Introduction: Heavy Duty Under-Sink Water Filter


This instructable is different than most in that rather than lots of details on assembly, it is mostly the presentation of a water filter project, along with a detailed parts list, including sources. 
The city water in my town simply does not taste good… including when used for ice cubes.
I ran the whole gamut of lugging in bottled water to using a variety of the pitcher-based water filters.  Buying bottled water is not only a pain, but it was frustrating that I was paying twice for my water.  Once by paying the town, and second, by buying bottled water.
As far as those pitcher-based water filters, I don’t care which brand you use, they all share the same short comings.  They are slow.  If you want a drink of water next week, AND want some ice cubes, you better start filtering now.  The water slowly dribbles through expensive filters which over time get slower and slower.
I didn’t want or need a whole house system, so the best solution seemed to be some type of under-sink filtering solution.  As I looked into the various choices, I found that unless you bought a very expensive system, you end up with cheap parts that could cause you problems.  One example is the flexible hosing used for interconnection.  Many systems rely on a push-in pressure type of connection, or connectors with barbs to hold the plastic-like tubing in place.  I read of many horror stories where the tubes popped off, leaving the users with a flood in their kitchen.
Another problem with pre-packaged systems is that once you install it, you are locked into their proprietary replacement cartridges.  You may have a hard time finding them, plus they usually need frequent replacing, are expensive, and provide a slow flow rate.

That is why I decided to put together the system I describe here.  Some of the benefits are:

Use of a standard size, heavy duty 10 inch filter housing.
This allows for a wide choice of replacement filters, which can provide hundreds or thousands of gallons of filtered water typically at a flow rate of about 1 gallon per minute.

Screw on interconnecting hoses with stainless steel outer braiding.
Brass adapters and fittings.

A turn off valve allowing for cartridge replacement and total isolation of the filter system, while still allowing water flow to the kitchen sink, as well as the ability to adjust the filter’s flow rate.

A heavier duty filter faucet rather than the typical plastic ones, including a turn handle vs a spring loaded one, to allow for easier filling of large containers.
The trick was in finding all the right parts, as no such kit seemed to be available… hence the parts list (including sources) is the main benefit of this instructable.

Step 1: Block Diagram

Block Diagram

See the parts list that follows for details on the numbered items in the block diagram.

Step 2: Tools Required

Tools Required

Basin Wrench  (makes it so much easier for tightening nuts on the bottom of a faucet)
Adjustable Wrench
Phillips Screwdriver
Teflon Pipe Tape
Silicone Grease

Step 3: Parts List

Parts List     (Total parts cost around  $120)

1 – Water Filter Housing – holds industry standard 10” filter cartridges
Online from:   609-689-3415   #4448K38  $29.68
Manufacturer =  Slim Line #10 Opaque
Polypropylene – blue bottom, black top
1/4" NPT inlet and outlet  /  overall height = 12 1/8” x 4 5/8”
(I chose the blue opaque to keep out any light to prevent algae growth)
Water enters outside of filter, exits from center of filter.
Has pressure release button on inlet side – to aid in unscrewing bottom.
Replaceable “O” ring = Pentek #151117 (made by Buna-N) 3 3/8” ID   1/8” thick
= Industry Standard Trade Size:
Housing comes with:
Wrench (see picture)
1 filter cartridge: C MAX Model MAXETW-975 (see picture)
5 micron filter with carbon – removes sediment, bad taste, odor
Replacement  $13. at:

2 – Mounting Bracket  for filter housing  (comes with screws)
Online from:   609-689-3415   #4422K96  $2.12
MIL-Spec Buna-N O-Ring A75 Durometer, AS568A Dash Number 237  #4198T274   $9.32 for package of 10

3 – Brass Adapter: 1/4” pipe thread to 3/8” compression
Home Depot #LF A24   $5.23  (nut and adapter on 3/8” end not used)

4 – Brass Adapter: 1/4” pipe thread to 1/4” compression
Home Depot #LF A23   $3.32  (nut and adapter on 1/4” end not used)

5 – 48” Flexible Hose – with Stainelss Steel Braid:  3/8” compression each end
ACE Hardware #4061123   $13.99   (2 elbow adapters not used)
Bar Code:  0 82901 02743 0

6 – Brass “T” Fitting: all = 3/8” compression; inlet = captured nut
Home Depot #CT2-666X P  $6.28

7 – Quarter Turn Straight Valve: 3/8” compression; inlet = captured nut
Lowes  Item #272589   Model #K2071PCLF  $7.78    (outlet nut and ferrule not used)

8 – 60” Flexible Hose – with Stainelss Steel Braid:  1/4” compression each end
Online:   $12.63  
  Plumbing Supply Group, 994 E. 20th St, Chico, CA  95928-6712
Tag = C000600
Bar Code:  0 54361 05605 3
Lil Q-Wick-e,
   Hard to find, but need, since most filter faucets = 1/4”

9 – Kingston Brass - Water Filter Faucet  KS819DL - Polished Chrome finish = 3023661S (>   $38.93 
800-462-8166     888-500-9541
1/4" compression input   -  base = 1 3/4"

Step 4: Installation


I started by installing the filtered water faucet.  I already had a hole in my sink which had a filler plug.  The hole had been intended for a separate spray nozzle, but my current faucet had a spray nozzle built into it, hence the plugged hole.
The filtered water faucet fit fine in the standard hole, and had an O ring on its bottom to make a water tight seal.  From under the sink, you would see the 1/4" water feed tube coming out of the bottom of the faucet.  You would slip on the large plastic washer, metal washer, and nut to secure the faucet.  This is where a basin wrench really comes in handy.
While under the sink, I also attached the 1/4" to 1/4" flexible hose to the bottom of the faucet.  Don’t use any teflon tape or pipe dope.  Hand tighten, then go another half turn with an adjustable wrench or basin wrench.

