A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the usable life of these two filters is to use a pressure gauge to identify when pressure reaching the membrane starts to decline. This is your indication one or both of the filters is beginning to clog.

Also be cognizant of the chlorine capacity of the carbon block. A good 0.5 micron carbon block for example will remove 99% of the chlorine from 20,000 gallons of tap water presented at 1 gpm. Some original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons. Remember that all the water you process, both waste water and purified water, go through the carbon block.

Regarding your RO membrane and DI resin, use your total dissolved solids (TDS) meter to measure, record, and track the TDS (expressed in parts per million [ppm]) in three places: 1) tap water, 2) after the RO but before the DI, and 3) after the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 ppm. Common readings are 100 to 400 ppm. So for sake of discussion, let's say your tap water reads 400 ppm. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that TDS reading down to somewhere near zero?

If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block (collectively called “prefilters” because the treat the water before it reaches the membrane) do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the “in” port on your RO housing and you'll see it is still approximately 400 ppm.

The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 90% (i.e., they reject 90% of the dissolved solids in the feed water). So the purified water coming from your 100 gpd membrane would be about 40 ppm (a 90% reduction). Filmtec 75 gpd (and below) membranes produce purified water (a.k.a. “permeate”) more slowly, but have a higher rejection rate (96 to 98%). The lifespan of a RO membrane is dependent upon how much water you run through it, and how dirty the water is. Membranes can function well for a year, two years, or more. To test the membrane, measure the TDS in the water coming in to the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce purified water more slowly as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the TDS in the RO water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm, you know that your resin needs to be replaced. Sometimes people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin “dirty” water. This will exhaust the resin quicker than would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal.

Additionally, don’t forget to sanitize the entire system at least once per year, and wash and lube your housing o-rings with food-grade silicone grease every filter change.

We hear this question frequently – and with good cause. There is typically little if any information provided by original equipment suppliers in this regard. Fortunately this is an easy riddle to solve for RO/DI system owners! Filter cartridges (e.g., sediment filters, carbon block filters, GAC cartridges, DI resin cartridges), and therefore the internal dimensions of the housings that contain them, come in only a few standard sizes. The sizes are very different from each other, so you don’t have to worry about making precise measurements of your housings.

Housings are typically designed to accommodate filters of one of the four following dimensions:
• 2.5 inch diameter x 10 inch length
• 4.5 inch diameter x 10 inch length
• 2.5 inch diameter x 20 inch length
• 4.5 inch diameter x 20 inch length

Nearly all residential RO/DI systems used in the marine aquarium hobby are designed to utilize 2.5 inch diameter x 10 inch length filters. Now – one note just to complicate things – you’ll sometimes see filters for these housings that measure 9 3/4 inch or 9 7/8 inch in length – no problem! They will fit just fine in standard 10 inch housings.

Also note that there are filters with dimensions other than those listed here, but there is a very high likelihood your system uses the 2.5 inch x 10 inch filters.

Well, yes and no. New sediment filters can simply be installed, and you're done. As for carbon blocks, RO membranes, and DI resin, that's another story...

Manufacturers recommend flushing new carbon block cartridges for at least 10 minutes before using the product water. Don't run the flush water through the rest of your system. Don’t run flush water through other stages in your system.

Manufacturers recommend flushing new RO membranes for up to 40 minutes to remove preservatives before using the product water. Don’t run flush water through other stages in your system.

Run 1.5 gallons of flush water through new DI resin before using the product water. Avoid contaminating (e.g., bacteria/mold/fungus) DI resin. Minimize storage time. Store DI resin in an airtight container to keep it moist until use. Store unused DI resin in an opaque container to avoid exposure to light. Clear shipping bags are inappropriate for long term storage. Treat your resin gently! If resin is exposed to freezing temperatures during shipping, allow it to warm at room temperature for 24 hours prior to use.

For those of you with chloramine issues, Catalytic GAC should be rinsed thoroughly, then wetted for 12 hours before use.

Yes! Seems like this would be a simple matter of unscrewing the bottom of the cartridge, dumping the old resin in the trash, placing fresh resin in the cartridge, and replacing the cartridge in the housing. Well, almost...

It's how you place the new resin in the cartridge that's important here. First a little background on DI resins.

Remember that the vast majority of folks in this hobby who use DI resin take advantage of mixed bed resin. This resin is composed of small plastic cation beads and anion beads that remove positively charged, and negatively charged ions, respectively. These beads work most effectively when they are thoroughly mixed (which is the way they are when you buy them).

