RO Units: Parts and Their Functions

[RandalB]

Hi All!

Here we go again. This series is a step by step walkthrough of a 5 stage RO unit. As I go, I'll show a pic of each part and explain what exactly it does. It's not a how to assemble thing but I show some parts disassembled for greater detail.

As before, I am posting this during W/C's and late at night (my only free time LOL!) So bear with me and please no responses until the I announce the end of the series.

This particular unit was constructed for a Simply Member and I hope they don't mind my using it for educational purposes.


RandalB

[RandalB]

The First part is a Slimline (tm) filter housing.

This particular RO unit will use three of them. They are used for holding the prefilter cartriges. This part is of a type commonly used in RO unit Manufacture. They are commonly referred to as "Cans". They are available in 2 sizes, 10" and 20" the size indicates size of prefilter cartridges not the actual size of the whole Prefilter housing. Most RO units will use them in clear (shown) or opaque white.

They are equpped with two threaded holes for input and output of feed water and are available with multiple hole sizes and threads for various applications, including whole house filtration. This particular one is threaded in 1/4" for use in RO units.

[RandalB]

Here's a closeup of the top of the housing. It shows the direction of water travel through the housing. It is important to have the water flowing correctly. Improper flow will reduce efficiency of the prefilters and the unit as a whole.

[RandalB]

Here's a picture of the inside of the cap. Note the small hole (lighter circle) up to the right. That's the inlet. The hole in the center is the outlet. Correct flow enters on the outside of the prefilter and is forced through the prefilter by water pressure and then out through the center of the cap.

[RandalB]

In the clear portion of the housing, there is also a small ring that holds the prefilter in place during assembly. The correct method for installing the prefilter is to place it in the bottom of the housing, setting the prefilter on the ring and seating it firmly.

[RandalB]

When correctly seated it looks like this:

[RandalB]

The lower portion is then screwed back onto the cap and tightened with a filter wrench.

The way the cap and can are designed, the prefilter will line up properly as the can is tightened.

[RandalB]

This is the Filter bracket. It is the backbone of the RO unit as it provides support for all the other components and a mounting base for the unit itself.

Some Manufacturers use a plastic one. This particular one is Powder Coated steel. Steel provides a more durable and stable support.

Note the holes in the top. They are for mounting the Cans and Membrane housing brackets. They also allow hoses to be routed from below.

[RandalB]

Here's a top view. The screws for holding the cans are stainless steel to avoid corrosion.

Notice all the screw holes are not utilized to hold the cans in place. Some will be used for the membrane housing clips which also use stainless screws for mounting.

[RandalB]

This is a membrane housing clip. Two will be used to hold the membrane housing in position on the top of the filter bracket. The two holes are for hose routing. The clip is mounted with a single screw in the center.

[RandalB]

Here's a pic of the membrane housing clips attached to the filter bracket.

The filter bracket is designed to be used in a variety of different configurations so not all the holes will be used in this one.

[RandalB]

Here's a pic of the Membrane housing attached to the filter bracket with the housing clips.

[RandalB]

This is a Reverse Osmosis Membrane. This part does almost all the work of the unit. The prefilters exist to provide filtered water to the membrane.

This particular one is a Dow Brand Filmtec (tm) membrane and is rated for 100 Gallons per day. The rating is based on set feed water conditions of: 77 Degrees F, 50 PSI, pH of 8.0 and 200 PPM Total dissolved solids. If your feed water is lower temperature and pressure or higher pH/TDS you will get less water per day than it is rated for.

Reverse Osmosis membranes are made of a synthetic polymer that has atomic sized holes throughout it's surface. The pressure of the incoming feed water forces the water molecules through the membrane while trapping the various ionic contaminates on the surface where they are flushed away by the reject or "waste" water. This particular method of removal is called "Cross flow filtration"

Reverse osmosis units operate slowly and are not particularly efficient. At rated feed water values, they will reject 4 to 4.5 gallons of water per gallon of filtered water ("Permiate" or "Product" water). Increasing temperature and pressure of the feed water will increase the efficiency of the unit and will decrease the waste or Reject water.