Then I installed the  brass adapters in the input and output of the filter housing.  At the NPT end of brass adapter (going to plastic filter housing), wrap teflon pipe tape around 6 times (in direction of turning, so won’t unwind), but skip first line of threads, to be sure they grab and don’t cross thread.  Tighten by hand, then use a wrench to go in about 1/2 way, (only more if leaks later). 
I then attached the 1/4" flexible hose going to the filter faucet to the output side of the filter housing, and the 3/8” flexible hose to the input side of the filter housing.  This is easier to do before mounting the housing. 
You can then mount the filter housing on the side cabinet wall using the “L” bracket and screws. 
Next, open up the filter housing to install the filter cartridge.  It may not need it until you do a filter cartridge change at some later time, but remove the “O” Ring to see that it has a bit of lubricant on it.   If not, put alight coat of silicone grease on the “O” ring for better seal.  Do not use petroleum jelly (Vasoline) as it could deteriorate the rubber.

Then remove its plastic wrapping and install the filter cartridge.  The cartridge sits between a raised ridge in the bottom of the housing and a section of output tubing in the cover.  Slide the bottom of the housing onto the cover and screw into place.  The housing will not screw closed if the filter does not sit properly I the housing.  You can then use the special wrench that came with the housing to tighten further.

Before proceeding further, you must shut off the cold water supply to the existing faucet.Then I unscrewed the existing 3/8” flexible hose from the existing valve fixture. 

After wiping up any water that was in the hose, you can install the brass “T” and the 1/4 turn valve (have the valve I in the off position).  Then connect the 3/8” flexible hose from the filter housing’s input, to the 1/4 turn valve’s output.  As mentioned before: Do not use pipe tape or pipe dope on compression fittings.  Hand tighten them, then another1/2 turn with a wrench.  
At this point you can turn on the main cold water feed and check for leaks. 

I then wanted to adjust the amount of water flowing to the filter to prevent it from splashing out of the filter faucet, and to have about a 1 gallon per minute flow.  I did this by opening up the filter faucet all the way, then  slowly opening the 1/4 turn valve while monitoring the amount of water flowing out of the faucet.  You will hear the water fill the filter housing, then flow out the faucet.  You may want to use an empty 1 gallon jug to adjust for the flow time.

When the adjustment is done, you should allow at least 2 gallons of water to flow for purging, before using the water. 

Note: This is not a reverse-osmosis system so it does not depend on high water pressure to function properly.  Conversely, I adjusted for the 1 gallon per minute flow rate since that is the value you see on most of the filter cartridges.  From some experimenting, I did find that leaving the pressure going into the cartridge too high, that I did get a bad taste leaching through.

Step 5: Final Notes, and Filter Cartridge Info

Final Notes, and Filter Cartridge info

Even though this filter cartridge is rated for 3,000 gallons, I would change it sooner.  Since I would only use my filtered water for drinking, ice, and cooking, I estimate it would last for several years.  But to avoid bacterial build up, it’s a good idea to change the filter once or twice per year even if you are under the gallon amount.  I intend to put a piece of white tape with the install date on the filter housing, and change the cartridge every 6 months.
When it comes time to change the cartridge, turn off the 1/4 turn valve, open the filter faucet.  At that point you should be able to loosen the housing using the special wrench.  Then you can finish unscrewing by hand.  Have a bucket and some towels on hand since the housing will be filled with water.  Remove the old cartridge, rinse the housing and put in a new cartridge.  Be sure to mark the change date on the housing.

(With the faucet open you probably won’t need to use the red pressure relieve button on the input side of the filter housing, and I would prefer not to, since some crud may get under it and later cause it to leak.)
One final note involves TDS “Total Dissolved Solids”.  Back when I was using one of those drip filter pitchers, it came with a TDS meter.  My water previous to filtering measured 166, and tasted really bad.  After the long wait for that filter to produce water, it did measure 0, and tasted OK.  You were supposed to change the filter cartridge when you got a meter reading above 6.  When the reading was above 6, actually around 10, the water did taste bad again. 
I decided to do some TDS testing on the water from my new filtering system.  I was surprised to find that after filtering, the water measured 158 (as compared to 166 for my unfiltered water).  But the water actually tasted good.  Dong some checking on the internet, and talking with some industry professionals, I found that TDS is not everything when it comes to drinking water.  The carbon portion of my new cartridge was filtering out things that caused my water to taste bad… even though the TDS reading was not as low as with the drip filters, who’s water tasted bad even with a low TDS reading. 
Bottom line, I am happy with the taste of the water coming from my new filtering system, and have a great flow rate, and can replace the cartridge very economically.

The versatility of being able to choose which filter cartridge is best for your situation, allowed me to end up using a different cartridge than the one that came with the housing.  I used:

This cartridge filters out much smaller particles… down to ½ micron, which would keep out many microorganisms and bacteria.   It also has solid block activated carbon, and is effective in removing chlorine taste and odor.  It has a rating of 20,000 gallons at 1 GPM. 
(I would still replace it every 6 months)

It is made by Watts Water – a subdivision of

It is available from:  888-644-6426   for $15.