The Waterdrop King Tank is a 2.25-gallon stainless steel gravity countertop water filter that removes many common municipal water contaminants.
In our testing, the King Tank removed 100% aluminum, chloroform, fluoride, lead, and more, but a few substances increased post-filtration, and the system has no performance certifications.
What We Like
What We Don’t Like
| Price | $229+ |
| Contaminants Removed | 10+ |
| Certifications | NSF/ANSI 372 |
| Process | Carbon + Ion Exchange |
| Filter Capacity | 3,000 gallons |
| Annual Cost | ~$60 |
| Warranty | 1 year |
Table of Contents
📊 Scoring Data
We test all the water filters we review in our own homes and combine our results with information from the manufacturer’s website and third-party test data to rank each filter across 6 different categories, encompassing performance, quality, value for money, and more. Our scores for the Waterdrop King Tank are shared in the table below.
| Criteria | Results |
|---|---|
| Health Related Contaminants | 9.90 |
| Aesthetic Related Contaminants | 9.90 |
| Performance Certification | Not certified |
| Filtration Rate | 4 GPH |
| Component Quality | Excellent |
| Component Certification | NSF/ANSI 372 |
| Setup | Failing |
| Servicing Requirements | Weak |
| Costs | $0.06/gallon |
| Company | Good |
🎬 Video Review
🚰 Contaminant Reduction
Score: 9.51A big part of our testing is to conduct our own before-and-after water tests to see what a water filter can remove. We tested the Waterdrop King Tank for its ability to remove contaminants in our municipal water in Colorado. We also looked for any performance certifications that the system might have for its contaminant removal abilities.
Our Performance Testing
Score: 9.90
We used Tap Score tests by SimpleLab to test our drinking water quality before and after filtering it through the Waterdrop King Tank.
There were a few things that we did to ensure our testing data was as accurate as possible:
- Before conducting the test, we ran 100 gallons through the system to ensure the filters were already well used.
- When tanking our samples, we followed SimpleLab’s guidelines. This involved filling a large bucket with the water sample, swirling it to ensure it was well mixed, and then collecting the pre-filtration sample directly from the bucket.
- We took the post-filtration sample from the King Tank itself.
On our Tap Score report, we could analyze our test results against a few different water quality standards. We chose to compare our data to Tap Score’s own HGL (Health Guideline Level), which is stricter than the federal MCLs and prioritizes human health.
Health-Related Contaminants
Score: 9.90
We started by evaluating the Waterdrop King Tank’s ability to remove contaminants with health effects from our tap water.
In our unfiltered water, three contaminants with possible health effects were detected above the HGL: chloroform (35.2 PPB), total THMs (35.2 PPB), and lead (0.0006 PPM). There are a few possible health effects of these contaminants, including:
- Developmental effects
- Cancer-causing effects
- Nervous system issues
- Kidney & liver damage
- Immune effects
- Reproductive problems
- Cardiovascular & blood issues
A few other contaminants with possible health effects were detected at concentrations lower than the HGL, including aluminum (0.052 PPM), barium (0.0127 PPM), copper (0.0434 PPM), fluoride (0.1 PPM), manganese (0.01 PPM), strontium (0.062 PPM), and sulfate (10 PPM),
Our post-filtration test results showed us that the Waterdrop King Tank had done a great job of removing 100% chloroform, total THMs, and lead.
The King tank also removed 100% aluminum, fluoride (it uses separate fluoride filters), and manganese, and reduced barium by 40%, copper by 93%, and sulfate by 28%.
Strontium actually increased by 22% post-filtration, and we think this is because the initial 100 gallons of water we used to prime the filters contained elevated concentrations of a handful of ions, which then came out in the filtered water.
We spoke with the chemists at the lab and determined that this effect is likely temporary. We don’t suspect an issue with the filters, but we do plan to perform another test in the future to confirm this.
Aesthetic Contaminants
Score: 9.90
Tap Score sent us a chlorine test strip so that we could test for this contaminant separately ourselves. (Due to chlorine’s volatile nature, it would have dissipated from our water before reaching the lab.)
The test showed that our unfiltered tap water contained around 0.5 PPM of chlorine. After filtering it through the Waterdrop King Tank, it contained 0 PPM of chlorine, telling us that the King Tank had removed 100% of this chemical.
We noted that our filtered water tasted clean, with no chemical tastes or odors. We expected this result given that the filters in the unit are made from coconut activated carbon, which is one of the most researched filters for eliminating bad tastes and odors – this 2013 study concluded that coconut shell carbon “sufficiently reduced” taste and odor problems.
Increase in Contaminants
Aside from strontium, a few other contaminants were detected in increased concentrations in our post-filtered water. Calcium increased by 78%, magnesium by 82%, and sodium by almost 3%. Potassium also appeared where it was absent in the pre-filtration test.
As we mentioned, we suspect that this issue was caused by priming the filters with a water supply that contained these contaminants at higher concentrations, and we don’t think there’s a cause for concern. (These contaminants aren’t dangerous to health in trace amounts anyway.)