CAUTION: Feed water temperatures above 115 Degrees F will destroy the membrane as will pressures above 125PSI

The membrane is inserted into it's housing with the two "O" rings on the right side first

[RandalB]

Like this:

[RandalB]

It is very important to lubricate the "O" rings on the membrane prior to insertion into the housing. If this is not done, they may twist or be dislodged during installation and the membrane will not work properly. A good quality silicone gasket lubricant is used.

This picture shows the membrane almost all the way inserted. The end cap will then be screwed on to seat the membrane completely.

As I mentioned in a previous thread, the two holes in the tailpiece of the membrane are to assist in removing it for replacement. A piece of wire is threaded through them and used to extract the membrane from the housing

[RandalB]

This is a close up of the membrane housing cap. It only has one connector on it, this is the feed water inlet. Notice the 180 degree rotatable John Guest fitting, this is provided for ease of removal and installation of the cap. Many manufacturers will use cheap compression fittings on the membrane housing, even though it needs to be removed for servicing periodically

[RandalB]

Here is a closeup of the product end of the housing. Note the outlets for Product and Reject water. This particular housing is fitted with John Guest ports. This adds to total unit cost, but is worth it when it comes time to maintain the unit or replace the membrane

[RandalB]

Here, the Membrane housing is attached to the filter bracket with the membrane clips.

[RandalB]

This is a filter clip.

It is used for attaching a final stage or "Polishing" filter to the membrane housing. 2 of them are used.

[RandalB]

Here, the filter clips are attached to the membrane housing

[RandalB]

This is an inline "Polishing" filter (Omnipure (tm) brand). It traps organic chemicals that make it through the membrane. It is fitted with John Guest fittings for ease of removal and replacement and the filter media is Granulated Activated Carbon. The flow direction is on the label.

[RandalB]

Here, the polishing filter is attached to the membrane housing with the filter clips

[RandalB]

High quality Polyethylene tubing is essential to the operation of the unit. This tubing is 1/4" Outside Diameter and .170" Inside diameter and has a working pressure of 230 PSI.

[RandalB]

The hose connects all the components of the RO unit via High Quality John Guest fittings. These fittings use a push in connection and are very simple to use and virtually leak free unlike the compression fittings that are commonly used in commercially produced RO units. John Guest fittings cost a little more but are worth it for their ease of use and reliability.

Here's a link to more information about John Guest fittings:

http://www.johnguest.com/makeconnect.asp

[RandalB]

Here's the connection between the final prefilter and the Mebrane housing. Note the use of 180 Degree rotatable fittings. This keeps the hose from crimping and stopping the waterflow.

[RandalB]

Here are the first two stages of the unit. They are spun polypropylene sediment filters. The one on the left is a 25 micron and the other is a 5 micron. They are designed to catch solid debris before it can foul the membrane.

[RandalB]

Here is the third stage prefilter. It is a solid Carbon block with 1 micron filtration. The purpose of this stage is dechlorination, microbal filtration and trapping of volitile organic chemicals in the feed water.

Some makers will add a second carbon block in an effort to make their units appear better. The second is not needed in most municipal chlorinated water supplies and not at all in well applications where the water is not chlorinated. A second block can be used to help break the chlorine/ammonia bond in chloramine treated systems, allowing the membrane to reject most of the remaining ammonia.

Granulated Activated Carbon should NOT be used prior to the membrane (As a prefilter) as the carbon dust remaining from manufacture may damage the membrane when the unit is first started

[RandalB]

Here is one of two types of Feed water connectors I provide with my RO units, a faucet connector.

This particular one is made of brass for durabliltity and uses a John Guest connector for the feed hose.

For the reef aquarists who are concerned with copper leaching from the brass, the amount is so miniscule that even if the membrane was not being used, there would be no danger to delicate invertibrates.

