Knowledgebase > Setting Up a Reverse Osmosis (RO) or Reverse Osmosis/Deionizing (RO/DI) Tap Water Filter by Keith MacNeil, a Marine Depot Staff Member
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Q11030 - HOWTO: Setting Up a Reverse Osmosis (RO) or Reverse Osmosis/Deionizing (RO/DI) Tap Water Filter by Keith MacNeil, a Marine Depot Staff Member


Before we get into the actual setting up of your RO or RO/DI filter we should go over a couple of basic FAQ's people might have about their systems:

What does an RO or RO/DI system do? RO and RO/DI filters will help in the removal of impurities from your tap water such as chlorine, chloramines, pesticides, phosphates, heavy metals and many others. These impurities may contribute to the growth of nuisance algae, while others can cause even larger problems.

How does the water flow through the filter? While there are many different set ups for RO and RO/DI systems, most standard systems will have 2 or 3 vertically arranged cartridge filters along with an RO membrane housing that lays horizontally. The tap water will first enter the filter and go through the sediment cartridge and then through a carbon block filter. These two filters help remove sediments, chlorine, pesticides*, and cyrptosporidium and Giardia cysts*. From there the water travels to the RO membrane housing to be further filtered. The Captive Purity RO membranes will remove 96% of nitrates and up to up to 99.5% of silicate from the water. The water then exits the RO membrane housing from two different ports, one is the product water and the other is the waste water. For a standard RO unit, this is all the water filtration that will be done, but for RO/DI units the product water is then run through a DI resin cartridge for further water purification.

0.5 Micron Carbon Block
0.5 Micron Carbon Block


How does an RO membrane work? The RO membrane is a semi-permeable membrane. When water is forced to pass through the membrane the impurities and undesirable contaminants are trapped by the membrane allowing the water molecule to pass through. Most of the impurities and contaminants are then trapped within the membrane and will exit with the waste water.

How often should the cartridges and membranes be replaced? The quality of the cartridge and membrane, the amount of water made as well as the quality of the tap water will be the main determining factors. But in general the sediment, carbon block and DI filters should be replaced about every 6 months. The RO membrane will last at least 1-2 years and the use of a flush valve can double that length. Manual inspection of the cartridges, using a color change DI cartridge and the use of a TDS meter are also very handy ways of determining when to change the filters.

What does GPD stand for? GPD stands for Gallons Per Day. RO and RO/DI systems are rated by how many gallons per day they can produce. This is controlled by the flow restrictor normally located in the waste water line where it connects to the membrane housing. You will find systems that will make less than 10 GPD's to systems that make well over 100 GPD and everything in between. If you have a system that has a rating of 60 GPD, that system can make up to 60 gallons of purified water in a 24 hour period of time. The tap water pressure, purity and temperature as well as the age of the cartridges and membrane will all play a role in the actual water production.



Setting up your RO or RO/DI

Once you have purchased your filter and have inspected it to make sure everything arrived undamaged and no parts were missing, you can then start the hook up process. I will start with a condensed version and then try to explain the steps with a little more detail and pictures.

Step 1: Find location for installing your filter system. You will need a location that has a source for cold water and a drain. Connect the filter to the source water and run the waste water line to the drain.

Step2: Install sediment, carbon and RO membrane into their respective housing. Turn on the water. Flush the system of the first couple of gallons. Double check for leaks at this time as well.

Step 3: Shut the water off and install the DI resin cartridge.

Step 4: Turn the water back on and start collecting your purified water.

Seem too easy? Well actually RO and RO/DI systems are fairly simple to hook up and really almost anyone of any level in the aquarium hobby can hook one up. While some set ups may be a little more advanced and/or require a little plumbing work, most standard RO and RO/DI filter installations take only 30-60 minutes tops.

Step 1 (in detail). Location: Determine where you will hook up your filter. Keep in mind that you will need a cold water source as well as a drain. This can be places like a laundry room, under or next to a sink or outdoors near a faucet. If you are hooking your filter up outside it needs to be protected from the heat and cold. Too warm of temperatures can ruin the RO membrane and freezing temperatures can cause the housing to crack. For my system I have a utility sink in my basement with an extra cold water faucet I will use. The filter housing bracket allows me to hang the unit on the wall as shown in the picture.

RO/DI housing mounted on the wall. To the left is the source water for the RO/DI filter, a ¾" spigot and a ¾" garden hose adapter
RO/DI housing mounted on the wall. To the left is the source water for the RO/DI filter, a ¾" spigot and a ¾" garden hose adapter.


There are many different ways to tap into water sources for your filter if you don't have a ¾" male threaded faucet fitting available. You can tap into your copper piping using a saddle valve, use a standard Faucet Adapter or use a Feed Water adapter. If you are unsure what would be best for your situation, please contact our tech support for further assistance.

