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reverse osmosis


Reverse Osmosis System Considerations

By David F. Walling


Where do I put the RO system?

The most popular place to put an RO system is under the sink. However this may not always be the best place for it. Remember if the RO is too difficult to service then the service won’t get done. Place the RO in the best place for servicing. The garage or basement are good choices you may need to run some tubing but it will be worth it not having to crawl under the sink to replace the elements on your system. If you are building your home include the RO systems placement into you kitchen design. Tell your builder you are planning on supplying the icemaker with purified water. Your builder may suggest placing the RO under the sink ask for alternative sites and explain why. ROCONN connector systems make placing an RO in alternative locations simple the storage tank can also be located in another location as well. For best flow the RO system should not be any further from the icemaker than 25 feet.

When do I change the filters?

On chlorinated water the TFC 4 stage units will need to have the pre-filter or sediment filter replaced every year but this will depend on tap water quality. The pre-carbon needs to be replaced every 6 months do this religiously it will keep the chlorine in your tap water from destroying your membrane. The membrane can last for up to 3 years but this will depend on how well you follow the pre-carbon replacements. The best way to test a membrane is to use a TDS meter (Total Dissolved Solids) this device will measure the TDS level of both your tap water and the water that your RO unit produces. Membranes that remove less than 85% of the TDS in your tap water should be replaced. The post filter should last up to 1 year but this will depend on the organic content of your tap water. For CTA systems make sure they are only installed on water that has been treated with chlorine or membrane will fail.

Drilling a hole in your sink

If you want to drill another hole in your sink you must first determine what kind of sink you have. In my years as a service man I have drilled through thousands of sinks. Cast iron sinks are thick and will be covered in porcelain you can tell very easily if your sink is cast iron. Look at the underside of the sink and use your hand to knock on it. If it's like knocking on a cinder block wall its cast iron. A porcelain clad steel sink will reveal the sound of knocking on a steel door. Stainless steel is pretty self-explanatory. If your sink is mounted under you counter tops such as with Corian or Granite. Drill a hole into the counter top Corian is very easy to drill through but for Granite you may want to have the people who installed the counter tops come back for this job.

Cast Iron: Use carbide tipped masonry bit. Drill it in stages I will first use a ¼" drill to make a pilot hole then graduate to a ½" bit. I always use strips of electrician's tape over the drill area to keep flaking of the porcelain to a minimum. Do not push the drill through to fast let the drill do the cutting. Place a wet napkin under the drill area inside the cabinet to catch the black dust from drilling this will make cleaning it up much faster. Buy a good drill bit not a $3.00 one buy the $8.00 masonry bit. I would recommend, if you are drilling a hole larger than ½" using a Relton bit. This drill has three different drills, first you make a ¼" pilot hole don't forget the tape first, then using the larger diameter drill that has springs to aid in the cutting of the porcelain so you don't push too hard. The second drill makes the hole in the porcelain only. The last drill is slightly smaller than the second is and it will drill all the way through the cast iron. You can purchase a Relton drill on my website at

Porcelain clad steel: The hardest sink to drill by far. This takes a little more precaution use lot of tape over the drill area. Only use new high-speed drill bits on this type of sink. Again let the drill do the work. If you are making a hole larger than ½" use a relton drill take your time this sink is unforgiving.

Stainless steel: Easy to drill using a high-speed steel bit start with a ¼" bit and next use a ½". If you were cutting an 11/4" hole for an air gap faucet or dishwasher air gap assembly I would recommend using a knock out punch. This is the same type of punch an electrician would use to make a hole in an electrical box. You can purchase our 11/4" punch at

A word about Air gaps

Common problems with air gaps are that food builds up inside the drain from operating the garbage disposal. Any time you separate water from a pipe you get that falling water sound (gurgling). Try a little warm water with some lemon juice to break up the blockage. Make sure the 3/8'" drain line coming from your air gap is as short as possible and runs downhill to the drain. Don't grind up any kind of vegetable or fruit peelings in your disposal they don't grind up well and will plug up your drain. Lettuce is also a bad idea. Do cut up a whole lemon once a month and grind it up in your disposal. This will break down oily ground up food that forms in your diverter tee and will make it smell better. Your RO system runs water to drain every time you take water out of it. The unit will automatically shut off when the storage tank is filled. The built in flow control will restrict the concentrate waste stream across your membrane. The RC4000’s flow control is built into the membrane and gets replaced every time you change the membrane. If you try to turn it off or restrict it further you will ruin your membrane. If you by-pass the air gap you should make sure that the drain line coming from the RO at least touches the bottom of the countertop. If the sink fills all the way to the rim it can run backwards into your RO system contaminating it. By-passing an air gap will eliminate the sound of water running to drain but you will need to be cautious on how far the sink is filled in relation to the drain line coming from the RO.