To assure the beads stay mixed together, pack the beads tightly in the refillable cartridge. Fill the cartridge to within a 1/4 inch of full with resin. Now pack the resin by dropping the cartridge repeatedly (~40 times), rubber washer end down, on a hard surface from a height of about 1/2 inch. Essentially what you are doing is bouncing the cartridge to get the resin to settle. You'll see that it settles significantly – likely several inches. Add more resin and settle it again. You'll not see as much settling this time. Now fill the cartridge a third time to within 1/8 inch of the top and pack the resin a third time. If you see any settling at all, refill to within 1/16 inch of the top, replace the cap, and you're good to go! Packed in this way, you'll not see the resin separate over time.

Typically, pressure gauges are installed in reef RO and RO/DI systems so that they read the water pressure in the system after the sediment filter and carbon filter, and before the RO membrane.

This provides some very useful information. First, it will indicate if your home's water pressure is sufficient (or in rare cases too high) for an RO system. In unusual cases the pressure is not high enough and a booster pump will be required. The problems caused by low water pressure may be exacerbated by cold tap water temperature (during winter months, for example).

So you've hooked up your new system, and your pressure gauge indicates you have sufficient water pressure (sometimes referred to as line pressure). What good is a pressure gauge to you now?

If you record the line pressure with new sediment and carbon filters, a reduction in line pressure will be an indication that one or both of the prefilters are clogged and need to be replaced.

So, as a TDS meter allows you to monitor the function of the RO membrane and the DI resin, a pressure gauge allows you to measure water flow through the prefilters.

Buckeye's Premium Series units come complete with a pressure gauge. We also sell add-on pressure gauge kits that are very easy to install.

Assuming your system accepts stand-sized membranes, you can add a higher (or lower) capacity membrane very easily. Pull the old one out, slip a new one in, and flush the new membrane appropriately. You'll also need to replace your flow restrictor. Flow restrictors are matched to the capacity of the membrane, and serve to partially plug the waste line that exits the RO housing. By partially blocking flow in the waste line, they serve to pressurize the RO housing. It’s this pressure that allows the reverse osmosis process to work. So - all systems have flow restrictors.

There are four general types of flow restrictors. The plug-type restrictors are just that - a small plastic cap, or plug with a very small hole that is inserted in the waste line of the RO (sometimes these come inside the fitting at the waste port of the RO). To find this type of restrictor, remove the waste line from the waste port on the RO housing, and look INSIDE the tubing. Remove the restrictor and replace it with a restrictor sized appropriately for your new membrane.

Some systems use a capillary flow restrictor. These restrictors look similar to the plug type, except they have a long, thin (several inches to a foot or so) capillary tube extending from the cap. Again - this type of flow restrictor can be found inside the waste tubing.

A third type, sometimes called block or tube restrictors, look like a short length of 1/2 –inch pvc tubing with a quick connect fitting on each end. Some of these restrictors have an integrated flush valve.

The fourth type of flow restrictor can be used to addresses an operational issue present in most residential RO systems. You've likely heard of the need to maintain a waste water to permeate ratio of 4:1 (ratios between 3:1 and 5:1 are acceptable). You may also have heard complaints from RO owners during winter - My RO production has slowed to a trickle - I can't figure out what's wrong. This is very common. When winter hits and outside temperatures drop, the temperature of your tap water also drops. Remember that RO membranes are designed to operate at capacity at a given temperature and pressure. Filmtec membranes for example are designed to operate at 77 degrees F and 50 psi. If you provide the membrane with colder water, the permeate production will drop dramatically. When it does, what happens to that 4:1 ratio? The ratio becomes skewed towards a much higher waste:permeate value. With an adjustable flow restrictor a simple minor adjustment to the valve can put you right back on a 4:1 ratio. You'll need about 30 seconds and a sharp pair of scissors to install an adjustable flow restrictor.

Manufacturers commonly describe the size of the pores in filters, and therefore the maximum size particle that will flow through a filter in terms of microns. A micron is 1/1,000,000th of a meter or approximately 0.00004 inches. Unfortunately, manufacturers rate filters based upon this pore size without applying a standard technique to express the ratings. Some manufacturers/retailers claim filter ratings expressed using nominal numbers. Others claim filter ratings using absolute numbers. Some round off one or the other ratings. Many (most) don't tell you which rating system they are claiming. For example, a 5 micron absolute filter removes a very high percentage (approaching 100.0%) of particles 5 microns or larger; while a 5 micron nominal filter will remove approximately 85% of particles 5 microns or larger.