View the table below to see all the contaminants removed from our water by the Waterdrop King Tank.
| Contaminant | Measurement | Pre-Filtration | Post-Filtration | % Change |
|---|---|---|---|---|
| Aluminum | PPM | 0.052 | 0 | -100% |
| Barium | PPM | 0.0127 | 0.0075 | -41% |
| Calcium | PPM | 8.8 | 15.7 | 78% |
| Chloride | PPM | 6.9 | 6.4 | -7% |
| Chloroform | PPB | 0.0352 | 0 | -100% |
| Copper | PPM | 0.0434 | 0.003 | -93% |
| Fluoride | PPM | 0.1 | 0 | -100% |
| Lead | PPM | 0.0006 | 0 | -100% |
| Magnesium | PPM | 2.19 | 3.99 | 82% |
| Manganese | PPM | 0.001 | 0 | -100% |
| Sodium | PPM | 10.4 | 10.7 | 3% |
| Strontium | PPM | 0.062 | 0.076 | 23% |
| Sulfate | PPM | 10 | 7.2 | -28% |
| Total THMs | PPB | 0.0352 | 0 | -100% |
| Potassium | PPM | 0 | 1.1 | n/a |
Performance Certifications
Score: 6.00
We know that many folks look for certifications as proof of performance, but we couldn’t find any evidence that the Waterdrop King Tank is certified by the NSF/ANSI, IAPMO, or the WQA.
We couldn’t even find evidence of third-party testing to NSF Standards, which is a real shame – given that it did a great job of removing contaminants from our water, we think Waterdrop is underselling the King Tank by failing to provide this information.
So rather than compare our test results to official certifications, we’ve compared them to Waterdrop’s reduction claims.
Waterdrop says that the King Tank can reduce 98% fluoride, 98.95% chlorine, bad taste and odor, rust, heavy metals, sediment, spore cysts, and “other harmful substances” (we couldn’t find a full list of contaminants removed anywhere).
We’re unable to validate all the contaminant removal claims because not all of these were present in our water, but the King Tank did remove 100% fluoride and chlorine from our water, as well as any poor tastes and odors. It also removed 100% lead and aluminum, and greatly reduced copper and barium (all metals).
| Contaminant | Waterdrop’s Removal Claims (%) | Water Filter Guru Testing Data |
|---|---|---|
| Fluoride | 98% | 100% |
| Chlorine | 98.95% | 100% |
| Bad taste & odor | No Evidence | 100% |
| Rust | No Evidence | Not Tested |
| Heavy metals | No Evidence | 100% |
| Sediment | No Evidence | Not Tested |
| Spore cysts | No Evidence | Not Tested |
Our verdict is that Waterdrop really needs to share some testing data for the King Tank – at the very least third-party testing, but ideally official performance certifications.
🚦 Filtration Rate
Score: 10.00The Waterdrop King Tank has a faster filtration rate than most of the other countertop water filter systems we’ve tested.
We timed how long it took to filter a full batch of water and calculated its filtration rate at 4 GPH (gallons per hour), making it one of the faster gravity water filters of this type.
This was the filtration rate that we achieved with two black filters and two fluoride filters.
📐 Design
Score: 9.40We assessed the quality of the Waterdrop King Tank’s components and looked for evidence of official certifications for design safety and structural integrity.
The Waterdrop King Tank is a freestanding countertop water filtration system. It’s made from 0.8mm thickened stainless steel and has a simple, cylindrical design, with two water chambers: one that sits on top of the other. The chambers are separated by filters, so water gets filtered as it flows from the top chamber into the bottom.
All the components come included apart from the stand, which is an optional extra.
If you prefer a simplistic design without anything super technical, we think the Waterdrop King Tank should appeal to you. It’s essentially just a unit and filters – there are no filter change reminders, water pressure readers, or electrical components. That makes it easier to maintain, although it might not be what you want to hear if you’re looking for a filtration system with all the mod-cons.
Design Flaws & Setbacks
There’s just one issue we detected with the Waterdrop King Tank’s design: water can overflow out of the bottom chamber if you keep filling the top chamber when it’s full.
The good news is that the King Tank comes with a water level spigot, which means you can view the water level in the unit without having to take it apart. Most competitors don’t have this feature or sell water-view spigots as optional add-ons at an extra cost. So we were happy to see that the King Tank comes standard with what we think is a pretty essential component to help prevent overflows.
Component Quality
Score: 9.00
Waterdrop says that the King Tank is made of “thickened stainless steel”, but to us, the steel actually seemed thinner and a bit more flimsy compared to other similar systems. While we thought the steel/glass sight spigot was a nice touch, it still had a plastic dispenser piece, so it wasn’t entirely plastic-free. That’s why we didn’t give it the top score in this category.
Design Longevity
Stainless steel is known for being a durable material, and the Waterdrop King Tank also has seamless welding, so there are no dips or crevices for contaminants or rust to accumulate – more good news for durability.