We have a terrible problem with tap water ice in Arizona. We call them floaties and when company comes if you hand a friend a glass of icewater that looks like one of those little shake up snow scenes they won’t be asking for any more of your water. After connecting an RO up to an icemaker depending on the icemakers age you may still see a noticeable amount of white particles. This is caused by scale left by tap waters contact with the ice tray over a long period of time. The scale needs to be cleaned out of the tray. If it is not the ice will stick to the tray when the ice tray dumps some or all of the ice may remain thus having more RO water dumped over the tray it will soon freeze up the whole icebox. I have been called out for this problem so many times that I began talking about the potential problem to new installs. I have also seen RO cubes with frozen fingers of ice sticking out of them - customers would call about this too 2 days after I had hooked up RO to the fridge. This is caused by dissolved oxygen and other gases escaping the water right before the cube reaches its freezing point. Remember RO water is highly oxygenated. I would recommend after adding RO to use vinegar to clean the icetrays or ask customers to replace them. RO ice freezes harder than tap water ice and will last longer in the glass than tap or well water ice. Another problem exists with ice machines this occurs right after an RO is installed. The icemaker is not turned off after the RO is first turned on. Since the RO storage tank is empty only a limited amount of purified water is available to the icemaker. Sometimes the ice machine will freeze up because there isn’t enough water available to the tray when it is first activated. The way to avoid this is to turn the icemaker off until the RO has been flushed out and has completely refilled usually the next day.

Don't grind up any kind of vegetable or fruit peelings in you disposal they don't grind well and will plug up your drain. Lettuce is also a bad idea. Do cut up a whole lemon once a month and grind it up in your disposal. This will break down oily ground up food that forms in your diverter tee and will make it smell better.

Disinfecting an RO system

I recommend sanitizing the R.O. system at least once a year. The best time to do this is while changing your filters. First, shut down the system in the same manner as with a Filter Change. Drain the system, including the tank, and then disconnect the blue tubing from the tank shut-off valve. Put ¼ to ½ teaspoon of household bleach into this tube, using an eyedropper for best results. Reconnect the blue tube to the shut-off valve and follow normal start-up procedures, including draining the tank. If you have an icemaker hook-up installed, be sure the ball valve in the line to the refrigerator is in the closed position during this procedure. If you would like to disinfect the icemaker line then leave the icemaker valve open but remember to throw the next 6 hours of ice out. The air pressure of the tank should be checked at this time with the tank empty. The standard 3.2 gallon RO storage tank will use 7 1/2 psi to displace all the water inside. Use a low-pressure tire gauge to check the pressure if you need to add air use a bicycle tire pump an air compressor can destroy the bladder inside if overfilled. Check the storage tank pressure every time you change the membrane.

A Word about well expansion tanks

If you are getting air trapped inside your pipes inside your home from your well expansion tank then the bladder inside it may have failed DO NOT DRINK THE WATER the following is how to check the tank.

The only way an expansion tank can drain is for air behind the bladder to push it out. If your tank does not drain completely than it does not have enough air in it to displace the water inside. You should be able to easily move the tank empty. Replace your tank every 10 years this holds true for the RO expansion tank as well.

To drain a well expansion tank

First you need to drain the tank as far as it can go by itself. Next using a bicycle tire pump fill up the tank only until the water begins to flow out. Do not over pump the tank or you may ruin the bladder. Keep doing this until you are sure all of the water is out of the tank. Now to obtain the proper air pressure this can only be checked with the tank empty. Fill the tank up with 2 psi below the start of your pressure switch. (Example 30 psi on means 28 psi in the tank.) If the tank will not hold this pressure then the bladder has failed.

Now it would be a good time to disinfect the tank with some bleach. Use an empty filter sump housing to introduce about a 1/4 cup of bleach into the tank you will need some valves to do this. Now rinse the tank by filling it and draining it several times.

One more thing

Most maintenance of RO systems is common sense if you take care of this unit it will take care of you. Not servicing an RO system is certain death for it the RC4000 is the easiest RO to service that I have ever seen there is no reason this unit won’t last the normal household for greater than 10 years. For problem water replace your elements more often and you should have no worries. If you have any questions regarding service please call 1-800-617-1474 we will be happy to help you with any water treatment problem you are having.

David F. Walling has been in the water treatment industry for 16 years and has extensive knowledge about residential and commercial reverse osmosis systems.

For more information, please contact R/O CONN at (602) 432-5402 or fax (602) 942-1451. Or you can E-mail us at

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