Upgrade Our Galley: Why Waterdrop Ultra Filtration is a Must-Have for Sailboats

Waterdrop UF Filter on SV Cadence - The Foster Journey

This week, we installed a Waterdrop 10UA-UF ultrafiltration water filter on our sailboat – and we love it! This post is not sponsored, it’s just our honest review paired with a few affiliate links.

Sailing the Chesapeake Bay since around September 2023, we’ve found ourselves at the dock for most of the winter – drinking city water from our water hose or buying jugs of purified water. Not good. That’s where the under-the-sink water filter comes in.

Jugs are nearly impossible to carry on our new scooters, and when you don’t have grocery deliveries, you’re stuck with water hose water, yuck.

You can taste the rubber, plastic, and metal. It’s difficult to stay hydrated without pure water.

About the New Water Filter

A super simple device that is about a foot long and fits nicely under our sink. It took 5-10 minutes to install. We drilled to screws to hang the filter, and with two wrenches, attached the hoses.

UF Filter on Cadence. UF Stands for Ultrafiltration, a type of water filter that takes out metals, chorine, tastes, and odors.

Waterdrop UF 0.01 μm Filter Stats:

  • Filter Type: Polyester membrane Ultrafiltration (UF) membrane Activated carbon block KDF
  • Filter Purpose (According to the Company): “Reduces the contaminants such as chlorine, taste and odor, sediment, rust, and other heavy metals.”
  • Filter Pore Size: 0.01 micron
  • Size: WD-10UA-UF: 3.6″ * 3.85″ * 12.3″
  • Price: $50-$70
  • Link to Amazon >>

Everything fits perfectly to our existing sailboat plumbing with no need for adapters.

We plan on changing the filter every year, but it claims to work for 10,000 gallons. It’s only installed on our galley sink for drinking, so we’ll be well under the 10k gallon limit when the year’s up. The filter costs less than a hundred bucks and the taste is great!

But don’t worry, we ran tests to see if it actually does anything.

Water from the Marina and Water Filters on Cadence

Our full system when at the dock includes a water filter on the hose just before going into our tanks.

Using an RV Filter on a Sailboat is a good start to pure water.
Using an RV Water filter on a sailboat is a good start to having great-tasting pure water.

But let’s face it, there’s only so much an RV filter can do. Some RV filters don’t have their pore size in microns on the filter. Most are about 100 microns. We’re not sure what ours is. We just grab whatever is available. Here are two kinds we’ve used in the past.

Plus, who knows what’s in the water tanks? Even though we clean them every year with a bleach cycle, it still tastes like water hose.

Now, our system for filtering marina water on our sailboat includes:

  • RV Filter Outside. the RV filter just before entering the tanks to take care of the heavy metals and some taste from the marina water. This filters all water in our tanks.
  • UF Filter Under the Sink. This is our new Waterdrop UF filter mounted under the sink. It only filters the cold water on our galley sink.
After adding the new Waterdrop filter, we have two water filters to purify the marina water.

Testing the Water from our New UF Filter

We measure total dissolved solids (TDS) in parts per million (PPM) when we use our watermaker. The “watermaker” is a desalinator. It’s a reverse osmosis machine that turns saltwater into drinking water.

TDS is not the end-all of water testing, but we figured it would give hard data on the new water filter.

The UF filter does not claim to reduce TDS. In fact it expressly states a UF filter will not reduce TDS – an RO system is designed for that.

But I figured we’d run the test any way and see what happens.

Taste Results from the New UF Water Filter

We’ll get into the PPM data below, but first the biggest difference in this galley upgrade – taste.

The difference was drastic!

Our water before installing the Waterdrop filter tasted like water hose. A gnarly blend of city water + rubber + metal.

After installing the Waterdrop 10UA-UF filter, the water tasted…clean. Just like you’d expect from bottled water.

But it didn’t taste sterile like it does from our RO watermaker. That water tastes straight, H20. This water is a bit softer.

PPM Results from the Waterdrop 10UA-UF

Here’s the first test with our new waterdrop filter.

Comparing sailboat drinking water from tank versus using an undersink ultrafiltration from Waterdrop.
Left: no filter, Right: Immediately after installing the new filter

The glass on the left is water from our tank before the filter.

The glass on the right is water after installing the new filter.

We only ran the filtered water for about 30 seconds before this test. The water was cloudy and eventually cleared with thousands of air bubbles stuck to the side of the glass.

The bubbles were strange, but kind of expected. There’s a charcoal stage in the filter, and we expected to see black particles from that. That’s typical when using a filter like a home Brita pitcher – which we previously used for drinking water.

But nope, there was no residue from the charcoal stage in this filter. Here’s what we found for PPM using our TDS device.

Sailboat Tank Water with RV Filter366 ppm
Tank Water with RV Filter + Undersink UF Filter367 ppm
Total Dissolved Solids
Measuring Drinking Water with a TDS tool on a sailboat.
This is the water before the new water UF filter. It’s from our tanks with the RV filter on the water hose.
Testing TDS on sailboat drinking water.
TDS of 367 is well under the 500ppm recommended safe level.

