`Water prepping is a key element of your prepping activities.  You need to make sure that you and your dependents have enough water on hand to see you through a predicted shortage for which you are prepping for.  As well as drinking water, you need water for cooking, cleaning, hygiene and sanitation.

The Rule of Three

You will regularly see quoted the survival rule of three which says you can survive without:

  • Air – 3 minutes.
  • Shelter – 3 hours.
  • Water – 3 days.
  • Food – 3 weeks.

How Much Water?

The amount of  water needed for day-to-day survival is the subject of some debate.  The most common figure quotes is 4 litres per person per day which is 2-3 litres for drinking and 1-2 litres for other uses.  Some experts, including Cody Lundin argue that this is only acceptable if you are at rest and doing nothing.  Clearly, a more strenuous survival or SHTF situation where you will be using significantly more will mean as much as 12 litres per person per day must be allowed for.

It therefore depends on the expected situation.  If you are at home and the supply goes off for a period, you are not in a SHTF situation.  If you are on a hiking expedition in a warm or hot climate and get lost or injured, you are in survival mode.  You are then certainly going to be using more water just to do what needs to be done.

My water prepping therefore involves having as much available as is reasonable and practical.  I then calculate how long that can be made to last under different scenarios.


My Water Preps

I have multiple elements to my water prepping which cover as many eventualities as I can foresee:

Bottled Water

Bottled Water

I currently store 50 Litres of bottled water giving an immediately available source should I get no warning of a cut-off.  To keep the light out it is kept covered so it will last for years but will be rotated whenever possible.  I would like to store more but it is bulky and heavy so it not easy to find the space.

Water Available = 50L

25L Water Containers

25L Water Container

I have four 25L food-grade water containers filled with tap water. The blue containers are superior as they allow much less light in and consequently this prevents bacterial growth. Furthermore, The containers are stored in the shed, again to reduce exposure to light.  Treating the water with a few drops of bleach makes sure it is disinfected. .  They will be emptied, re-treated and re-filled every 6 months.

Water Available = 100L


Water Bob

Water Bob Water Bob


I have a water bob in storage which, assuming I have a reasonable advance notice, I can put in the bath and fill with mains water before it gets cut off. It holds up to 378 litres of water, is food grade and therefore claims to keep water fresh for up to 16 weeks.

Water Available = 378L


Conventional Hot Water System Storage

Hot Water Cylinder   Hot Water Header Tank


My central heating system includes a conventional indirect hot water system which comprises of a 140L insulated hot water cylinder in the airing cupboard fed by a 225L header tank in the loft.  I started a discussion thread on UK Preppers about using these as drinking water and there were no definite responses.  However, as far as my water prepping is concerned it is too much water to ignore.  Both the cylinder and the header tank are sealed.  There are no lead pipes so contamination risk is minimal.  As long as the heating/cooling cycle of the water doesn’t affect the water quality, I see it as a viable source.

Water Available = 365L


Water Butts

Water ButtWater Butt

I wrote about this project a while ago.  I installed guttering to my shed and summerhouse and connected it to a pair of 190L water butts.  As a result I have a combined, renewable store of rainwater amounting to 185 litres per 10mm of rainfall.  There is expansion capacity too by the linking of additional water butts or tarpaulin collectors if necessary.

Water Available = 390L


Swayer Mini

Sawyer Mini Water Filter

The Sawyer Mini is an amazing piece of kit. The manufacturer specifications state that the specification of the ‘award winning’ Mini is:

  • Rated to 0.1 micron absolute
  • Ideal for outdoor recreation, hiking, camping, scouting, domestic and international travel and emergency preparedness
  • Removes 99.99999% of all bacteria, such as salmonella, cholera, leptospirosis, and E.coli; removes 99.9999% of all protozoa, such as giardia and cryptosporidium
  • High performance filter fits in the palm of your hand, weighs 2 ounces (57g) and filters up to 100,000 gallons (30 times more than comparable filters)
  • Attached to included drinking pouch, standard disposable bottles (28 mm thread), hydration packs, or use the straw to drink directly from your water source

The Sawyer Mini is certainly small and lightweight and can filter out most hazardous water content except for the smaller viruses.  You can use it straight from the provided drinking straw, attach the squeeze bag or hook it up to a bottle or system of your own and use it as an in-line filter.  Regular back-flushing with clean water is required to keep the filter clear.

