Finding the right undersink or reverse osmosis filter can be a serious business.

While the EPA’s Safe Water standards protect us from the most harmful effects of pollution, they still allow low levels of many questionable contaminants.

Even if health risks aren’t a concern, many areas of the country suffer from hard water, which can clog pipes and reduce the lifespan of hot water appliances.

What’s on this page?

An undersink or reverse osmosis (RO) filtration system treats your water quietly in the background, substantially improving one simple but necessary aspect of your kitchen.

Let’s take a look at two of the most popular RO and undersink filter brands: APEC and iSpring.

As a WQA Gold Seal Certified system, you can feel confident in the APEC ROES-50’s ability to remove all of the contaminants listed in its product description. The Water Quality Association has parity with each of the major water safety testing bodies, so a gold seal of approval from them is just about as good as it gets. The iSpring, on the other hand, has not received certification from any of the major independent labs. Instead, it’s listed as meeting NSF/ANSI Standard 58 for reverse osmosis filtering in third-party lab tests.

As two independently verified systems using similar filtering mechanisms, the differences between each model’s filtering capability are negligible. While there are slight differences between their ability to reduce levels of different contaminants (we’re talking fractions of a percent), a look at the customer reviews for the APEC and iSpring show that both do a good job at removing common pollutants, and remain consistent over long term use.

APEC’s reverse osmosis filtering system is heavy on the carbon block elements, with 3 separate carbon filtering stages accompanying a sediment screen and the reverse osmosis membrane. According to the brand, their carbon blocks are designed to capture as much chlorine and as many other organic chemicals as possible, handling up to 50 gallons per day.

Added to the carbon elements is a sediment removal filter to catch dust, particles, and rust, which helps protect APEC’s ‘High Rejection TFC’ reverse osmosis membrane. We appreciate APEC’s Spiral Wound Design, which increases filtering efficiency as well as structural strength. However, we were a little disappointed to see that the pore size of APEC’s membrane filter isn’t listed, with the brand simply saying their system uses ‘Industry standard’ membranes. As the fineness of a membrane is a key indicator of filtering power, this is valuable information to know.

iSpring uses a unique 6-stage filtering mechanism in the RCC7AK. First, a pre-filter screen for sediment and chemicals. Like the APEC, these include a fine screen sediment filter, a carbon block filter, and a granulated carbon (GAC) filter. GAC filters are generally considered more effective at removing chemicals like chlorine and chloramines than standard block filters, as well as some heavy metals.

Unlike APEC, iSpring clearly advertises the details of their Reverse Osmosis (RO) filter stage, using a 0.0001-micron membrane, which is so fine that it captures almost everything larger than the water molecules themselves. After another GAC filter stage, this product finishes with a unique process to restore beneficial mineral salts to the water, with an Alkaline Remineralization filter. This should help combat the unusual taste and texture of pure reverse osmosis water, which many can find slightly offputting.

Read: Everything you need to know about carbon filtering.

There’s not much difference between the base price of the APEC and iSpring. However, a look at the lifespan of their filters does reveal a slight advantage for the APEC. Every ROES-50 is equipped with larger-than-average solid block filters that have a longer lifespan than most other competitors on the market. Depending on the quality of the water source, you can expect up to a year of solid performance from the APEC, versus a 6-12 month range with the iSpring.

Given that both of these systems make use of multiple carbon block stages, the rate of replacement will quickly affect the long-term cost-efficiency of the filter.

With many of us at CleanCoolWater preferring the taste of mineral water, we’re interested in the iSpring’s remineralization stage, offering drinkers the benefits of reverse osmosis filtering without the sacrifice of losing salts. However, the fact that iSpring doesn’t acquire WQA or NSF certification for the RCC7AK is a negative for us,

With its WQA Gold Seal Certification, US manufacturing, and longer carbon block filter lifespan, we think the APEC ROES-50 is a slightly safer bet. Check out the latest price here.

Like their reverse osmosis filter, iSpring tests their undersink model, the CU-A4, to NSF/ANSI standards including all of the tubing and other water-contacting parts. While this isn’t as good as providing genuine certification from the NSF, meeting the leading independent body’s standards is a great sign of quality.

Since neither the APEC nor iSpring undersink models use a reverse osmosis system, they don’t reduce total dissolved solids in water (meaning that you get to keep those beneficial minerals). Both do however contain highly effective carbon and sediment screening stages, helping dramatically reduce the levels of chlorine, lead, and other organic chemicals in your tap supply. These are the principle contaminants you’d expect an undersink filter to handle, and users can feel confident that both models produce safer, better-tasting water when it comes to these common pollutants.

Because the iSpring includes additional filtering elements (see below), it offers an extra level of contaminant removal when compared to the APEC. Here, the iSpring has the edge for removing or reducing levels of bacteria, algae, and other large protozoa.

The iSpring CU-A4 differs from the APEC WFS in that it includes extra stages in its filtering process. While this difference is reflected in the base cost of each product, it does mean that the iSpring is the wider-ranging device. It contains:

The APEC, on the other hand, makes do with just three filtering systems: a polypropylene sediment filter to removes dust and other particles, and two 10 inch carbon block filters to do the majority of the filtering work. While this does restrict the scope of what contaminants the system is able to handle, APEC’s carbon blocks are some of the best around, meaning that it’s extremely effective at reducing levels of organic pollutants.

Both the iSpring and APEC come with chrome faucets as standard, and each has competitive base prices. They also both offer impressive filter cartridge lifespans, with the APEC coming out slightly better at over a year between filter replacements, versus the iSpring’s ‘up to 12 months.’

Differences in value for money start to appear depending on your filtering needs. If you’re mostly concerned with common organic contaminants such as chlorine, then the extra cost of iSpring’s additional filtering stages will eat away at your savings. If you use a private or unstable water source, on the other hand, and are more concerned about microorganisms, then the iSpring may save you from needing to invest in further whole-home or point-of-entry filtering.

These two ‘Amazon Choice’ undersink filters are among the most popular, most effective systems around, and we’d recommend either for those looking for serious filtering power without the drawbacks of a reverse osmosis system.

While we’re not so keen on how the iSpring is listed as meeting NSF standards rather than being officially certified, we are impressed by the number of filtering sections this brand manages to pack into a relatively small system, including an ultrafiltration stage. The result is an efficient filter that can protect your water supply from a wide range of contaminants.

If you’re looking for comprehensive contaminant coverage, then we think the iSpring CU-A4 is the undersink filter for you. Here’s the latest price.

More interested in protecting your tap supply from the most common contaminants in public water? Then, the APEC WFS-100 is a longer-lasting and more cost-effective choice. You can shop the APEC WFS-100 here.