You’ve got a freshwater tank, a pump, PEX lines to your fixtures — the plumbing is sorted. But what about what’s actually IN the water? Depending on where you’re filling up, you could be running campground water with heavy chlorine taste, well water with sediment, or worse through your system. Filtration is one of those things I didn’t think about much at first, and then I spent way too many nights reading about it. (See our guide on How Do You Get Water in a Converted Bus? for more on this.)
The five best water filtration options for a skoolie are Berkey gravity filters (no plumbing needed, great for drinking water), under-sink carbon block filters (affordable and easy to install inline), basic inline RV filters (cheap first line of defense for your whole system), UV purification systems (kills bacteria and viruses without chemicals), and reverse osmosis systems (the most thorough filtration you can get, but bulky and wasteful). Most builders end up combining two of these — a whole-bus sediment filter on the intake plus a drinking water filter at the kitchen sink. You don’t need to go overboard, but you do need something.
For a deeper look at how the whole water system fits together — tanks, pumps, plumbing, all of it — check out our complete guide to skoolie plumbing and water systems.
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Berkey Gravity Filters
I’ll start with the one you see in every other skoolie tour video. The Berkey has become almost a cultural thing in the bus life community at this point. It’s a stainless steel gravity-fed filter that sits on your counter, you pour water in the top, gravity pulls it through the filter elements, and clean water collects in the lower chamber. No electricity, no plumbing connection, no water pressure needed. (See our guide on Skoolie Plumbing and Water Systems: The Complete Guide for more on this.)
The filtration itself is legitimately impressive. The Black Berkey elements remove bacteria, viruses, heavy metals, chlorine, pharmaceuticals, and a long list of other contaminants. We’re talking over 99.9% removal rates on most of the nasty stuff. For drinking water quality, it’s hard to beat.
“How do you keep the Berkey steady when moving down the road?”
This is the question everyone asks, and honestly it’s the biggest practical issue with using a Berkey in a bus. These things are tall, top-heavy when full, and made of metal. You hit a pothole with a full Berkey sitting on the counter and you’ve got a disaster. Water everywhere, dented stainless steel, maybe a cracked spigot.
I’ve seen people solve this a bunch of different ways. The most common is building a dedicated cubby or recessed shelf that the Berkey sits down into, so it can’t tip. Some people use bungee cords or a cabinet with a latch. One guy I saw on a forum built a plywood cradle with a cutout that matched the base diameter exactly, then mounted it to the counter with L-brackets. Others just empty the Berkey before driving and refill it when they park. That’s the simplest answer but it means you’re without filtered water while you’re moving.
The Big Berkey (2.25 gallons) is the most popular size for bus builds. It filters about 7 gallons per hour with two elements. The Travel Berkey is smaller (1.5 gallons) and works for solo travelers or couples who don’t go through much water. Budget around $300-$400 depending on size and how many filter elements you get. Replacement filters run about $100-$120 for a pair, and they last for roughly 6,000 gallons — which in a skoolie is usually a couple years.
The thing I like about the Berkey is the simplicity. Nothing to install. Nothing to wire. Nothing that depends on your plumbing system working. If your pump dies, if a line bursts, you’ve still got clean drinking water. That independence is worth something when you’re living on the road. (See our guide on How Do You Do Laundry Living in a Bus? for more on this.)
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Under-Sink Carbon Block Filters
So the Berkey handles drinking water, but what about the rest of your system? This is where under-sink carbon block filters come in, and honestly for a lot of skoolie builds this is the sweet spot between cost, performance, and hassle.
A carbon block filter is a sealed cartridge that your water line runs through. You mount it under the sink, splice it into the cold water line going to your faucet, and that’s it. Water passes through a dense block of activated carbon that grabs chlorine, sediment, volatile organic compounds, and a bunch of chemical contaminants. Most good ones filter down to 0.5-1 microns.
The brands you see most often in bus builds are Doulton, Woder, and Multipure. Price range is $50-$150 for the housing and first filter, then $30-$60 per replacement cartridge every 6-12 months depending on your water usage and how dirty the source water is.
“How do they connect to a water source?”
