Reverse Osmosis Water Filters Buyer's Guide
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  We review, analyze and compare the best water filters in the industry including reverse osmosis systems, faucet filters, water distillers, pitcher filters, whole house filters, water softeners, shower filters, bottled waters and more.

Reverse Osmosis Filters - Common Questions & Answers


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A few months back, we bought an RO-9100 R.O. system from Home Depot and installed it. Well, it seems that you get what you pay for, as after being connected for 2 days one of the factory-installed joints (between stages) broke loose overnight and proceeded to pour hundreds of gallons of water into our under-sink cabinet and consequently into our finished basement, causing over $2,000 in damage.

So I went through each joint, tightened them all, and put the unit back into service. A month went by, and a different joint failed while we were at work, again dumping lots of water into our basement. My analysis of the failed joint indicated that even though the fitting was tightened down securely, the tube was not held securely and blew out. It seems as if the joints and fittings are of really poor quality, and will never be up to the task they're required to do. Can you help ?

Robert Ross

Dear Robert: Instead of trying to fix every joint and tighten every fitting yourself, you're probably better off getting a new, better quality system. Because the problem is not that the fittings were not tightened enough; the problem is, as you said, that the parts are of very poor quality (can not seal completely, crack under pressure...). Since the system has broken twice already, I'd doubt the system's integrity and stability. If the system is overall poor quality, changing the parts will not solve the problem -- you're likely to get new leakage, blockage down the road, lots of hassle & costs. I say use it for as long as you can, if it breaks again, then do away with it and get a good quality system.

Generally, we don't recommend buying RO systems from mass merchandisers (Home Depot, Costco) because the systems they carry usually are mass-assembled and imported. The materials used are often cheaper and the systems are not individually tested for leakage & pressure endurance. They'll work fine for a couple of years, then problems often surface afterwards. Good Luck!


I have bought a three stage R.O.. system from a different company. I live in Arizona, it is very hot in the summer. It's currently 110% outside. I installed the RO system in the garage. There is a water softener in front of the RO system. We notice a distinct Plastic smell and taste in our RO water. Please help with any suggestions you may have. I examined our system and have found that most parts on this system are made overseas. Do we need a different type of tubing or housings? Could the temperature in the Garage have damaged the RO membrane and/or made the charcoal filters less effective. This system was installed new.

Jerry Kopeman

Dear Jerry: The 3-stage reverse osmosis system is of an older technology. Their filtering ability is not as thorough as the new 5-stage systems. The membranes used on the 3-stage reverse osmosis systems are the CTA type, which give a contaminant rejection rate of about 80%, while the TFC type membranes used on 5-stage systems give 90%-98% rejection rate. CTA membranes also tend to break down when the input water's pH is either too high or too low. Because there are only 3 stages of filtration, each filter has to work harder, therefore they deplete a lot sooner than filters on a 5-stage system. So if your tap water's quality is bad & demands heavy filtration, then the prefilters & membrane on your 3-stage system will need frequent changing, or they may fail prematurely, causing the weird tastes in the water that you're experiencing.

The distinct "plastic smell" could also come from the storage tank's rubber bladder, or from the plastic housings & tubing.

My suggestion: You can do two things. First, add a carbon polishing filter after the tank, it is usually an inline type of carbon disposable filter, hooked up after the tank and before the dispensing faucet. This filter will usually take out any residual odors from the tank. This is equivalent to converting your three stage system to a four stage. Secondly, you can replace your tank with a new pressurized tank, this usually helps reduce any strange taste in from the tank. All that said, I would recommend to replace your current system with a good quality 5-stage R.O. system that's designed with a TFC type membrane. This will cost you up front, but will save you time, money & hassle in the long run. Filters on a good 5-stage system will last 2 - 3 times longer, saving you money on frequent replacements. You'll get purer and better tasting water -- that's worth a lot! Good Luck!


We recently purchased a house that has an under sink RO system. There are no identifying marks on the tank or filters - and no users guide. It has two vertical filters, one labeled "Pre-filter" and the other "Pre-Carbon," and one horizontal something on top. Also a large tank. There is a sticker that informs that the membrane type is CTA, there is a 10 GPD capacity, and the serial # is 021189.

Oh - the filters do say "Made in the USA." I have no idea when the previous owners last changed the filters and would like to do so now to get on a schedule. The water from the RO tap tastes slightly different from the regular tap, so I'm assuming the filter is doing something, but we're still getting the white discoloration, spots and buildup. Could you advise: is this system sufficient? What type of filters - membranes? - do I use? What would be the advantages of having this RO system and also installing a whole house system? (We get a film in the dishwasher, and the shower/tap leaves your skin feeling .... hard.)

I would greatly appreciate any assistance you can offer! Thank you! in advance for a prompt reply.

Elizabeth Jemison

Hi Elizabeth: Sounds like you have an old industry standard sized ro system, rated at 10 GPD. I think your membrane is bad already, because if the ro membrane is still working, you would get no white buildups (calcium and dissolved solids etc... which is what the membrane's job is to remove).

The water produced from RO tasting different than tap water does not mean that the ro is working, in your case it just means maybe the pre-filter carbon is taking out some smell in the water, or it could mean that all the pre filters are already so old and unchanged, it is affecting the water taste already!!

So what you need to do is change the 2 pre filters and the ro membrane asap. The 10 GPD CTA type membrane is really old, I don't know if you can still find such a replacement. If not, you can upgrade your membrane to higher GPD ones, just need to change the flow-restrictor to match the membrane size.

This system is very basic, a 3 stage system means you have to change the pre-filters very often (6 months vs 1 year with a good 5 stage ro system ), so getting all the filters replaced or getting a new system is your choice. Also CTA membranes are not as good as the TFC kind, so you would need to get a TFC kind if you buy the new membrane, but in order to use a TFC membrane, you would need to make sure the carbon filter is designed as stage 2 on your system (before the membrane, not after the membrane)

Whole house systems are good, works well with the ro for you. But whole house systems should not be used for drinking water(the water is filtered, but not clean and safe to the point for drinking nowadays!), the r.o. is.