Water · Guide

How to Filter Water at Home with a Gravity Filter (the Boroux Legacy)

How to set up, use, and maintain a stainless gravity water filter for daily drinking water and long emergencies: priming, what the Boroux Legacy removes and what it does not, care, sizing, the Berkey comparison, and where it fits with storing and treating water.

Quick facts

Capacity3 gallons (Compact: 1.8)
FlowAbout 1 gallon an hour with 2 filters, 2 with 4
Filter life12 months per pair; scrub every 3 to 6 months
Removes
- Lead and heavy metals
- PFAS
- pesticides
- VOCs
- pharmaceuticals
- microplastics
- chlorine taste
Does not removeBacteria, viruses, cysts: disinfect surface water first
BuildSeamless 304 stainless, stainless spigot with ceramic valve, lifetime chamber warranty, 60 day trial

A gravity filter is the one piece of water gear that works the same on an ordinary Tuesday and on the day the pumps stop: pour in the top, draw from the spigot, no power, no plumbing, no pressure. The Boroux Legacy is the one I use every day and the one I count on for a long emergency. This page is how to set it up, what it removes and what it does not, how to keep it running for years, and how it fits with storing and treating water.

See the Boroux Legacy60-day satisfaction guarantee, lifetime warranty on the stainless chambers

Six numbers to know

3 galin the systemUpper chamber to fill, lower chamber to draw from. The Compact holds 1.8 gallons.

1 gal / hrwith two filtersTwo gallons an hour with four. Fill it before bed and it is done by morning.

4 peopleon one fill a dayTwo filters serve up to four people filled once daily; four filters serve up to eight.

12 monthsper pair of filtersReplace the pair yearly. Write the date on the filter stem when you install it.

0.5 to 1 µmparticles, 98.9% reducedMicroplastics, sediment, and the fine grit that clouds surface water.

0 wattsof electricity, everGravity does the work. It runs in a blackout, at a cabin, or on a counter with no plumbing.

How a gravity filter works

1FillPour water into the upper chamber. Tap, well, stored, or pre-treated surface water.
2FilterGravity pulls it down through the densely packed carbon of the Foundation filters. Silver in the block keeps the filter itself from growing anything.
3CollectChemicals, metals, and particles stay behind. Clean water drips into the lower chamber.
4PourDraw from the stainless spigot. A ceramic valve, so it does not weep or wear like plastic.

Set it up the first time

Most complaints about gravity filters, cloudy water, slow flow, a filter that fails early, come down to one thing: the filters were not primed. Priming forces water through the dry carbon block so it flows evenly from the first fill. Do it properly once and the system is boring for a year.

Wash and prime

Wash both chambers, the lid, and the spigot with warm soapy water and rinse.The stainless comes with machining oil on it. Half water, half vinegar takes off any film.
Prime each Foundation filter.With the automatic primer it is about 90 seconds a filter. With the blue silicone tool on a faucet, run water through each filter for at least 10 minutes until it beads evenly over the whole surface.
Fit the filters through the upper chamber and tighten the wingnuts below.The Stem Saver ring takes the strain so the stem does not snap if the chamber is knocked. Plug the unused holes if you run two filters.

First fill

Seat the upper chamber, fill it to the top, and let it run through.The first batch may carry a little carbon dust; pour it on the garden.
Check the flow.A primed pair moves about a gallon an hour. Much slower, or water that stays cloudy, means a filter did not prime; pull it and prime it again.
Keep the lower chamber emptier than the upper is full.Overfilling the lower chamber floods the filter stems. Draw a jug before each refill.

Every day

Fill it in the evening, draw from it all day.Three gallons a day is a family's drinking and cooking water. Coffee, tea, and cooking rice all taste better for it.
Keep the lid on.The chambers are vented so they never airlock, and the lid keeps dust and light out of the lower chamber.