This is an easy one, but it is a question we hear from time to time. Push the colored ring on the fitting (the collet) in towards the fitting and pull the tubing out. If the tubing doesn’t come out easily, its likely the collet isn’t pushed all the way in, and/or there is pressure inside the fitting and tubing. Release the pressure by bleeding it off from somewhere else in the system, push the collet in all the way, and the tubing will come out easily. Here’s a link to the John Guest web site explanation: http://www.johnguest.com/step2a.asp

In a word, no. Horizontal DI housings are a design intended to minimize the original cost of the system - you should be prepared for the tradeoffs. Horizontal DI units typically contain 8 oz. to 16 oz. of resin. Typical vertical DI cartridges contain 20 oz of resin. Obviously the more resin contained in the housing the longer it will last and the better treatment it will provide.

Some horizontal DI housings are not refillable - you'll therefore have to pay for a new housing every time you need to replace the DI resin. The cost of repeatedly replacing the horizontal housing will far outweigh any money saved up-front in purchasing the unit.

Perhaps most importantly, horizontal DI housings are a less than ideal arrangement for water treatment. DI resin beds shrink/settle through normal use over their life span. You'll note that a cartridge that was full when new can sometimes have a ¼ inch of empty space in it when fully expended. When DI resin settles in a horizontal housing, it leaves a pathway (of least resistance) along the top of the housing where water can flow while coming into minimal contact with the DI resin.

You’ll note that the output from the DI housing is at the center of the end of the housing. Depending upon how your system is configured, RO water may enter the DI housing in port, fill up the housing until the water level reaches the out port (i.e., fill up the bottom half of housing), and then exit the DI housing. Your RO water has been in contact only with half the resin in the housing.

For purposes of the marine aquarium hobby, consider two items: pore size and chlorine capacity. The smaller the pore size, the greater protection the block offers your RO membrane. Carbon block cartridges with a pore size of 1 micron to 10 microns are common in the hobby. Carbon blocks with smaller pore sizes serve as a backup filter to catch those few particles that make it past the sediment filter. For example, the Matrikx+1 Chlorine Guzzler has a nominal rating or 0.6 microns, and an absolute rating of 2 microns. You'll also see it rated at a 1 micron (the 0.6 microns rounded off). Because your sediment cartridge should be in line ahead of the carbon block, the primary purpose of the carbon cartridge is to remove VOCs - volatile organic compounds, and more specifically in filtration of tap water, what we really want it to do is remove chlorine.

Just how much chlorine will a carbon cartridge remove? The cartridges are rated in terms of chlorine capacity. The Matrikx+1 for example will remove >90% of chlorine from 20,000 gallons of tap water presented at 1 gpm. Original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons.

Yes. You’ll need to install a new flow restrictor that will produce a waste:product water ratio of approximately 4:1. Use your TDS meter to measure, record, and track the tds (expressed in parts per million) in three places:

1. Tap water
2. After the RO but before the DI
3. After the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 ppm. Common readings are 100 to 400. So for sake of discussion, let's say your tap water reads 400. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that reading down to somewhere near zero?

If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block filter do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the in port on your RO housing and you'll see its still approximately 400 ppm.

The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 90% (i.e., they reject 90% of the dissolved solids in feed water). So the purified water coming from your 100 gpd membrane would be about 40 ppm (a 90% reduction). Filmtec 75 gpd (and below) membranes produce less permeate, but have a higher rejection rate (98%). If you measure the TDS in your system after the RO membrane, and before the DI housing, you'll be able to measure the rejection rate of your membrane. A declining rejection rate is an indication that the membrane needs to be replaced.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the 40 ppm water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm to 3 ppm, 5 ppm, and higher, the resin needs to be replaced. Sometimes people complain the DI resin didn't last very long. Usually the culprit is a malfunctioning RO membrane sending the DI resin dirty water. This will exhaust the resin quicker than would otherwise have been the case.

