 9.75" is industry standard.

Note the use of clear canisters, which allows the user to monitor the condition of the prefilters/DI.

[RandalB]

The cannisters are placed in order and the feed ports are lined up so the input and output sides are matched properly. (outputs connected to inputs).

Next, I use teflon tape to wrap the threads of all the fittings that will be used on the unit. I use John Guest Speedfit (tm) fittings on all aspects of the RO unit. This type of fitting allows quick assembly and ease of maintenance. The Tape keeps the fittings from leaking.

[RandalB]

Next,
the fittings are attached to the prefilters cannisters with a wrench. Straight fittings are used for the First feed connection and the last filter connection because they will be fitted with 180 degree rotatable fittings for ease of installation by the user.

[RandalB]

Next,
A white powder coated steel bracket is screwed to the top of the cannisters, providing stability to the cannisters and support for the upper stages. Additionally, two Membrane housing clips are attached.

[RandalB]

Here's a top view of the attachments. Note the angled fitting for the DI unit coming through a gap in the bracket.
The screws being used are stainless or galvanized for protection from rust.

[RandalB]

Next,
The Membrane. The most important and expensive part of the unit, the membrane provides filtering action down to the atomic level.

Standard TFC (Thin Film Composite) Membranes have holes that are between 200 and 400 Atomic mass units (1 Neutron=1 AMU). These tiny holes allow water, H2O to pass while trapping larger molecules on the surface of the membrane where they are washed away by waste water.

I personally recommend DOW Filmtec membranes. As the originator of the technology, Dow provides the most efficient and effective membranes on the market today.

[RandalB]

There are two sets of seals on the membrane that are lubricated with silicone lubricant prior to being installed in the membrane housing or vessel:

A double set of O rings, on the product water end, keep the product and waste water from mixing.

[RandalB]

And a larger Flanged O ring that keeps the element centered in the housing. Note the hole in the plastic stem. Once the membrane is in the housing, these holes are used to remove it for replacement using a piece of string or wire.

[RandalB]

The product end of the membrane (2 O rings) is inserted first in the housing.

[RandalB]

The membrane is then slowly and gently seated in the housing to avoid damage to the O rings.

[RandalB]

The housing is then capped and tightened with a wrench. The cap is on the feed water end of the housing.

[RandalB]

The Membrane housing is attached to the mounting bracet with the previously attached clips.

[RandalB]

One of the cheapest but most important parts of the RO unit is the Flow Restrictor. Without it, the unit doesn't work. The flow restrictor provides the pressure that makes the unit work. Flow restrictors are precision calibrated to allow only a certain amount of water to pass in a set time period. If improper sizes are used, the unit will not have enough pressure to push water through the membrane or will not have enough waste water flow to keep the membrane clean of contaminants.

[RandalB]

On my RO units, the flow restrictor is incorporated as part of a flush valve assembly. Flushing the membrane regularly is critical for proper membrane operation.

On other RO units the flow restrictor is either inline, (looks like a cylinder with fittings on either end)or in the waste water fitting of the membrane housing.

Here's a flow restrictor being installed in the flush assembly. Note the black "Tail" goes in the direction of the water flow.

[RandalB]

Here's a finished Flush assembly. It is a simple bypass valve. Turning the blue handle on the ball valve bypasses the flow restrictor that is in the arched tube. The faster flow of water carries away all contaminants on the surface of the membrane.

Membranes catch magnesium and calcium at their surface. Over time, a build-up similar to hard water crust on an aquarium forms. Once this gets too thick the membrane stops functioning and has to be replaced. Operating the flush valve for several minutes prevents this from happening. This maintenance step should be performed weekly to daily depending on your Feed water conditions.

[RandalB]

High Quality 1/4" tubing is then used to connect all the fittings on the unit in proper sequence.

[RandalB]

Here the Product (Filtered water) end of the membrane housing is connected to what will be the DI stage of the unit. 180 degree rotatable fittings are again used.

[RandalB]

Here you see the tube connecting the DI stage to the final or "polishing" stage. Note the gentle Arc of the tube. This is to avoid crimping of the tube and the stopping of water flow.

[RandalB]

Here you see the flush assembly connected to the waste water port of the membrane housing.

[RandalB]

The prefilter and DI cartriges are then placed in their appropriate cannisters.

They are: (from the left)
1) 5 Micron Poly prefilter (solid white)

2) Carbon block (white grid with blue ends)

3) DI (amber colored with white ends)

[RandalB]

The feed water connector and extra hose are then connected to the unit.

[RandalB]

The waste saddle is then assembled and attached to the flush valve with more extra tubing.

[RandalB]

I then assemble the extra free goodies and the unit is ready to be boxed for shipping.

Included with Ralph's unit, Extra Tubing, A self-piercing valve for connecting to steel or copper water feed pipes, A filter wrench, and his choice of a Primo TDS meter or a Checker pH meter.

Detailed instructions for installation, maintenance and operation are also included.

This completes this thread. I know I used terms that may be unclear. Feel free to post with questions. I will try my best to answer all of them.