The connector is 3/4" Garden hose thread (commonly used in utility sinks) and may require an adapter for kitchen or bathroom faucets

[RandalB]

Here it is again, attached to the inlet hose and port of the 1st stage prefilter. A short hose is used for the photo. On the real unit it would be much longer

[RandalB]

Here is the other type I provide, A self piercing valve. It has the only non push in fitting on the unit. This feed valve is only used on copper or steel pipe (steel pipe requires drilling) where there is no faucet or one is not convienient, such as an under counter installation.

Notice the sharp needlelike projection under the valve body. This is what pierces the pipe.

[RandalB]

Here is the other end of the system, the waste saddle. This is used for attaching the waste line to a drain pipe. A small hole is drilled in the pipe and the saddle clamps around it. The saddle is equipped with another John Guest fitting for ease of installation. The saddle should be attached to the vertical tailpiece of the drainpipe NOT the horizontal pipe after the trap.

Note the gasket, this is vital to preventing leaks and has double stick tape on it to hold it in place,

[RandalB]

Attached to the waste line is a flush valve that contains a flow restrictor.

The flow restrictor provides the backpressure needed by the membrane to force water through it.

[RandalB]

Here is the flush valve assembly. The flow restrictor is located in the "T" fitting on the right. The ball valve in the center when opened, bypasses the restrictor and provides the high flow flush to the membrane surface. Any contaminants are carried away by the water flow and go down the drain.

The waste saddle is off screen to the left and the membrane housing is off to the right

[RandalB]

Last but not least,
Here is a pic of the complete unit. The water feed enters from the fitting on the lower left can and the end product exits from the upper right post filter.

In the horrible photoshop job I did, the red arrows are feed water with chlorine, the yellow arrows are pre-filtered dechlorinated water and the green arrows are product water (RO filtered).

Notice the yellow arrow coming from the waste port via the flush assembly. This water is pure, filtered and dechlorinated water that is only slightly higher in TDS than the feed water. Perfect for growing out young discus.

[RandalB]

That is the final post in this particular thread. Please feel free to post comments and questions.


HTH,
RandalB

[Ardan]

8) :thumbsup:

Another excellent learning thread, Randal !!

Thank You!

[shootingstar]

Randalb,

Oh sht, I have connected wrong.

I have connected from the 3rd filter to the clorine remover then the membrance. have I damaged my membrance. No wonder my pair is acting weir lately.

thanks randalb, excellent material.

[sanmerah]

Hi all
I saw some website http://www.purewater4u.com/store/ERP1000.shtml
sale the Aquatec ERP 1000 Permeate Pump for RO system. They said that it will saves 400% of waste water vs. conventional units. Does anyone know about it? Is it true?
Huy

[RandalB]

Huy.
According to Aquatech who makes that pump 400% is a big time exaggeration. It will help in pressure tank situations where there is considerable backpressure against the membrane. It's pretty much useless in open storage tank systems. All the pump does is force the product water into the storage tank instead of having the normal filter action do it. The pump is driven by the waste water flow. I use one on my drinking water system and with the proper shut-off, I pressurize the holding tank to 80PSI.

I can also easily beat that price if you need one...

RandalB

[JROCK]

RANDAL, THE PRICE ON YOUR COMPLETED UNIT?, DOES THIS INCLUDE PUMP FOR MORE PRESSURE LESS WASTE WATER. ::)

[RandalB]

"J"

Give me an E-mail at Rbogath@aol.com and I'll send you a price list. I give a break for combination RO Unit+Booster kits

RandalB

[justathome]

Hi Randal,
Great artical..
Is it possible you could write down a 'shopping list' of all the components required.
Live in the UK and will start hunting down suppliers and waighing up the cost's.. RO's over here are way more expensive than over your side!!

[RandalB]

Kinda Hard to do for someone from overseas as I don't know what's available.

2-3 10" Canisters w/ 1/4" FPT fittings
1 Metal housing bracket
2x 1/4" Male x 1/4" Quick connect fittings
2x 1/4" Nipples
1 Membrane housing w/ 1/4" QC
1 Filmtec or equivalent membrane
Housing brackets and screws
1 Flow restrictor
2 "T" fittings
1 Ball Valve
1/4" Hose

Kinda General I know,
RandalB

[justathome]

i can get them and the same manufacturer..
The 10" canisters over here are £25..(35-40$)..
will hunt around some more..
My water is GH10 KH5.. will I need all 5 stages??