First, you’ll need a way to tap into your home’s plumbing in order to supply water to the system. There are many ways to do this – some require advanced DIY skills like cutting and soldering copper fittings, while others are very straightforward. For those comfortable with cutting and/or soldering copper pipe, a visit to a good hardware store will yield any number of different fittings and valves to go from ½ inch copper pipe to ¼ inch tubing. Buckeye offers a number of options:

	Hose bib adapter: Use this to go from standard ¾ inch garden hose threads to a ¼ inch quick connect fitting. We stock both solid brass adapters, as well as plastic adapters with brass thread inserts.
	BFS-134 Hose bib adapter - $5.79

	Hose bib splitter: Splits a single hose bib into two hose bib fittings. Use in conjunction with a hose bib adapter. We stock zinc, and solid brass splitters.
	BFS-188 Hose bib splitter - $5.50

	Self tapping needle valve: With a few quick turns of the needle valve, you can tap into copper pipe. Avoid using this fitting to turn water flow on and off after the fitting is installed.
	BFS-141 Self piercing needle valve, c-clamp - $4.00

	Reducing Tee: This convenient, quick connect tee is useful when you have access to 3/8 inch copper or plastic tubes, like those that feed many faucets.
	BFS-186 reducing tee 3/8 inch - $3.75

	Inline Under-sink Shutoff Supply Valve: Under most sinks you find a hot water copper pipe and cold water pipe, each ending in a small chrome or plastic shut off valve. From these valves you’ll see tubing extending to the faucet above. To use an undersink adapter, first identify the cold water shut off valve. Turn the valve off. Remove from the valve the cold water tubing that runs to the faucet. Screw the new valve into place. Screw the cold water faucet tube to the top of the undersink adapter. Insert the ¼-inch RO supply tube in the quick connect fitting on the undersink adapter, and turn the water valve back on.
	BFS-270 Inline undersink shutoff supply valve - $10.00

In this hobby we measure Total Dissolved Solids in parts per million, or "ppm." We often try to measure TDS down near 0 ppm. Because this TDS level is so low, we have to keep in mind the sensitivity of the meter used to measure it, and the technique used to measure the TDS.

Nearly any contamination in the sample container will cause an erroneous TDS measurement. Some plastic containers are difficult to get absolutely clean, and although they appear clean, they are not. An easy standard approach is to use a drinking glass as a sample container - use one right out of the dishwasher. Obviously, keep your fingers away from the inside surface of the glass.

Calibrate your meter. Use a calibration fluid generally in the range of the tds measurements you'll be taking. Some meters require a specific tds calibration fluid (e.g., 800 ppm), regardless of the tds levels in your samples.

Be careful with how you take your samples. Let's say you intend to measure the TDS in your 1) DI water, 2) RO water, and 3) tap water. Start with the cleanest of the three - the DI water. After letting the system run for a sufficient period of time that you are sure the tds levels have stabilized (to assure you are not measuring tds creep water), rinse the sample container two or three times with the water you intend to sample, and then fill the sample container with sufficient DI water to take a reading.

Now on to the RO water. The water we are interested in here is the permeate – i.e., the water that has been purified by the RO membrane – not the waste water. Make sure you understand which is which before taking the sample. Most RODI systems other than Buckeye Systems are not plumbed to facilitate taking a sample of the permeate. If that is the case, you’ll need to unhook some tubing – likely where the tubing attaches to the “in” port on the DI housing in order to take this sample. This is inconvenient for many people, and we find that people never do it. They report only the tap water TDS and the DI water TDS. Contact Buckeye if you need guidance regarding installing a couple of extra fittings and tubing to facilitate measuring the TDS of the RO water (permeate). When you take the sample, follow the same procedure described above – use a clean sample container, assure you are not measuring TDS creep water, rinse with the permeate several times before taking the sample, and use a calibrated meter.

Use the same approach to collect and measure your tap water as well.

The amount of pressure needed is dictated by the RO membrane. Factory specifications on our 50, 75, and 100 gpd systems call for at least 50 psi; and on our 150 gpd systems, 65 psi. You might get away with up to 10 psi less than these specifications, but be prepared for decreased performance in terms of how much water the membrane purifies, and how efficiently it performs.

We recommend not exceeding 90 psi. There are components in the systems with maximum operating pressures of 125 psi. At 90 psi you can expect exceptional performance from the membrane. If your line (plumbing) pressure exceeds 90 psi, install a pressure regulator (see www.buckeyefieldsupply.com) to reduce the pressure. If you would like to increase your line pressure (in systems up to 150 gpd), install a booster pump.