What it removes, and what it does not

The Foundation filters were tested at an ISO 17025 lab (IAPMO R&T) across more than 80 contaminants, to the full rated life rather than extrapolated from a small sample. The maker's own numbers:

Group	What was tested	Reduction
Heavy metals	Cadmium, chromium, lead, mercury, uranium, cesium	Up to 99.36%
Forever chemicals and plastics	PFOA, PFOS, and five other PFAS compounds, BPA, chlorine, chloroform	Up to 99.5%
Pharmaceuticals	Atenolol, carbamazepine, estrone, ibuprofen, naproxen, phenytoin, trimethoprim and more	Up to 99.5%
Pesticides and herbicides	24 tested, including atrazine, glyphosate, DEET, lindane	Up to 99.95%
Volatile organic compounds	Benzene, toluene, xylenes, TCE, and 30 more	Up to 99.97%
Disinfection byproducts	Trihalomethanes, chloroform, bromoform, haloacetonitriles	Up to 99.68%
Microplastics and particles	0.5 to 1 micron	98.9% on average (NSF/ANSI 42 Class I, 401)
Fluoride	Needs the separate Proactive fluoride filter, 1,000 gallons per pair, not sold in CA or IA	Up to 99%
Taste and odor	Chlorine, sulfur, the plastic taste of stored water	Removed

What it does not do: kill germs

Boroux states plainly that the Foundation filter is not intended to filter microorganisms; the silver in it protects the filter, not you. So treat it as a chemical and particle filter, which is the hard part of the job that boiling and bleach cannot do, and give it water that is already free of bacteria, viruses, and cysts. Tap and well water that tests clean go straight in. Creek, pond, rain barrel, or flood water gets disinfected first, then filtered for taste and chemicals.

BoilA rolling boil for 1 minute, 3 minutes above 5,000 feet, kills everything. Let it cool, then run it through the Boroux for the chemicals boiling cannot touch.Water: storage and purification

Pool shockCalcium hypochlorite stock at 1 tablespoon per gallon, 30 minutes, then through the filter, which also strips the chlorine taste. Dry granules keep up to 10 years.Purify water with calcium hypochlorite

IodineLugol's 2% at 5 drops per quart, 10 if cold or cloudy, 30 to 60 minutes. Light enough for a pack. Not for more than a few weeks of use.Purify water with Lugol's iodine

Pre-filter the mudCloth, then a gravel, sand, and charcoal bottle filter if the water is brown. Clear water disinfects faster and the carbon block lasts longer.DIY soda bottle water filter

Boroux vs Berkey

Families, preppers, and off-grid homes trusted Berkey for decades. In December 2022 Berkey had to stop selling its most popular filters. Not a safety failure, but it left a lot of people with a stainless housing and no replacements. The team behind Boroux took what worked and redesigned the weak points. I still own two Berkeys and like them; the details are where the Boroux wins.

Feature	Boroux Legacy	Royal Berkey
Filter protection	Stem Saver ring takes the load off the filter stem	No protective support
Spigot	Stainless steel with a ceramic valve	Basic plastic
Chambers	Seamless one-piece 304 stainless	Welded or multi-piece
Airflow	Vented chambers, no airlocks	No venting, more prone to flow problems
Warranty	Lifetime on the steel chambers	No lifetime warranty
Testing	ISO 17025 lab, tested to the full claimed life	Older testing, extrapolated from 500 ml samples
Trial	60 days	No comparable trial
Your old Berkey	Foundation and Proactive filters fit a Berkey housing	Keeps working with Boroux filters in it

Care: Keep it running for years

Every 3 to 6 months: scrub the filtersPull the filters, scrub the outside under warm running water with an abrasive sponge (no soap), re-prime, and refit. Flow comes right back. The surface loads up with what it caught.

Every 12 months: new filtersReplace the pair on the date written on the stem, sooner if flow will not recover after a scrub. Keep the next pair on the shelf now; the filter you cannot get is the one that matters.Spare parts: water treatment and storage

Chambers and spigotHalf water, half vinegar, then rinse. Check the spigot washer and the wingnuts when you scrub the filters. The red dye test is being retired; go by flow and by the calendar.

Storing it unusedGoing away for weeks? Empty it, pull the filters, let everything dry, and store the filters in a sealed bag. Prime again before the next use. Never store it wet and closed.

The spares I keep: a second pair of Foundation filters, a spare spigot, hole plugs and wingnuts, and the priming tool. On the Proactive fluoride filters, count 1,000 gallons, which is 6 to 12 months for a household, and prime those too.

