Waterdrop ALK35 Alkaline Undersink Water Filter, NSF/ANSI 372 Certified

I’ve been very happy with the Waterdrop ALK35 filter. I added it to my reverse osmosis system to complete my water filtration process, and installation was simple, just take your time and make sure the tubing is cut clean and straight. What really impressed me is the taste. The remineralization filter adds back beneficial minerals like calcium, magnesium, sodium, and potassium, giving the water a crisp, refreshing taste that reminds me of premium bottled water. The best part is knowing I’m getting great, tasting water without constantly buying plastic bottles or worrying about microscopic nanoplastics. For me, the ALK35 was the perfect finishing touch to my RO system.

So far so good

Worked really well with Waterdrop RO systems. Easy to install and it can fit both 1/4" and 3/8" pipes. One suggestion, please do provide two 3/8" locks. It only comes with three 1/4" locks. For 3/8" fitting, two 1/4" locks and two 3/8" locks are needed.

I purchased this as an add on to my existing, 3-stage, undersink RO system to improve the taste of the filtered water. Acutally it was the lack of taste that I wanted to improve. This filter does improve the taste of the water but it took a couple of days of ussage for it to kick in. Considering this is an "on-demand" type of filter, I don't understand why the improvement took a couple of days. Perhaps the filter needs to reach a saturation point before it is fully functional. I deducted one star due to the poor hardware that comes with it. The unit comes with two 1/4 to 3/8 inch adapters but the locking clips supplied are for 1/4 inch tubing. There is nothing stating whether or not locking clips are needed for the 3/8 inch side. I had some spares so I used them but it would be nice to know whether or not they are needed. The unit also comes with a low quanity mounting clip that uses a single screw. The plastic is too weak to hold the filter so it constantly falls out. The central, single screw allows the clip to rotate which also contributes to the filter falling away from the clip. I added a couple of screw mounted zip ties that hold the unit in place but they will need to be removed every time the filter needs to be changed. The label states it should be changed every six months but I've only had it two weeks so I don't know whether or not it will last six months.

Already have the under sink system - this is just another feature with minerals

This was a great addition to our waterdrop. I also use a pure copper bottle to prep my daily water the night before. The taste has been greatly improved by all 3. Now my water is delicious!

Significantly overpriced for what it delivers. There’s no reason this should cost this much. My RO water measures around 5–10 TDS, and with this filter it only increases to about 18–25. That’s a very marginal improvement at best. Yes, it does improve the taste. Installation is simple. It has never leaked nor reduced water flow. But the performance doesn’t justify the price. Better than cheaper alternatives? Yes. Worth the money? No.

Drops ppm to spring water level! Also, be advised that Amazon AI gives bad information - A mounting bracket and blue clip locks are included with the filter. It’s easy to install, just get a clean straight cut on tubes, snap in and lock with blue clips.

Instantly noticed the change in water quality.

I bought this filter back in July 2025. This is a late review. As this filter was very easy to install there are a few concerns I have about it. 1. Customers service number works but the customer service will for sure mislead you. Fact. 2. It does not up your PH whats so ever. I know this as I went back to work for a water filtration company again. We tested it. Its just plastic with stuff in it. 3. It states it certified. I fact its not. Only there units are. 4. The web description states its certified thats not at all true. 5. Anyone with a 5 star review has no idea what there talking about. I have been in the water industry for over 25 years and I know for a fact that this is just weight in your Revirse Osmosis system. I suggest you looking elsewhere like you local water distributor that sells water and water dispensers. No not walmart. PH filter are special and must have the certificate sticker on it 100% This filter is an absolute joke and not worth the money. It's a scam 100%