F9K NSF Certified 1-Year Reverse Osmosis Water Filter, Alkaline Remineralization Filters for 6-Stage RO Systems, Without RO Membrane

Super system at this price! We've bought it years ago. Of course, the filters fit. We installed the iSpring reverse osmosis set a few years back. It is well worth it's money by now. Water from regular interval filters tastes good to me, and I am sensitive when it comes to water's taste. Can't drink odd or off tastes without cringe. I like arrowhead though not in ecstasy about it, not ok from plastic bottles stored in hot weather except in emergencies. I like some mountain streams and some wood springs, am ok with occasional, light carbonation - though it won't improve the taste, just change and mask it. We also used different $15-30 test strips on occasion throughout the house and this water's our clean baseline. I hate chlorine taste and feel and do not want more iron or lead or PFAS than necessary, either. There's only so much antioxidants can do for us. So, despite the terrible fact that this system wastes 2x the amount of water you get from it (wish we could rig it so the excess watered our garden or plant) - this is totally worth it to me. I try to meditate when filling a bottle to put in the fridge for the day, it takes about 20 seconds. It's not so bad with just a glass, but it also isn't for the super easily annoyed. Our storage canister, which is slowly refilled with pre-filtered water after you tab out some, is great for two or three people to drink and cook. If you need a lot of water at a time, you might require a larger system. Think of the time saved hauling and trashing bottles, that gives ample patience and glee to the adults at least. Installation is a bit tedious but straightforward enough. And here's a secret superpower: iSpring's customer service is actually super friendly and helpful! After some years the system started dripping (to refill the reservoir) and just didn't stop unless we turned off water. Called CS and they helped us troubleshoot successfully. Yey! If you have no savy at all, get someone to install this for you and set a reminder to replace filter cartridges on schedule. Especially renters profit from the compact and relatively easy system, it takes some space but leaves enough of room under our double sink for two small trash bins and detergents. The shower's got a cheaper filter (which won't waste) and I would NOT drink that water. It's just barely ok on the skin. This water quality's actually impressive given the price of this system is in the low hundreds. Even disregarding eventual medical bills you prevent, you'll save that back financially by just stopping to shop bottled water. We get solid bottles and just refill, wash, refill for up to a year of reusable, high quality plastics or years on end with stainless. Health, economy, even ecology benefit (considering this set lasts us years now and we used to buy plastic bottles, made with a lot of damage to water) - We're very happy.

Works well with no issues. I really appreciate the included push-to-connect fittings, makes the installation much quicker.

I have been running a 6-stage reverse osmosis system for a year, and while RO water is incredibly pure, it can often taste "flat" or become slightly acidic due to the removal of all minerals. I chose the iSpring F9K 1-year replacement pack specifically for the Alkaline Remineralization stage, as I wanted to restore the essential minerals and raise the pH to a more "natural" spring-water level. Filter Quality & NSF Certification • The Build: These aren't generic "knock-off" filters. You can feel the weight difference in the high-capacity sediment and carbon blocks. The fact that they are NSF/ANSI certified provides peace of mind regarding the safety of the materials used (no lead or BPA leaching). • Remineralization Stage (AK Filter): This is the star of the pack. It uses red mineral stones and calcite to add calcium, magnesium, and potassium back into the water. In my testing, it successfully raised the pH of my RO water from a slightly acidic 6.5 to a much more alkaline 8.2. • Carbon Block Efficiency: The 5-micron CTO carbon block is exceptionally dense. I noticed an immediate removal of the slight "chlorine" scent that had begun to creep into my system as the old filters reached the end of their life cycle. Installation & Fitment • Standard Sizing: These are standard 10-inch filters. They fit perfectly into my 10" housings with no "bypass" issues or rattling. • O-Ring Integrity: The seals on the sediment and carbon filters are high-quality rubber. I didn't experience any of the "crimping" or leaks that sometimes occur with lower-tier replacement packs. • Flushing Process: Every carbon filter requires flushing to remove "fines" (loose carbon dust). I ran the system for about 10 minutes, and the water cleared up significantly faster than with previous brands I’ve used, indicating a cleaner manufacturing process. Pros & Cons ✅ Pros: • Comprehensive 1-Year Supply: Includes all pre-filters and the specialized alkaline stage (minus the RO membrane, which usually lasts 2-3 years). • Superior Taste Profile: The remineralization stage gives the water a "crisp" mouthfeel that pure RO water lacks. • System Protection: The high-quality sediment filter does an excellent job of protecting the more expensive RO membrane from clogging. ❌ Cons: • No Membrane Included: As the listing clearly states, this doesn't include the RO membrane. Ensure you check your membrane's age before ordering just this pack. Final Verdict The iSpring F9K is the gold standard for maintaining a 6-stage system. It doesn't just "clean" the water; it "engineers" it for better health and taste. If you value consistent pH levels and want a certified filter that won't leak or bypass, this is a necessary investment for your home’s water quality. Helpful? If this breakdown of the pH levels and filter density helped you, please click the "Helpful" button below!