[discuscraze]

Hi Randal,

Do you have a price for a 3 stage with storage tank and drinking water faucet? I am very interested in getting one for dicus and drinking water (kitchen install).

Please contact me at pavilion10@verizon.net

Thanks
DiscusCraze

[RandalB]

Craze,
You got mail....

RandalB

[heckelcrazy]

Randal can you send me a copy of that email also please?

aranaudra@aol.com

cheers mate

[PsychoKnight]

I have both an air gap r.o. faucet and a standard, single-tube r.o. faucet.
I understand the function of air gap piping on conventional sewer drainage runs, but I don't understand the function or benefit of an r.o. drainage air gap which is built-into an r.o. faucet, especially when the drain line will run into a drainage pipe which is already connected to an existing house sewage air gap.

I'd appreciate any explanations in order to decide if it would be worth the extra effort and tubing to connect the air gap version of the r.o. faucet.

Thanks if you could help me understand.

Okay, think I've figured out the answer to my own question, but I'll post it here in case anyone is also installing an r.o. faucet.
The air gap tubing attachments seem to work like the vacuum breaks on lawn sprinkler systems, so that waste water does not backflush and contaminate the sytem. Calif and Wisconsin code require r.o. faucets w/ a provision for air gap. On websites I've seen, it seems some people have eliminated the air gap function after experience valving problems w/ the air gap, causing a back-up in the waste water flow. At least one vendor recommends that the least problematic method of avoiding sewage contamination is to run the waste water to a garden. However, if draining directly into an undersink drainage, w/out a faucet air gap, a check valve was recommended. Until I can run the waste line to my lawn , I've run a check valve to an extension pipe to raise the waste saddle as far above the horizontal undersink pipe as possible in order to reduce sewage backpressure in the r.o. waste line.

[RandalB]

Damm! Missed this one too..

Yep, most RO manufacturers use Check valves (I do..) instead of air gaps..

RandalB

[drayman86]

Can't seem to view the photos in this EXCELLENT post. Can anyone help me w/ photo viewing? :confused: Thanks!

Greg

[Carol_Roberts]

Sorry - many photos were lost when we moved to the new format

[ronrca]

One quick question. Can I put the DI filter before the membrane or is it recommended to place it after? I think its a DI filter as the filter is plastic with one end removable. Inside there is blue and brownish sand like substance therefore Id assume its not granular carbon.

Also, does it matter at what stage I place the carbon block filter, 1st, 2nd or 3th filter stage? Does it matter at what stage I place the micron filters?

Im totally new and unexperienced with these filters and want to do it right.

Thx



Thx

[RandalB]

DI goes after the membrane, carbon block filter goes 2nd and 3rd in a 4 or 5 Stage RO unit.

If it's one of my RO/DI's, the carbon goes in the middle canister, the DI cartridge goes in the third one.

Yes, that's the DI resin...

RandalB

[ronrca]

carbon block filter goes 2nd and 3rd in a 4 or 5 Stage RO unit.
You use more than 1 carbon block? Whats the advantage for using 2 carbon blocks?

[RandalB]

Helps protect the membrane from chlorine, especially if your local water company decides to spike the chlorine during the summer or after main line work...

RandalB

[ronrca]

But why 2 carbon block filters? Just more effective than 1?

I have chloramine in my tap water unfortunately. It that a problem for the membrane?

[ronrca]

Sorry - many photos were lost when we moved to the new format

To see the photos, check out the library article here:
http://www.simplydiscus.com/library/water_chemistry/ro_di_filtration/ro_parts.shtml

[kevinattwyford]

Hi there Randal,

I'm looking at your RO thread in Cornwall UK with great interest - I'm in the process of installing a 6 stage system at this very moment. I don't see the attachment icon. Any advise?