Our system didn’t rust or corrode during our testing period, but a few customer reviews on Amazon said that there had been some rusting in the tanks. We can’t confirm the legitimacy of these claims since Amazon reviews are easily manipulated.
Certification
In our research, we found the King Tank is certified for material and component quality and holds an NSF/ANSI 372 certification for lead-free materials, certified by IAPMO.
Filter Materials
The black filters in the Waterdrop King Tank are made from coconut shell activated carbon block and pp cotton. From what we can tell, the fluoride filters are made from a resin (no more information is supplied by Waterdrop on exactly what this is, but we suspect it might be a cation exchange resin, which has been proven in studies to remove trace concentrations of fluoride) as well as activated carbon.
Activated carbon and cotton are typically made from natural materials, while resins are generally made from polystyrene polymer. As far as our research tells us, these materials are all safe for long-term use in water filtration devices.
The filter elements have some plastic components, so unfortunately, they’re not a completely plastic-free solution.
⚙️ Setup
Score: 6.50We evaluated the complexity of setup for the Waterdrop King Tank, and how long the process took us.
We didn’t have a good experience with assembly and setup for this Waterdrop model. While we didn’t need specialized knowledge for the job, and the instructions in the user manual were clear, the filter priming process was time-consuming and tedious.
We found it almost impossible to get a seal with the tan priming washer on our faucet, and the blue priming nipple only works with older faucets. You won’t be able to use either priming method if you have a modern faucet, like a spray or pullout faucet.
It took us over an hour to prime all 4 filters, plus 20 minutes to set up the body of the unit. The process was much longer than for some of the other countertop water filters we tested, which had pre-primed filters and could be assembled and used immediately.
🔧 Maintenance
Score: 8.50The Waterdrop King Tank also wasn’t the best countertop water filter system we’ve reviewed for its servicing requirements, but its maintenance costs were lower than average.
Servicing Requirements
7.00
The biggest maintenance task for the King Tank was replacing the filters. We didn’t find this technically difficult, but we had to prime the filter replacements, too, which took a long time.
We also cleaned the whole system regularly (Waterdrop says to do this once a month). We cleaned the chambers in our sink using soapy water – they’re also dishwasher safe as long as you remove all the other parts. We found cleaning the inside of the sight glass spigot tricky, and there are no included tools for the job.
Waterdrop recommends soaking the tanks in a vinegar and water solution to remove accumulated limescale.
Costs
Score: 10.00
We calculated that our ongoing cost per gallon for all the filters in the King Tank was $0.06/gallon. Here’s a breakdown of the cost per gallon of each of the filters:
- Black filters $0.01/ gallon
- White (fluoride) filters $0.05/ gallon
This ongoing spend makes the Waterdrop King Tank one of the lowest-cost water filters to maintain compared to all the similar systems we’ve tested. Generally, similar systems have a cost per gallon of around $0.30-0.50/gallon.
🏢 Company
Score: 8.65We assessed Waterdrop as a company by evaluating its warranty offerings, shipping policy, and returns.
Warranty
Score: 8.50
Waterdrop provides a 1-year warranty for the King Tank against manufacturing defects in materials and workmanship.
If your system becomes defective during the warranty period due to a quality issue, Waterdrop will entitle you to a free return, issue a free replacement, or provide a free repair service.
This is pretty average for countertop water filters, although we’ve seen some manufacturers offering 5-year warranties or even longer.
View the warranty here (if the warranty box doesn’t show, click the “30-day return” icon beneath the product image).
Shipping
Score: 9.50
The Waterdrop King Tank is eligible for free shipping if you select Economy Shipping, and Waterdrop’s products can be delivered to most states, with the exception of Alaska, American Samoa, Hawaii, Guam, Marshall Islands, Micronesia, Northern Mariana Islands, Palau, Puerto Rico, and the U.S. Virgin Islands.
You can upgrade to Standard Shipping (which is free for all orders over $200) or Express Shipping, which costs $12.99.
View Waterdrop’s shipping policy here.
Returns
Score: 8.00
All products sold by Waterdrop are backed by a risk-free 30-day return policy. To be eligible, you’ll need to disassemble and return the product in its original packaging, and there’s a return shipping fee that you’ll need to cover (there’s no restocking fee).
You can even return your King Tank after the 30-day period has passed, which is something we don’t see a lot. There’s just one catch: as well as the return shipping fee, you’ll also need to pay a 10% restocking fee.
Find more information on Waterdrop’s returns here.
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I noticed that here was not any data on Alkaline removal? That is our biggest concern here in Fallon Nevada and would welcome any and all feedback on this matter! Thank you Gary A. Scarborough
Hey Gary, thanks for your comment. Alkalinity is a key measure of a water sample’s general chemistry. Alkalinity measures the capacity of water to neutralize acids. Alkalinity is thus indicative of the stability of a water sample’s pH upon the addition of acid; water with higher alkalinity will maintain a stable pH after the addition of more acid. Water with low alkalinity cannot buffer against such changes and can therefore become acidic and potentially corrosive to plumbing.
What is the pH of your water?