Sizing for your household

Legacy, two filters

Holds: 3 gallons
Flow: About 1 gallon an hour
Serves: Up to 4 people on one fill a day
Filters a year: One pair
Footprint: 23 inches tall assembled, 9 inch diameter; 15 inches nested for storage

Legacy, four filters

Holds: 3 gallons
Flow: About 2 gallons an hour
Serves: Up to 8 people, or heavy cooking and canning use
Filters a year: Two pairs, or one pair replaced twice as often
Footprint: Same housing; the extra filters go in the two plugged holes

The Compact is the same filter in a 1.8 gallon housing for one or two people or a small counter. I keep two full systems at home and more at my cafe, because one is none and two is one; the second one is also the one that goes in the truck.

Where it fits in the water plan

Store it

One gallon per person per day, two weeks minimum

Sealed bottled water keeps about two years; food-grade jugs of tap water get rotated every 6 to 12 months. Stored water goes through the Boroux before drinking and tastes like it came from the tap that morning.

Water: storage and purification

Source it

A creek, a pond, a spring, the rain off the roof

Water weighs about eight and a half pounds a gallon. A frame pack and two 3 gallon AquaBricks move six gallons a trip; that is the daily fill for the Legacy and then some.

How to source, carry, and filter local fresh water

Treat it

Boil, pool shock, bleach, or iodine kills what lives in it

Pool shock is the one to store: a pound of dry calcium hypochlorite treats thousands of gallons and, sealed cool and dry, stays usable for many years, losing a few percent of its strength a year. Never near acids or ammonia.

Purify water with calcium hypochlorite Never-mix chart

Filter it

The Boroux takes out the chemicals, metals, and the treatment taste

The last step, and the one that makes treated water something the family will actually drink for weeks. It is also the everyday step: the same unit filters the tap water now.

The Boroux Legacy Spare parts: water treatment

What goes wrong

Skipping the primeCloudy water and a trickle, then a filter blamed for a job it was never set up to do.

Pond water straight inThe carbon block is not a germ filter. Disinfect first, filter second.

No spare filtersThe pair lasts a year on the shelf; the pair you cannot buy during a shortage lasts forever.

Hot waterNever pour hot water into the upper chamber. It damages the carbon block and the seals.

Overfilling the bottomFilter stems sitting in filtered water stop flowing and can push water back up.

Letting it sit dry and closedDry it open, or keep it in daily use. Damp and closed grows what you bought it to avoid.

Order the Boroux Legacy3 gallons, no power, one pair of filters a year

Questions this answers

Tap a question for the short answer.

What is the best gravity water filter for preparedness

My pick is the Boroux Legacy: seamless 304 stainless, 3 gallons, no power or plumbing, about a gallon an hour through a pair of Foundation filters that last 12 months, a lifetime warranty on the chambers, and a 60 day trial. I use it daily and keep a second one as a backup.

How do I prime boroux filters

Run water through each dry filter until it beads evenly over the whole surface: about 90 seconds with the automatic primer, or at least 10 minutes with the blue silicone tool on a faucet. An unprimed filter gives cloudy water, a slow trickle, and a shorter life. Re-prime after every scrub.

Does a boroux filter remove bacteria and viruses

No. Boroux states the Foundation filter is not intended to filter microorganisms. It removes metals, PFAS, pesticides, VOCs, pharmaceuticals, microplastics, and chlorine taste. Give it tap or well water that tests clean, or disinfect surface water first by boiling, calcium hypochlorite, or iodine, then filter.

How long do boroux filters last

Replace a pair of Foundation filters every 12 months, and scrub them under warm water with an abrasive sponge every 3 to 6 months to restore flow. The separate Proactive fluoride filters are rated for 1,000 gallons, about 6 to 12 months.

Is boroux better than berkey

I own both and rank the Boroux higher: a Stem Saver ring that stops filter breakage, a stainless spigot with a ceramic valve instead of plastic, seamless one-piece chambers, vents that prevent airlocks, ISO 17025 lab testing to the full rated life, a lifetime chamber warranty, and a 60 day trial. Boroux filters also fit a Berkey housing.

Does a gravity water filter need electricity

No. You pour water into the upper chamber and gravity moves it through the filters into the lower chamber, so it works in a blackout, at a cabin, or on any counter with no plumbing.

How much water does the boroux legacy hold

3 gallons, enough for about four people's drinking and cooking water on one fill a day with two filters, or eight people with four. The Compact model holds 1.8 gallons.

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