Thanks for reading,
RandalB

[Ardan]

Excellent Randal!!!

Really well done! :thumbsup: :thumbsup:

[RandalB]

Come on people!

I can't believe I explained things so well that no one has questions! The only stupid question is the one no one asks!


RandalB

Thanks Ardan!

[Ralph]

Great post Randal! And it's all mine, I can't wait.

I got a couple questions.
Does the pressure of the incoming water make any difference?
How do you know when to change the prefilters (that's probably in the instructions though)?
What do people do with the waste water?

Thanks

[RandalB]

Ralph,

The pressure and temperature of the incoming feedwater determine the output of the unit and the amount of waste water produced per gallon of
filtered water.

The Filmtec membranes that I use provide their rated production (75 Gallons per Day in this case) at the following feedwater conditions: 77 Degrees F, 50 PSI (as opposed to Osmotic membranes which are rated at 60) , pH of 8.00 and 200 PPM TDS. Anything below the rated temp or pressure results in the unit producing less filtered water. Higer temps and pressures increase the output. This is why a booster pump is beneficial to people who have cold or low pressure feed water. Lower pH and TDS increase the output.

The freqency of changing Prefilters depends again on the TDS of the feed water. The easiest way to determine if your prefilters need to be changed is to check the TDS of the product water with the handy TDS meter you get free with my RO unit. . In your case Ralph, as this is a DI unit you will have to watch the amount of water produced. If the quantity drops, it is time to change the prefilters. I recommend changing Prefilters every 6 months in water that is 200 PPM TDS or lower, every 3 months in 201 to 400 PPM TDS feed water and monthly in 401 and higher. The Fifth stage polishing filter should be changed yearly. And yes, it's in the instructions.

I know people that let their waste water run down the drain. I also know people that use the water to do water changes in juvenile discus and African cichlids grow out tanks. The Waste water is clean, filtered, dechlorinated water that is slightly higher in TDS than the feed water right from the tap. There is no problem with using this water for W/C's if you have the space to store it. A couple of trash cans or 55 gallon drums with an overflow to the drain would be perfect.


HTH,
RandalB

PS feel free to call or post if you have additional questions!

[Carol_Roberts]

If you don't have a flush kit is the flow restrictor (with the tail) in the end of the blue tubing that connects directly to the membrane housing?

In other words the good product water tubing attaches to the end of the housing and next to it the blue tubing with the flow restrictor for the waste water attaches to the housing. (The other end of the housing has water entering from the carbon prefilter.)

[RandalB]

Carol,
Good question!

It all depends on who made the unit. Not all companies use the precision type flow restrictors. A lot of name brand units use one that is not calibrated and adusted (The purpose of the "Tail") This type will be a small disc with a hole in the center of it. This type will be in the waste water fitting of the Membrane housing (The tube that goes to the drain is the waste water one). An additional type is a cylinder with a compression fitting on either end. These are attached to the waste line somewhere before the drain.

You are exactly right about the placement of the "Good" or Product port, it is generally located next to the waste port. On the housings I use, they are identified with printing on the housing itself. Cheaper ones don't say. The single port on the end cap is for the feed water.

If you are concerned about flushing, all you have to do is remove the flow restrictor and let the unit run for a minute or two and then replace it. The flush valve just makes the flushing process easier.

HTH,
RandalB

[hunterbeav]

Randal is there a place to get the parts cheap to build your own. I know www.airwaterice.com has them, but was wounding if there was anyplace else cheaper? Maybe in bulk. Thanks Jim & Diane :)

[RandalB]

Jim and Diane,

There is nowhere you can get the parts real cheap online. www.wateranywhere.com has most of the components you'll need, but they are kinda pricey too as a retail supplier. I am sure they can supply at a discount if you are buying in bulk.

RandalB

[Ralph]

Is there a problem with using it only during part of the day, like six hours a day? Is there anything special that I have to do?

[Carol_Roberts]

I'm filling my barrel twice a week. Do I need to run a little water through it everyday?

[RandalB]

Carol,
Are you still keeping the unit in the fridge when not in use? If so then twice a week is fine. I recommend running water through the unit at least every 48 hours to keep bacterial growth down.

The membrane and the carbon filter are the most vulnerable to bacterial penetration. Bacterial Penetration is also a common reason for membrane failure.

I've always wondered why you don't do a drinking water system with your RO unit....

Ralph,
Six hours a day is no problem at all. Nothing special needed.

RandalB

[Carol_Roberts]

No refrigeration - sitting on the bathroom counter. That's why I been trying to run some water through it. . . Would a half hour per day work?

[RandalB]

That should be fine Carol. Bacterial growth will just shorten the life of the membrane. The unit will either stop producing water altogether or produce high TDS water if it bacterially fouls. Regular flushing and running the unit daily will be adequate prevention.

RandalB

[RandalB]

Hey Jim and Diane,
Did www.wateranywhere.com help you out? Just to give you an idea about how much RO units really cost to make, I get the parts at wholesale and I make about $20.00 a unit on them. I use the really high end parts and provide a lot of extras though. If you want bulk parts to make a basic unit, I can order whatever you want and have it shipped direct. It will cost you some fish though.