With an under-sink setup, the filter connects directly to your existing cold water PEX line. You cut the line, add a couple of push-fit connectors (SharkBite or similar), and the filter sits in between. Some people install a separate small faucet on the sink just for filtered drinking water, so the filter only works when you’re getting water to drink or cook with. That extends the filter life significantly because you’re not running all your dish water through it too.
What I found is that most builders who go this route end up with a two-stage setup. The first stage is a sediment pre-filter (catches the big stuff, dirt, rust, sand), and the second stage is the carbon block for the chemical filtration. You can get combo housings that hold both cartridges for $60-$100. The sediment filter protects the carbon filter from clogging too fast, and together they handle basically everything except bacteria and viruses.
One thing worth mentioning — carbon block filters are flow-rate sensitive. The slower the water passes through, the more contact time it has with the carbon, and the better the filtration. Most are rated at 0.5-1.0 GPM. Your RV pump pushes more than that, so the filter is doing some restricting. I’ve heard from a couple people that the flow rate at the faucet feels noticeably slower with one of these installed. Not unusable, just slower. Something to know going in.
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Inline RV Water Filters
Alright, now we’re at the cheap and simple end of things. Inline RV water filters are those blue or white canisters you see screwed onto the end of a water hose at campgrounds. You’ve probably seen them a hundred times. Camco, Culligan, and a few others make them and they cost $15-$30.
These aren’t doing the heavy lifting that a Berkey or carbon block system does. An inline RV filter is basically a granular activated carbon cartridge in a plastic housing. It reduces chlorine taste and odor, catches some sediment, and that’s about it. It’s not removing bacteria. It’s not removing heavy metals in any meaningful way. It’s a basic taste-and-smell improvement filter.
“OK now where do you get all of this water from to take a bath, wash your dishes, and to drink???”
This is actually a great question to address here because it gets at why a lot of people use inline filters in the first place. When you’re filling your tank from different sources — a campground spigot in Arizona, a friend’s garden hose in Oregon, a fill station at a truck stop in Texas — the water quality varies wildly. Some of it tastes fine. Some of it tastes like a swimming pool. Some of it has visible sediment.
We covered where you actually get water in another article, but the short version is you’re filling from campground hookups, RV fill stations, and outdoor spigots wherever you can find them. The inline filter is your first defense against whatever’s in that water going into your tank.
A lot of builders use these as a pre-filter on the fill hose. You screw it onto the end of your drinking water hose before the water even enters the bus. That way the big stuff — sediment, chlorine, whatever gunk is in the campground pipes — gets caught before it hits your tank. Your tank stays cleaner, your pump filter stays cleaner, and if you’ve got a better filter system inside the bus, it lasts longer because it’s not doing double duty.
Replace these every 3-4 months or whenever the flow rate drops noticeably. They clog. It’s what they’re supposed to do. At $15-$30 a pop, they’re disposable. Some people carry two or three spares and swap them out as needed. I’d call this a must-have even if you’ve got better filtration inside the bus. It’s cheap insurance.
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UV Purification Systems
So here’s where things get a little more serious. Everything we’ve talked about so far handles chemicals, taste, odor, sediment — the stuff that makes water unpleasant. But what about the stuff that makes you sick? Bacteria, viruses, protozoa, the biological contaminants that a carbon filter won’t reliably kill?
That’s the UV purification question.
A UV system works by running water past an ultraviolet light that damages the DNA of microorganisms so they can’t reproduce. It doesn’t remove anything from the water — the bacteria are still technically in there, they’re just dead. But dead bacteria don’t make you sick, so the end result is the same.
I remember reading about a couple who were filling their tank from a creek in Colorado using a pre-filter to catch sediment and then relying on UV to kill everything biological. They’d been doing it for over a year with no issues. That’s an extreme case and I wouldn’t recommend it as your primary water strategy, but it shows what UV can do when you combine it with basic physical filtration.
The two brands I kept seeing in skoolie builds were Sterilight and VIQUA (which are actually the same parent company now). A point-of-use UV system runs $150-$400 depending on flow rate and features. The bulbs last about 9,000 hours, which for most skoolie use means replacing once a year. Replacement bulbs are $50-$80.