I have several of them available and they are great for your various bags (day, go, get-home, bug-out) or for general water filtering duties.


Sawyer SP191

Sawyer SP191 Water Filter

The bigger Sawyer, the SP191 is a two bucket kit supplied with everything apart form the buckets themselves.  The specification of this unit is:

  • Small, lightweight filter kit that can provide up to 170 gallons of clean water per day
  • 0.02 Micron absolute hollow fiber membrane purifier; removes 99.997% of viruses, 99.99999% of bacteria, and 99.9999% of Protozoa/Cysts
  • Housing material made from food grade ABS plastic is easily field maintainable
  • Filter output is 1-litre per minute with gravity, and with water full faucet pressure

Notice the much finer filter capability, down form the 0.1 micron of the Mini to 0.02 micron.  This increases the filtration to include almost all viruses.  The trade-off is speed which is why this is a bucket-type kit rather than an on-the-go variety like the Mini.  This is designed to set up on a permanent or semi-permanent basis and filter a supply of water using gravity (slower) or pressure (faster).


Steri Pen

Steripen UV Water Purifier

The Steri Pen is an unusual water treatment device in that it uses UV light to purify the water.  I originally bought the ‘Adventurer’ model  when I first started prepping and before I was aware of the Swayer Mini.  It is kept in my bug-out bag along with some spare CR123 batteries.  The quote from the manufacturer website states:

Lightweight water purification for peak performance in the outdoors! SteriPEN Adventurer Opti was built for the toughest mountains and rivers in the world. Backpacker Magazine gave it their Editor’s Choice Award in 2011 for changing the face of portable water purification.

To use it you apply the pen to a water bottle (e.g. a Nalgene wide-mouth bottle) and turn it on.  It will purify 0.5L of water in 48s or 1L in 90s.  The UV light kills viruses, bacteria and protozoa.  What it doesn’t do of course is to filter out any organic material in the water like a physical filter would do.  For this you would need to filter through a basic filter like a bandana or a coffee filter.

It’s not my go-to method but it’s another handy option to have available.


Oasis Purification Tablets

Oasis Water Purification Tablets

Water purification tablets are another tried and trusted method of producing drinkable water.  I use the Oasis brand and buy the 50-pack tablets which will each purify 1L of water.  According to the manufacturer website:

Oasis Water Purification Tablets are effervescent Chlorine (NaDCC) tablets which purify water to make it safe to drink. They are highly effective in killing micro organisms in water to prevent dysentery, diarrhoea, cholera and other water borne diseases.

Oasis Water Purification Tablets are effective at killing bacteria, bacterial spores, cysts, algae, fungi, protozoa and virus and are especially lethal to Entamoeba Histolytica. The causative water borne organisms on the right, amongst others, are killed by Oasis Water Purification Tablets.

I keep several boxes of tablets available and with a shelf life of around 5 years, they only need to be on a very slow rotation.




Bleach has multiple uses for health and hygiene but it can also be used to treat water for storage or drinking. Make sure that the bleach you store and use contains only Sodium hypochlorite, so no added perfumes or additives.  Unfortunately, at least her in the UK, that means that you have to settle for a weaker bleach.  All of the readily available bleaches of any strength contain perfumes.  The unperfumed varieties tend to be 1% or 1.5% concentration compared to the 4% to 6% of the perfumed bleaches.

As a rule of thumb, add 10 drops of bleach to 1L of water in a canteen or bottle.  Close the cap and let its stand for 30 minutes.  If the water doesn’t have a faint bleach smell, repeat the process.  Once it does, it is safe to drink.

Be aware that bleach, even unopened deteriorates over time so your stock should be rotated every year at the least.  Since it is so cheap, I rotate mine out every 6 months.


Water Prepping Summary

Water prepping is about having as many options available as you can.  Adding up my water storage and assuming all are full at the time, I have 1283 litres of water.  This is all either drinkable or treatable.  How many days it will last for depends on the a number of possibilities:

  • Level of physical activity
  • The rate at which the stored water will degrade
  • How quickly the renewable supply (the water butts) refill
  • What restrictions are placed on non-drinking uses such as cooking and hygiene.

If i assume the absolute basic rate of 1L of drinking water per day, my wife and I would have 641 days of water, although much of that time will require it to be boiled and/or treated.  Assuming a more pessimistic rate of use of 12L per day per person, we would have 53 days of water.  In reality, the truth is somewhere in between but at a cost of repeating myself, it is all about having options.