iSpring RCS5T 500 whole house RO water filter

iSpring RCS5T 500 whole house RO water filter

iSpring RCS5T 500 Review: The Best Reverse Osmosis Whole-House Water Filter

Many people view reverse osmosis (RO) devices as the ultimate form of home water filtration. We didn’t include many RO systems in our list of the best well water filtration system, as they can restrict water flow rate. However, if we could only recommend one RO filter for those treating well water, it would be the iSpring RCS5T 500.

This system can produce highly pure water on-demand without using tanks, meaning that it’s easy to install, even if you’re short on available space.

With built-in pressure gauges and a 5-stage cycle, the RCS5T’s small size hides its filtering power. Water is sent through sediment and carbon filters to remove particulates and organic chemicals before it’s pushed through micropore membranes capable of capturing the smallest contaminants.

When a filter includes an RO stage, it’s important to consider the pros and cons of maximizing filtering power and sacrificing flow rate. While the iSpring can remove almost all common contaminants, it does have a listed flow rate of just 0.34 GPM. However, we think its innovative dual-flow design helps mitigate serious drops in water flow.

If you’re looking for a tankless RO well water system, reviews suggest the iSpring RCS5T 500 won’t let you down.

Filter stages

Including add-ons

Pre-filter, Carbon filter, UV filter, Water softener
Contaminants reducedSediments, metals, organic solubles, microorganisms, minerals, TDS, flouride, nitrates
Flow rate0.34 GPM
Capacity2 years or 2,600 Gallons per membrane filter (500 Gallons per day maximum capacity)
Reviews4.3 from 190+ Amazon reviews
PriceCheck the latest price

Filter technology

In addition to the main reverse osmosis stage, the iSpring RCS5T includes three carbon filters, each with a different density media to target different organic contaminants. Combined with a pre-filter, these additional stages help to persevere the more delicate reverse osmosis membranes.

Stage 1: 5-micron sediment filter. This stage helps to remove rust, dirt, and other particles that cloud water and damage appliances. 5 microns is a microscopic size that matches the best sediment stages in other whole-house filters.

Stages 2 and 3: activated carbon media. These stages help adsorb organic contaminants–the main causes of bad tastes in well water. The use of both Granular Activated Carbon (GAC) and a carbon block stage increases the number of organic contaminants that the iSpring can handle.

Stage 4: Reverse osmosis filter. In a reverse osmosis filter, extra pressure is applied to the water stream to push it through a membrane made of tiny micropores. The spaces in this membrane are an incredible 0.0001-microns wide, meaning that 99.9% of common contaminants are captured.

Stage 5: Carbon finishing media. This stage helps apply the finishing touches to the water supply as it leaves the filter system, ensuring that any remaining dissolved pollutants are captured.

iSpring RCS5T 500 diagram

Filter stages (iSpring)


Comparing the iSpring RCS5T to the SpringWell and Aquasana systems above is a little difficult because they take such a different approach to well water purification.

The iSpring is definitely a better option if space for tanks is limited, and will remove more dissolved solids than any non-RO system. But it may be less effective when it comes to large particulates and soluble iron. Users will therefore need to balance their in-home needs with the specific quality of their source water.

Likewise, it’s unclear how well the iSpring will handle water taste and smell issues in comparison to the SpringWell ULTRA and Aquasana eq-1000. While the iSpring does have multiple carbon stages, it can’t draw on the big carbon blocks used by the other models.

Many RO systems have a significant negative effect on flow rate due to the way they push water through fine screen membranes. In this regard, the iSpring stacks up favorably to other RO systems, thanks to a dual flow design that allows more water to be filtered at once. This increases the daily capacity of the iSpring to 500 gallons.

A built-in booster pump also increases production by raising the water pressure.

Flow rate

With an estimated flow rate of 0.34 GPM, the iSpring pales in comparison to most of the other systems on this page. As a result, anybody wishing to use this filter for standard household needs should also consider installing a water storage tank to hold pre-filtered water.

Many RO systems have a significant negative effect on flow rate due to the way they push water through fine screen membranes. In this regard, the iSpring does actually stack up favorably to other RO systems, thanks to its dual flow design that allows more water to be filtered at once. This increases the iSpring’s daily capacity to 500 gallons.

Owner reviews (highlights)

iSpring RCS5T 500 on wall

(Verified buyer photo)

  • Clark Reid from 04/17/2018 says: “I have been using the RCS5T for over a year…When we started using the system a little over a year ago the TDS was 25. Now it’s running 45. That’s still excellent and I don’t anticipate replacing the RO membrane until TDS is in the 80s”.
  • Thomas Moak from 04/23/2018 says: “This system really works…I added a 300-gallon holding tank and booster pump…My total dissolved solids (TDS) were 640 before installation. Within a few minutes of operation my TDS was, and still is, 7. My bottled water tests about 15!”.
iSpring RCS5T 500 under sink

Under-sink installation option (Verified buyer photo)

  • S. F. Gordon from 01/15/2018 says: “This is not my first reverse osmosis water filter system. I had a GE Merlin before this. It had leaky valve problems, low water flow, high wastewater rejection and it was noisy. The iSpring has solved all of those issues. The only negative I’ve noticed is that the pump can take a few seconds to kick on when the faucet valve is opened”.

Our verdict

Thanks to its dual flow RO system that produces up to 500 gallons of water per day, the iSpring RCS5T 500 is a tankless system that offers many of the same benefits as its much bigger competitors. If you need a well water filter that can fit into a small space, we think you should consider this one.

That said, there as some inevitable sacrifices that come with any reverse osmosis system. The flow rate can never match non-RO, tanked filters, and the capacity of the whole system will be affected by inlet water pressure and temperature.

Filter cartridge replacements

RO System Replacement Filter (2-year supply) $213.29

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