Water filter emergency kit: what actually works?

Reading time: ~10 minutes

How much water should be in an emergency kit?

Start with the quantity, not the gadget. The government advises being self-sufficient for three days, and according to Brabant Water you should allow at least 3 litres of water per person per day: 2 litres for drinking and 1 litre for preparing food. For a family of four that comes to at least 36 litres.

That 3 litres per person per day is a minimum for drinking and cooking. Water for washing your hands, doing the dishes or flushing the toilet isn't included. Allow for that separately, and also think of pets: Brabant Water cites about half a litre per animal per day.

Good news about the odds you'll actually need that supply: during a power outage the tap usually keeps running as normal. According to Brabant Water, water companies can keep supplying water on their own power source for ten days. The exception is high-rise buildings: if you live above the third floor, there's often an electric pump involved, and that does stop without power.

If an outage lasts longer than 24 hours, your water company provides emergency drinking water via a tap point nearby, also at 3 litres per person per day. You bring your own bottles or a jerry can. What to do in the first hours of such an outage is set out step by step in our article on no tap water and what to do about it.

Which water filters are there for an emergency kit?

Search for "water filter emergency kit" and you'll mainly see cheap filter straws. On Dutch webshops, those portable emergency filters are priced at roughly €9 to €50 at the time of writing, and the capacity sellers cite ranges from 1,000 to 5,000 litres. That difference in price says little; the difference in type says everything. There are five categories, and each solves a different problem.

1. Filter straw or filter bottle

You suck the water yourself through a hollow-fibre membrane. Compact, light and cheap, which is why it's popular in a backpack. Downside: you can barely stock up water or cook with it, because you drink one sip at a time. Fine for one person on the move, awkward for a family at home.

2. Gravity bag filter

You hang up a bag or bucket and let the water drop through the filter. This type does deliver litres in a row, without power and without pumping, making it the most practical for a household. We explain how this technology works in our guide on gravity water filters.

3. Pump filter

You push water through the filter with a hand pump. Fast and independent of height difference, but mechanical, so something can break, and it takes physical effort per litre.

4. Purification tablets and boiling

Not a filter, but disinfection. Tablets based on chlorine or iodine kill pathogens, but don't remove sand, chemicals or heavy metals, and leave a chlorine taste. Boiling does the same: the RIVM states that after three minutes of boiling all pathogens are out of the water. Without gas or power, however, you can't boil water, and that's exactly the scenario you're building an emergency kit for.

5. Fixed household filter under the sink

An inline filter that sits permanently on your cold water pipe, such as the PureFilter Mineral+. This isn't an emergency filter: it works on the pressure in the pipe and stops if no water comes out of the tap. Its job is the other 362 days of the year. If you want to see the types side by side, our page on which types of water filters there are and what they do gives the full overview.

What an emergency filter does and doesn't remove from water

This is where most product pages cut corners. A cheap emergency filter with a hollow-fibre membrane holds back bacteria and parasites, because they're larger than the pores. Viruses are smaller and slip past many filters; only filters with a very fine membrane, a chemical step or UV address those. Sellers aren't always clear about that.

That distinction is relevant in the Netherlands, because the bacteria involved in contamination are well known. The RIVM explains that water companies test for E. coli and enterococci, because they indicate faecal matter in the water. If they're found, boil-water advice follows. More on those two indicators is in our piece on enterococci and E. coli in tap water.

If you want to know how much good multi-stage filtration can actually achieve, the comparison with a filter jug is instructive: that mainly removes chlorine and taste and little else. We've worked that out in our review of Brita filters.

Storing tap water yourself: the cheapest supply

The bit that almost every emergency-kit page skips, even though it gives you the most benefit. Dutch tap water is high quality and you can simply store it yourself, which is a lot cheaper than buying 36 litres of bottled water. Brabant Water provides a clear method for this.

• Packaging: use clean, well-sealing bottles or jerry cans.
• Hygiene: wash your hands before filling and rinse the bottles first with clean tap water.
• Filling: fill to the brim so as little air as possible is next to the water, and seal immediately.
• Storing: put the bottles in a cool, dark place, for example a cellar or pantry.
• Refreshing: write the date on the bottle and replace the water every six months.