RandalB

[Ralph]

Is it alright to run input water as a mixture of hot and cold water (luke warm)?

What kind of TDS readings should I be looking for in the outflow water, what levels indicate a problem?

[RandalB]

Ralph,
It is OK to run lukewarm water as long as you keep it below 113F. Over that, the membrane is quickly destroyed.

Do you mean product or Waste water? The product water after the unit is flushed (about 5-8 gallons with a DI) should be 0 TDS. The waste water depends on the feed water. With your unit, anything over 0 means the DI is exhausted.

RandalB

[lwarctic]

RandalB, just a question. I have an R O system and I am starting back up using it. I haven't used it for a while. My TDS is about 15 and my PH is about 7.0. Should I change any of my filters? What readings should they be, before you do change filters? Thanks, Les

[RandalB]

Les,
There are several things I need to know, before I can answer your question. 15 TDS is a little high for an RO unit but I have seen it as high as 40.

What is your feed water like?

How long was the filter stored and under what conditions?

I normally recommend changing the prefilers if the unit was stored for a month or longer at room temperature even if it was stored dry. If the membrane was allowed to dry out it may also be damaged. I don't think it is considering your TDS reading.

The best way to determine if your unit needs new prefilters is if the TDS goes up steadily or abruptly. A steep drop in water produced will also tell the tale.

Let me know your feed water conditions and how the unit was stored and I can give you more info. The brand of unit will also tell me what you can expect. A lot of name brand units use cheap/low grade membranes and they produce higher TDS product water.

HTH,
RandalB

[H Tran]

Randal,

I store my unit (60gpd) in a wooden box out in my backyard. The temp here can get up to 98+ during summer time. I only use it once every three day for about 30 gal of product water. Would this be alright?

Plus, with my rate of usage, how often need I change my prefilter? My RO is made by Kent Marine.

Thanks,

H Tran

PS I love my Hanna combo!! Thanks.

[RandalB]

Hoach,
Your RO unit should be fine outside in those nice Texas summers as long as it's kept shielded from the elements and the feed water temperature doesn't go over 115 F. Which is the damage threashold for the membrane. I personally would run a little more product water through it more frequently to prevent bacteria growth.

I can't recommend how often to change your prefilters without knowing the TDS of your tap water.

HTH,
RandalB

[H Tran]

Randal,

My tap TDS is at 307 ppm.

Thanks,

H Tran

[RandalB]

Hoach,
You should change the prefilters every 3 months.

RandalB

[facet]

Where can I buy this RO Unit ?

[RandalB]

Facet,
Funny you should ask.... ;)


http://forum.simplydiscus.com//index.php?board=13;action=display;threadid=10311

Let me know if you have questions...
RandalB

[ronrca]

What a great job you did Randal! ;) You made it look so easy that Im tempted now to build one! ;D

Good job!

[outlawpc]

Randal:

You mentioned keeping it in the refrigerator to Carol.

1. If a person only ran the unit a couple times a month, will keeping it in the frig be the way to go?

2. If someone wanted to store the unit for a long period of time?

[RandalB]

Jim,

Couldn't wait 'till Sunday 'eh? ;)

In answer to your questions,

The easiest way to go is to run the unit for an hour or so every three days. If you don't use it that much, keep the membrane, membrane housing or the unit itself in the fridge. I don't know what components that manufacturer is using, but most RO membranes are succeptable to bacterial penetration of the membrane which will quickly destroy it.

If you are going to store the unit for a long period of time (after inital wetting) remove the membrane from the housing and place it in a ziploc with dechlorinated or RO water, put it in the fridge and change the water every couple of weeks. I also recommend changing the prefilters before placing the unit back into operation.

RandalB

[nokoto]

Hi all

Great posting, on RO... better than the mag's ;D

OK tip: ensure you do not leave you RO outside where JACK FROST can get it since in will damage the membrane as this is filled with lot's of tiny holes (correct guys+girls) if frozen this expands and mkes the holes bigger thus damaging the membrane.

Reason I mention this because I use mine on a hose pipe, and have to bring mine in when it's winter, I cant fix nor plumb mine in... (NOT MY HOUSE YOU SEE) :(

The other thing I was going to say you can double your out put of RO and reduce waste buy having 2 membrane's inline... ( Just a little tip I was told) ;)

Crack on with the good work...

So much info...

Web worm wayne ....

[RandalB]

WWWayne,

Exactly right on the membranes, don't let them freeze.

Why not get a faucet adapter for your RO unit and run it on your kitchen or Bathroom sink? They are pretty cheap and available.

It's not a good idea to run a second membrane on the waste water line of the first. The decrease in waste flow will quickly damage the membrane on the first one. If you mean to add a second membrane/housing off the same tap feed as the first, that's no problem.

RandalB

[bach]

I did not see any pictures as your explaination. Is something wrong with your system?