A TDS tool jumps around from 360 to 363 to 367 when you swirl the water or move the tool. I’d bet there’s a 98% confidence level in the data.

We ran the water through the UF filter for an additional 120 seconds and poured a third glass. This time, there were no bubbles. Just crystal clear pure water.

Waterdrop Ultrafiltration Tests on a Sailboat
1: Water hose water, 2: Immediately after installation of Waterdrop, 3: After running water for 2 minutes

Here are the ppm results after pouring the third glass.

Comparing ppm for RV Filter vs Waterdrop UF Filter on a Sailboat

Why did water TDS PPM go up after just sitting for 10 minutes?

It’s curious, isn’t it? There are two explanations.

  1. Outgassing. Water naturally absorbs carbon dioxide (CO2) from the air. This CO2 can slightly affect the PPM reading. When the water sits still, some of the dissolved CO2 might slowly escape back into the air. This outgassing could cause a slight decrease in total dissolved solids (TDS), which some meters measure and report as PPM.
  2. Margin of Error. Most meters used for home water testing have a certain level of sensitivity. This means they might not always give a perfectly precise reading every single time you test. A small fluctuation of 10 PPM could be within the margin of error for the meter itself.

It’s less likely TDS instrument margin of error because it went up for both glass 1 and glass 2.

Either way, 10ppm is not that significant.

Let’s dig a little further in the UF filter and share a few reasons why we chose this filter over others.

What is an Ultrafiltration Water Filter?

An ultrafiltration (UF) water filter is a type of system that uses pressure to purify water through a special membrane. Here’s a breakdown of how it works.

  • Pressure-driven process: UF relies on your home’s regular water pressure to push water through the filter.
  • Semi-permeable membrane: The key component is a semi-permeable membrane with tiny pores. These pores are much smaller than a human hair, typically ranging from 0.01 to 0.1 microns.
  • Straining out impurities: As water gets pushed through the membrane, it separates contaminants like:
    • Bacteria
    • Viruses
    • Parasites
    • Other suspended solids like dirt and silt
  • What stays behind: These larger contaminants get trapped on the membrane surface and aren’t allowed to pass through.
  • Clean water comes out: Meanwhile, the clean water, along with dissolved minerals, flows through the membrane pores on the other side. This filtered water is what you end up with.

Water Filter Type Comparison, UF vs. RO

Here’s a key difference between UF and another popular filtration method, reverse osmosis (RO).

UF vs. RO pore size: UF membranes have larger pores compared to RO membranes. This means UF allows some dissolved minerals to pass through, resulting in water that retains its natural taste.
RO filters out more: On the other hand, RO membranes have much finer pores, filtering out a wider range of impurities, including dissolved minerals. This can sometimes lead to slightly bland-tasting water.

Overall, UF is a good option for removing harmful contaminants while keeping the beneficial minerals in your water supply.

It’s not going to serve as big of a purpose when we’re on anchor using our RO desalinator, because the RO water is damn pure…almost too pure. But the UF filter will help us purify any contaminants or tastes in our tanks.

I’m curious to see how it works when we use the RO system in a dirtier water source, like the Chesapeake Bay. Last time we made water in the Chesapeake, it had a fishy smell, but was otherwise clean.

Carbon Filters

Activated carbon is the workhorse of many water filters. It actually absorbs contaminants (aka, Absortion Filter). Our Brita filter worked like that, but it takes up important space in the galley – either on limited counter space or limited fridge space. That’s why we stopped using the Brita onour sailboat. Plus, there’s the constant getting water, but someone else didn’t refill it. Ugh.

Here’s how carbon filters work. Imagine a sponge with countless tiny holes. Activated carbon is like that on a microscopic scale. This vast internal surface area provides numerous nooks and crannies to trap unwanted chemicals like chlorine.

Two types of carbon filters:

  • Granular Activated Carbon (GAC): These filters are widely used in domestic settings. They primarily target taste and odor improvement by absorbing these impurities.
  • Carbon Block Filters: These are generally more expensive but offer superior filtration. They incorporate a denser carbon structure that not only absorbs contaminants but also physically traps particles down to a certain micron size (depending on the filter’s rating).

The Waterdrop 10UA-UF filter has both a carbon block and a polyester membrane.

Examples of Micron Sizes

Since our new water filter is 0.01 microns in pore size, I thought it’d be helpful to place that in comparison with a few common items. But first, the measurements of a micron.

  • 1 Micron = 1 Thousandth of a Millimeter (0.001mm)
  • 25.4 Micron = Visible with Magnification
  • 40 to 90 Microns = Diameter of a Human Hair

Common items and their size in microns.

Image: Relative Sizes in Microns
Image: Relative Sizes in Microns
ItemsSize in Microns
Fine Beach Sand0.3
Corn Starch0.1-0.8
Wood Smoke0.2
Coffee (finely ground)25
Normal Beach Sand30
Powdered Sugar60
Pet DanderUp to 100
Coffee (normal ground)About 200
Source: Commercial Filtration Supply

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