I've owned two of these units over the past 15 years and they are super reliable at providing great drinking water. Sean and his crew at I-springs always answer the phone and are very helpful with maintenance questions.

I’ve been using this 1 year reverse osmosis filter set for a while and it does an excellent job and keeps the water nice in my 6-stage RO system. The NSF cert is reassuring for knowing the filter quality I can expect, and I have experienced clean clear good tasting water ever since I put these filters in! The alkaline remineralization really does put back some nice minerals and I’ve noticed the water is more tasty than the plain RO filtered water. The filters are well-made and fit perfectly into my system without leaking or any other problems. The only thing that I find sort of a pain is that it’s hard to tell which specific filter is which until you open up the individual plastic bags - some are very similar looking, and the outside packing is not necessarily clear concerning which bag has which filter. It would be much better if they each sealed bag had some clear printing on it of what type of filter is inside it, and the stage number it belongs to. Occasionally, I have to open one up just to make sure it’s the right filter, and that is a bit annoying at replacement time. Overall, each filter works like it should and lasts the whole year as advertised! Worth the price and it was easy to replace. It is compatible with my iSpring 6-stage.

We have had the I-Spring 6-Stage RO for 1 year and we absolutely love it. We would never go back to non-RO water. We use it for drinking, cooking, canning, coffee. We even give the dog RO water :) I recently hooked it up to our fridge so we can get RO ice cubes. Our old ice cubes used to stick to each other all the time even when they were freshly made. As soon as we switched to RO, the ice cubes don't stick and are noticeably better - who would have thought! This filter pack is expensive, but we still think the value is exceptional for this system. You get 2 each of the filters (except for the stage 5 carbon filter because it lasts a year). So that's 9 filters in all - a little less than $10 a filter. The filters all appear well made. The old 1st Stage filter was really gross when I took it out, it had a color between sand and iron. We are SO happy that we did not drink any of that stuff. The flow rate also improved noticeably after the filter swap. I waited an entire year before swapping (you are supposed to do every 6 mo). Next time I will probably do it closer to 6 mo. The filter swap out did take some time. First you have to shut off the valves, release the pressure, unhook the flex pipe, and pull the unit out. I put aluminum foil over the tubes that had the clean water running through them. Remember that the RO water is untreated so it's important to keep contaminants away from the parts that touch the RO water. The 3 tanks on the bottom are very easy to unscrew and replace the filter (provided you have the tool), but the carbon and Alkaline filters are more difficult since you have to unscrew all the connectors, take apart, and then put back together. Again be careful to wash your hands and don't contaminate the last 2 filters. Don't forget to run an entire tank through the new filters before use. Also a general note, don't forget to completely drain the tank when you let it sit idle for a 5 or so days. I've noticed it tends to get an odd taste, which I assume comes from the tank. They also say to refrigerate the RO filter if you will be gone for more than a week. I have not done this yet, but I think I would just throw the whole unit in there instead of removing the RO filter (and place aluminum foil on any open tubes).

I’ve had my system for a few years now and not only is it nice to have great tasting water available at all times but it also improved the quality of my coffee considerably. It’s fast, relatively quiet, and the tank is more that sufficiently sized for a family of 4 that seem to constantly be filling our water bottles. The few times that I’ve had questions or issues, they have been incredibly patient and helpful. Have any questions about your set up or filter change? John will walk you through it.

Perfect fit for our undersink RO, shipping fast. Was a good decision to add this equipment to our kitchen remodel. Per instructions easy to change filters. Comes with new fittings if needed. I didn't use them but was nice that they were in the box. With no leakage. With that they are OEM replacement, functionality Perfect and materials seemed to be well made.

Me gusta la calidad de estos cartuchos de repuesto, además que son más fáciles para cambiar en la purificadora.

خاضعة للمواصفات الامركية انصح بها لمن يبحث عن الجودة 👍

Ho acquistato il set di cartucce iSpring F9K come ricambio annuale per il mio sistema di filtrazione, e la differenza si sente subito. Dopo l’installazione, l’acqua è tornata chiarissima, senza odori e soprattutto buonissima da bere. Il montaggio è semplice e tutte le cartucce si inseriscono senza difficoltà. Anche il flusso dell’acqua è rimasto costante, senza cali di pressione. Per l’uso domestico quotidiano è un kit davvero completo e conveniente, perché permette di coprire l’intero anno senza dover acquistare filtri singoli. In sintesi, sono ricambi affidabili e fanno esattamente ciò che devono: migliorare il gusto dell’acqua in modo evidente.

Je recommande aux personnes dont l’eau potable contient des substances organiques indésirables, l’eau qui en sort est excellente !

I am impressed with the simplicity of changing your own filters. So much cheaper than having water depot people install and service. The water tastes good and I can be confident I am not consuming lead.