Here’s the catch — UV systems need electricity. Not a lot, most draw 14-40 watts, but they need it constantly while water is flowing. If you’re on solar and trying to conserve power, that’s another draw on your system. They also need clear water to work properly. If the water is cloudy or has particulates, the UV light can’t penetrate evenly and some organisms survive. So you basically need a sediment pre-filter before the UV stage anyway.
For most skoolie builders who are filling from municipal water sources — campgrounds, city water hookups, fill stations — the water has already been treated and UV is honestly overkill. Where it makes sense is if you’re boondocking a lot and filling from untreated sources, or if you just want the peace of mind that comes from knowing literally nothing alive is getting through your system.
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Reverse Osmosis Systems
“Is it possible to put a shower on recycled water looping through a purifier?”
I want to address this question before getting into the RO details because it keeps coming up and it connects to why some people consider reverse osmosis in the first place. The idea is: filter your gray water, loop it back, use less fresh water overall. And reverse osmosis is the only filtration method that can theoretically get gray water clean enough to reuse.
But practically? In a bus? It’s a tough sell. RO systems waste a lot of water — for every gallon of clean water they produce, they dump 2-4 gallons of reject water. That ratio kills you when you’re trying to conserve. The membranes are expensive, the system takes up space, and the flow rate is slow. We talked about this a bit in our plumbing guide — the recirculating shower idea sounds brilliant but the complexity and cost usually aren’t worth it versus just taking shorter showers.
Now, for straight drinking water filtration, RO is the gold standard. A reverse osmosis membrane has pores so small that basically only water molecules pass through. We’re talking 0.0001 microns. It removes dissolved solids, heavy metals, fluoride, nitrates, arsenic, lead, sodium, practically everything. The water that comes out is about as pure as water gets.
Countertop RO units have gotten way more compact in the last few years, which is what’s made them viable for bus builds. The AquaTru and SimPure are two I kept seeing recommended in forums. They don’t need to connect to your plumbing — you pour water in the top, it runs through the membrane, clean water collects in a reservoir. Kind of like a Berkey but with RO-level filtration. They cost $300-$500 and the filters need replacing every 6-12 months at about $60-$80 per set. (See our guide on What Kind of Toilet Should You Use in a Skoolie? for more on this.)
The traditional under-sink RO systems work in a bus too but they’re more involved. You need space for the membrane housing, a storage tank (usually 2-3 gallons), and somewhere for the waste water to go. The waste water line typically drains into the gray water tank, which means you’re partially filling your gray tank just by making drinking water. On a bus where every gallon matters, that’s a real consideration.
I think RO makes the most sense for people with specific water quality concerns. If you’ve got a family member with a compromised immune system, or you’re filling from sources where you genuinely don’t know what’s in the water, the thoroughness of RO is worth the tradeoffs. For the average skoolie build, it’s more system than most people need.
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Related: Can You Put a Washer and Dryer in a School Bus?
So what should you actually get?
After going through all of this, here’s where I landed. Most skoolie owners don’t need the fanciest setup. They need two things: a basic inline filter on the hose to protect the tank, and a decent filter at the kitchen sink for drinking water. That combination handles 90% of what you’ll encounter on the road, and it costs under $200 total.
If you want to go one step further, a two-stage under-sink system with a sediment pre-filter and carbon block gives you really solid everyday filtration. Add a Berkey on the counter if you want a backup that works even when your plumbing doesn’t.
UV and RO are specialty tools. They’re there for specific situations — boondocking with untreated water sources, or needing the absolute cleanest water possible for health reasons. Most people filling from campgrounds and city water hookups won’t ever need them.
The one thing I’d say is don’t skip filtration entirely. Even treated municipal water varies a lot from place to place, and you’re filling from dozens of different sources over the course of a year. A $20 inline filter on your hose is the bare minimum. Everything beyond that is about how much peace of mind you want and what your budget allows. Start simple, see what your water tastes like, and add more filtration if you need it. That’s basically what everyone I’ve talked to ended up doing anyway.
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