RO Units: Parts and Their Functions
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
Re:RO Units: Parts and Their Functions
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.
Re:RO Units: Parts and Their Functions
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.
Re:RO Units: Parts and Their Functions
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.
Re:RO Units: Parts and Their Functions
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.
Re:RO Units: Parts and Their Functions
When correctly seated it looks like this:
Re:RO Units: Parts and Their Functions
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.
Re:RO Units: Parts and Their Functions
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.
Re:RO Units: Parts and Their Functions
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.
Re:RO Units: Parts and Their Functions
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.
Re:RO Units: Parts and Their Functions
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.
Re:RO Units: Parts and Their Functions
Here's a pic of the Membrane housing attached to the filter bracket with the housing clips.
Re:RO Units: Parts and Their Functions
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
Re:RO Units: Parts and Their Functions
Re:RO Units: Parts and Their Functions
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