If you don't have an open drain to allow the waste water to flow down, you can use a drain saddle adapter to tap your PVC drain line from your sink.

Step 2 & 3 (in detail). Installing your cartridges and membrane: Now that you have your filter housing in place, you can start installing the cartridges and membrane (keeping in mind the flow of the water through the filter). For my system the tap water enters the right canister first, so that is where my sediment filter will go.

Sediment filter in place. The blue tubing on the right is where the water will first enter the RO/DI filter, it hasn't been hooked up yet though.
Sediment filter in place. The blue tubing on the right is where the water will first enter the RO/DI filter, it hasn't been hooked up yet though.


The next filter housing the water flows into is the middle chamber where the carbon block filter will be. You will want to use the filter wrench included with your filter to tighten all of the canisters very slightly or simply hand tighten it. DO NOT over tighten as you can crack the housing or canister:

Installing the carbon block filter. Do not over-tighten the canister as it may crack. Hand tightening many times is enough pressure.
Installing the carbon block filter. Do not over-tighten the canister as it may crack. Hand tightening many times is enough pressure.


Next you will install the RO membrane into the RO membrane housing. You will need to start by removing the membrane housing cap and RO tubing running into the membrane housing.

Cap has been unscrewed and removed from the RO membrane housing.
Cap has been unscrewed and removed from the RO membrane housing.


Once the cap is removed you can then insert the RO membrane itself

The end with the small rubber o-rings will go in first.
The end with the small rubber o-rings will go in first.


RO membrane almost fully in place.
RO membrane almost fully in place.


At this point you will need to apply a little pressure to get the membrane fully into the housing so the membrane and housing are flush. You can then screw the cap back on and reconnect the tubing.

RO membrane fully seated in the housing.
RO membrane fully seated in the housing.


Screw the lid back on and reconnect the tubing.
Screw the lid back on and reconnect the tubing.


If you have an RO filter you are now ready to start making water after you have flushed the system (see next paragraph). If you have an RO/DI filter you will still need to add the DI resin cartridge to the third canister.

RO membranes need to be flushed before using the product water. Most manufacturers recommend flushing the system of the first couple of gallons of water produced (dumping both the product water and waste water down the drain). To help prevent the premature exhaustion of your DI cartridge, it is recommended to run your RO/DI system without the DI cartridge for this initially flushing. Install the DI cartridge canister without the DI cartridge in it.

Turn your source water on and test for leaks on your system while you start the flushing process.

As you can see from the built in TDS meter on my system, during the flushing process it was reading some dissolved solids coming out of the system. Once I had made the initial 2-3 gallons of product water to be dumped, I installed the DI cartridge in the empty canister on the left side and the system is now ready to produce purified water for my aquarium.

During the flushing of the RO membrane, note the lack of DI cartridge in the left canister.
During the flushing of the RO membrane, note the lack of DI cartridge in the left canister.


After the flushing of the RO membrane, DI cartridge in place and a zero TDS reading.
After the flushing of the RO membrane, DI cartridge in place and a zero TDS reading.


Step 4 (in detail). You should now have an RO or RO/DI system that is producing purified water for use in your aquarium. From here you have a couple of options of where to collect or deliver your purified water to. You can fill containers or water jugs with the water by manually turning the system on and off or you can add a Float Valve Kit to a vat or your sump for auto replenishment of water. If you have any questions on how to hook up a float valve kit to either a vat or for auto-replenishment of your tanks evaporated water again please feel free to contact our tech staff for assistance. As well on our website you can find some diagrams of different set ups using the Kent Marine Float Valve Kit.



How to change your cartridges and RO membrane

As mentioned in one of the FAQ's in the opening your sediment, carbon and DI resin cartridges will need to be changed about every 6 months (this may be longer depending on source water quality and actual gallons made) and your RO membrane every 1-2 years (longer with the use of a flush valve). But once you have determined it is time to change them out here are the steps on getting it done.

Removal and replacement of your sediment, carbon and DI filters:

Step 1: Turn off your source water. Relieve the pressure if your water filter has one.

Step 2: Unscrew the canisters from the housing using the wrench that came with your filter.

Step 3: Discard your old cartridges and rinse the canisters. You can use a very mild bleach solution to do this or simply given them a good rinse and wipe them down. If you use bleach make sure to rinse them well with hot water.

Step 4: Insert your new cartridges and re-install the canisters on the filter housing. Hand tightening is best to avoid cracking the housing or canisters. If you use the filter wrench, just give a slight turn.

Step 5: Turn your water source back on and double check all fittings to make sure they aren't leaking.

Removal and replacement of your RO membrane:

Step 1: Turn off your source water. Relieve the pressure if your water filter has one.

Step 2: Disconnect the tubing going into the RO membrane housing and unscrew the cap.

Step 3: Pull out your old membrane (may need a pair of pliers to get a good grip of it) and discard. Rinse out the housing thoroughly with hot water.