Put two fixed moments a year in your calendar, for example when the clocks change, and then you don't need to think about it further. Storing tap water is also, incidentally, why taste matters: water you actually like, you drink when refreshing it instead of pouring it down the sink.

And your fixed water filter at home, does it help?

Honest answer: not during the outage itself. An under-sink filter such as the PureFilter Mineral+ sits on your cold water pipe and works on the pressure in that pipe. If no water comes out of the tap, no water comes through the filter either. Anyone who tells you a household filter replaces your emergency kit is selling you something.

Where it does count is the water you put into your supply and the water you drink for the rest of the year. The Mineral+ filters more than 100 contaminants, including PFAS, microplastics, heavy metals and pharmaceutical residues, by around 99%, and is certified to NSF 42, 53, 61 and 372. It then adds calcium, magnesium and potassium back in via Swedish Mineral Rock™, giving the water a softer, fuller taste. One filter lasts 15,000 to 20,000 litres, roughly twelve months for one to three people.

One more practical point for anyone with a boiling water tap: it doesn't filter your water and needs power, so it stops working during a power outage. How to combine a filter with that is on our page about a water filter with a Quooker.

In short, two different functions. A small bag filter in the utility cupboard covers the unlikely scenario, and a fixed water filter for the kitchen covers daily water quality. They don't compete with each other.

When the tap works again: boil-water advice and flushing

This part is also missing from almost every emergency-kit page, even though you'll need it far more often than the filter itself. After repair works or a pipe burst, faecal matter can enter the drinking water. The RIVM describes what happens then: the water company issues boil-water advice, and you boil the water you want to drink for three minutes first. After that, all pathogens are gone. Showering, brushing your teeth and washing up with unboiled water isn't dangerous according to the RIVM, and the advice remains in place until checks show the water is clean again.

If you collect emergency drinking water from a tap point, according to Brabant Water that's just as safe as normal drinking water, but your own jerry can might not be. So boil it for three minutes to be safe and let it cool. If you can't boil it, use the cleanest possible bottles and preferably drink the water within 24 hours.

Three things to do as soon as supply resumes:

• Flushing: run the cold tap for a few minutes until the water is clear and no longer looks aerated or brown.
• Wait before filtering: if there's a fixed filter on your pipe, run the tap first before drawing filtered water, so dirt and air from the pipe don't end up in your filter.
• Topping up your supply: refill your bottles with fresh tap water and write a new date on them, so your kit is complete again.

If brown water comes out of the tap or the pressure stays low, report that to your water company. What discolouration usually means is explained in our article on filtering iron out of tap water.

Buying advice: what do you buy when?

Put your budget in the right order, and you won't need to buy much.

• First the supply. Three jerry cans or a set of bottles plus a six-monthly reminder. This covers the situation you could realistically experience in the Netherlands and costs almost nothing.
• Then a gravity bag filter. For a household, this type works better than a straw, because you filter litres in a row without power.
• Purification tablets as a backup. Light, keeps for years and handy if you can't boil water.
• Then daily water quality. This is where the benefit lies for the rest of the year, and for that you look at a fixed filter rather than an emergency filter.

At PureFilter, we find that customers mainly choose the daily route: not out of fear of disasters, but because they want better water from their own tap every day. If you're torn between types of household filters, our comparison of the best water filter lines them up, and if you'd rather go portable on holiday, our overview of a water filter for travel helps.

Frequently asked questions

Conclusion

A water filter in your emergency kit is useful, but it isn't the most important part. That's the supply: at least 3 litres per person per day for three days, so 36 litres for a family of four, stored in clean, sealable bottles and refreshed every six months. After that comes a gravity bag filter, and purification tablets as a backup for the viruses a membrane can let through.

What a portable emergency filter doesn't do is improve your daily tap water, and for most Dutch households that's where the real benefit lies. Dutch tap water is good, but the last stretch of pipe in your own home falls outside your water company's control, and PFAS, microplastics and pharmaceutical residues call for finer filtration than an emergency filter can deliver. For that, an under-sink filter that purifies and mineralises is the logical choice, for less than one cent per litre. Prepare for the three days that go wrong, and improve the 362 days that everything works.