Best Regards - Kevin

[RandalB]

Kevin,
The pics for this thread are in the library at www.simplydiscus.com

RandalB

[Butch]

Hi Everyone, I have a couple of questions, probably missed in the reading.
Randal, could you post the recommended sizes of the flow restrictors for
the different size membranes.
I have a 75gpd membrane and the flow restrictor has 850 sticker on it.
850 what? Is that the right size?
When I was setting up my RO, put new membrane, I discovered that when
the RO water float cuts the RO water to the tub, the waste water does not
stop flowing. Appears to slow down but not stop. I thought it was supposed
to stop completely. The tubing from the membrane with RO water is tee'ed
back to the bottom of the cutoff valve on the inlet to the membrane.
Sure would appreciate the help.

Butch:)

[RandalB]

Butch,
That's a 850ml/Minute flow restrictor, which means it allows that much water to pass at it's rated pressure. That's fine for a 75GPD membrane that's rated at higher pressure.

As far as the other goes, I'd need a picture to get an idea of what's going on.
Also include the brand of RO unit...

RandalB

[Butch]

Here's a pic Randal. See the blue RO line going from the tee to the water
shutoff valve. The blue line going left out of the picture from the tee is going
to the float valve in the holding tank. The yellow line on the top of the
water shutoff valve is coming from the outlet of the carbon filter. I thought
that when the float valve closed off, it built pressure in the blue line and would shut off the flow throught the yellow line to the membrane. If that is the way it's suppose to work...is the shut off valve sticking. Can I work on
something like that.

Butch:)

[RandalB]

Ahhh, A Kent unit. Gotta Love 'em.

It's either the shut-off solenoid or the check valve in the product fitting of the membrane housing. This is where the blue tube is connected to the membrane housing. Remove that fitting and blow into it. You should only be able to move air through it one way. If not, replace the check valve.

The other possibility is that the operating pressure is not high enough to activate the shut-off. What's your tap water pressure?


RandalB

[Butch]

Thanks Randal. I appreicate the info. Everything is working the way
if should be working. With the float cutting the flow, found a small leak
on the fitting at the storage barrel on the RO line. Explains why the pressure
was not cutting off the valve. Fixed leak now shuts completely off.

thanks
Bert;)

[BobB]

Randal, I am interested in a RO/DI unit for both drinking water and aquarium use. How much would it cost. 50GPD.

[RandalB]

Bob,
I'm not selling anything at the moment, I am in the process of moving.

RandalB

[Robert_Leonard]

Randalb am I missing something as am seeing no pics in this. Was it a victim of the forum going down? If it was that to bad was an excellent thread from when I read it before. Was looking through it again as was thinking on hooking mine up.

[RandalB]

It's actually in the library at www.simplydiscus.com with all the pictures Robert..

Feel free to ask questions when you finish perusing..

RandalB

[dorramide7]

Here's a picture of the inside of the cap. Note the small hole (lighter circle) up to the right. That's the inlet. The hole in the center is the outlet. Correct flow enters on the outside of the prefilter and is forced through the prefilter by water pressure and then out through the center of the cap.

In the clear portion of the housing, there is also a small ring that holds the prefilter in place during assembly. The correct method for installing the prefilter is to place it in the bottom of the housing, setting the prefilter on the ring and seating it firmly.
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[MKD]

hello guys,

I have this ro system installed under my kitchen sink and i replace the red/yellow tubes every 6 months and green/blue every year. By any chance, anyone know if i can re-use the media inside those tubes for discus canister filter? does it help anything?????

http://www.pharmaceuticalwaterfilter.com/images/kcro_mt__94781.jpg

[phil47952]

I'm new to this forum and thinking about getting back into Discus after almost 40 years, my question, can RO/DI water be safe for discus?

[roundfishross]

yes when reconstatuted

[Joker43]

Where are the Pictures?.

[sfdiscus]

Hi - I just bought a CoralLife RO unit (that doesn't come with a water storage tank). Can this forum suggest a cost effective way to store water? What storage should I buy and how much to store up to 20G? thx

[LGelb]

Where are the Pictures?.

try here for the pics http://www.simplydiscus.com/library/water_chemistry/ro_di_filtration/ro_parts.shtml