Step 4: Insert your new membrane like you did when you first set up the filter. Double o-rings go in first and then once aligned inside the housing apply a little extra pressure to push it in flush.

Step 5: Put the cap to the housing back one and re-connect the tubing.

Step 6: If you have an RO/DI system, remove the DI cartridge and reattach the canister it was in. Turn on your source water, check for leaks and discard the first 2-3 gallons of product water.

Step 7: Reinstall the DI system if applicable.

Occasionally flow restrictors will break and may need to be replaced. If you find that after replacing your RO membrane you are getting very little product water and/or more than normal waste water you may want to replace the flow restrictor as well. The flow restrictor and GPD rating on the membrane should match.

Hopefully this article helps with the set up and routine maintenance of your RO or RO/DI system. As mentioned there are lots of different RO and RO/DI systems out there and many different ways to put them to use. If you have any specific questions about a system, how to hook one up or any of the additional features offered for RO and RO/DI systems feel free to contact us any time.


15% off all your replacement sediment filters, carbon filters, DI cartridges and membranes FOR LIFE
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Approved Comments...
For well water users having hard water, there is no way the DI resin will last "about a year", as mentioned in the video. My well water has about 280ppm TDS, and about 19ppm, after the RO membrane.I need to change my DI resin after every 50 gallons of produced water to maintain my 0 ppm TDS. This is by far the most costly factor in running a RO/DI system.Just thought folks might want to know. Approved: 7/22/2012
More explination od what the DI does would have been great. All in all it was good article. Approved: 7/20/2012
Great info. Approved: 7/20/2012
I need more information on efficiency of waste water generation, as I want to collect this water also for gardening or water for the goats. Approved: 7/20/2012
Awesome article & videos. Being new to RO/DI systems, they showed me all the basics in a straight forward manner. Thank you! Approved: 10/10/2011
Informative, Concise, and detailed with necessary links, and unnecessary information provided in link form (for those of us who DO and DO NOT need that information). I thank you. I wont rate down for it, but suggestions of price ranges, and brands for different levels of hobbyists would be nice. Such as I started and have a 40 and 55 gallon Cichlid setup. I have bred a few different species successfully and have committed to a custom 500 gallon tank and the plumbing in finishing out my basement and the cabinetry involved so these would be two totally different setups and needs. Approved: 2/26/2011
Straight forward answer to the problem; quick and easy solution; step-by-step implementation of the product with picture and instructions for setup. Approved: 2/25/2011
I replaced the old self contained membrane/housing with a new unscrewable housing with a replaceable membrane. I wanted to make sure the tubing/plumbing was identicle. I still dont know. I can figure out what end of the membrane to stick in the housing. If not, it only takes one picture. Approved: 7/24/2010
Excellent! The instructions with my 4 stage RO/DI where simply which filter belong to which cannister. No instructions on the membrane installation, or the initial flush without the DI. Thanks for the excellent pictorial, well done. Approved: 7/22/2010
exactly what i needed to know. very detailed. thnx Approved: 2/25/2010
Very well explained with step by step photos. Even I can understand it. Approved: 2/14/2010
I have been debating on purchasing a RO/DI filter. The article talked me into purchasing one. I would like to see additional information on replacemetn filters for RO/DI units. Are all the replacement filters interchangeable between manufacturers? What do the different types of DI filters do? EDITORS NOTE: Most replacement cartridges are interchangable. Please contact us at customercare@marinedepot.com for more information about the different DI cartridges. Approved: 2/11/2010
hooked up my ro/di about 1 year ago and this article is right on point...thanks Approved: 2/10/2010
The article was very helpful. I have a 4 canster RO/DI system. So,How do you setup the pump to a RO/DI system? Also, How to hookup and read the TDS meter. EDITORS NOTE: Please contact us at customercare@marinedepot.com and we will be able to assist you. Approved: 2/8/2010
The article was very helpful. I have a 4 canster RO/DI system. So,How do you setup the pump to a RO/DI system? EDITORS NOTE: Please contact us at customercare@marinedepot.com and we will be able to assist you. Approved: 2/8/2010
The only thing that the article does not address is the amount of waste water that is lost as a result of making RO water. It would be nice to address the ratio between the two. That way a buyer can be totally informed. Approved: 2/6/2010
Im smiling at the timeliness of this..... I just ordered a SpectraPure RO/DI unit from you (to be delivered on Monday), and then I get this email telling me (and everyone else) how to set it up. Talk about great customer service!!!! Well written and nicely illustrated. Thanks! Approved: 2/6/2010
pictures, clear language Approved: 2/5/2010
Article Details
Created on 2/3/2010.
Last Modified on 7/18/2012.
Last Modified by Dot Yuson.
Article has been viewed 37753 times.
Rated 8 out of 10 based on 124 votes.
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