How to Make a Water Filter in a Barrel

Rain is like manna from heaven. All life here on our lovely planet requires water to live, and lots of it. Just like planet earth, our bodies are mostly water, so ya gotta have it.

Most people are tapped into their city water and they are comfortable with that. But the best water is deep in the ground, not to mention what will they do if something were to happen to that water supply…

I remember being a kid at my grandparent’s place, or their friends and family’s farms, and there was always a hand pump behind the house.

The water that came out of there was so cold and refreshing. On a hot summer day, after fishing or just running around in the woods, I went straight for that over pops or iced tea.

I also remember my grandparents and my uncle having rain barrels on the corners of their houses or sheds. They used that water on their gardens, because being rainwater it was clean and free of the chemicals and impurities that you get in your tap water (They keep the tap water within the legal limits though, mmmm, refreshing, huh?).

Is It Legal?

Can you believe that in some states there are laws that regulate how to catch and save rainwater on your own property? For instance, in Colorado you are allowed only two rain barrels for collecting rainwater.

In Nevada it is currently only legal to collect rainwater if it is being used for wildlife. In Oregon there is such strict regulation on rainwater collection if you live there and plan to build a rainwater collection system it is advisable that you research the laws as you could find yourself in hot water (I just had to do it, sorry).

Just like in Oregon, Utah strongly restricts rainwater collection and so you should research the laws there as well if you plan to construct a rainwater collection system.

The rest of the states throughout the United States loosely regulate rainwater collection, have no regulation, or strongly suggest that you do collect rainwater.

In the U.S. Virgin Islands there has been regulation since 1964 requiring new construction to have a self-sustained potable water system, like wells or cisterns, for collecting rainwater.

Getting Started

I have lived in a couple of houses that had large underground water cisterns that were directly fed from the gutter systems on the house. We didn’t use them, but I liked knowing they were there if I needed them.

If you don’t have these large cisterns for storing water, your next best choice is to use the plastic stock water tanks, or you can just use plastic food-grade barrels. You know, the blue plastic barrels.

Those are perfect for making your rainwater collection system as they previously contained food items so you know they are safe to drink from, and being plastic they are easy to drill and cut for your plumbing lines.

Here is a video similar to what I described:

DIY Backyard Rainwater Harvesting Using Repurposed Food Grade Barrels

My cistern tanks were 1000 gallons. To get that amount of water using barrels you’d need 20, 50-gallon barrels. That’s a lot of barrels so if you’re only concerned with a smaller amount of water reserves.

For the sake of this article, let’s say that you line 9 barrels up across the back of your house or barn. I like an odd number so there is a center barrel. Make sure they all have the original lids for them so that you can clamp them on tight.

Setting Up

Usually, the gutter on your house has a high point in the center and slopes to each end of the building; we will use that as an example. You can use concrete blocks or you can make a steel rack that the barrels sit on.

You can build it out of logs if you have to, whatever it takes. The goal is to have the barrels on each end set at the same height and to have them a couple of feet or so off the ground.

The downspout from the gutter will go into a filter box over the barrel at each end. This filter is just a sheet metal box with a screen in it to catch leaves and bugs etc. and then a downspout that goes into the barrel.

You can easily access it to regularly clean it of debris by having a flap door on top of it next to the downspout pipe.

So, each barrel on the end is a couple of feet off the ground and has a filter box on it. You want the next barrel in line from each direction to be about four to six inches lower, then the next one four to six inches lower, etc. until you get to the center barrel.

If the end barrels are two feet off the ground the center barrel will end up being only six to eight inches off the ground.

You can make the end barrels a little higher if you want to make sure you have the clearance, but being two feet off the ground is usually low enough to be able to reach the filters without a ladder and is still high enough to get them all in that descending order.

This setup gives you 9 barrels arranged in a sort of a “V” pattern. Each barrel has a spillover pipe coming from the side at the top that goes into the top of the next barrel.

This spillover pipe should extend about halfway down inside the inlet barrel (the higher barrel). This prevents any floating debris that made it through the screen from getting into the next barrel. I would use a 2” PVC pipe for the spillover pipes.

You can do the same thing with only seven, five, or three barrels if you want. You can go the other way and put more barrels if you want, but try to keep it an odd number so each side array feeds into the last barrel which will be in the center.

When you get to the center barrel it will contain the filtering material and a spout.

The Final Barrel

The final barrel that the water comes to in the system, the center barrel, will be the filter barrel. Rainwater it is already pretty pure and clean, but the system isn’t 100% sealed.

Filtering it makes sure there aren’t any surprises in it. You want to line the bottom of the barrel with clean gravel. For best results, you’ll want to use a few different sizes.

Start at the bottom with gravel in the 3/4” range, put it about 8 or 10 inches deep. Then go over that with a layer about 4 inches deep of about 1/2” diameter size, then over that with a layer 4 inches deep of 1/4” or so diameter gravel over the gravel you want to put activated charcoal.

barrel filter diagram

You can use regular charcoal, but activated charcoal is much more porous, and does a much better job in filtering impurities from water. The more charcoal you put the better it filters. I’d go about 10” deep.

Finally, over the charcoal layer, you will put a layer of sand about 6 inches deep, and pack it in. You can put a layer of thin cloth between each of the three layers of sand, charcoal, and gravel to keep the layers separated.

Cheesecloth, or a thin t-shirt or similar, will suffice. You should take the filter apart and clean it, and put new charcoal and sand every so often.

A sand filter for a swimming pool can go for as long as 5 or 6 years before it has to be changed. Since you’re drinking this water, I’d change the charcoal and sand two or three times a year and clean the barrel.

The way this filter system works is the sand stops all the larger particulate matter, while the charcoal traps microscopic particulate matter and chemical impurities that the sand can’t get.

Then finally, the gravel at the bottom creates a pocket, or reservoir, for clean water to sit and keeps the spout clear of obstructions. You want the spout to exit the barrel at the bottom where the gravel is.

Final Treatments

The water in these barrels is technically clean. Especially after it comes out of the last barrel, which is the filter barrel.

But, in order to make sure it is completely safe and 100% potable water, I would still do a final treatment using one of the following methods before I drank it.


The easiest way of treating water and making it potable is by simply boiling it. You can boil mud puddle water and make it potable because boiling kills any, and all, bad nasties that may be lurking in the murk.

When you boil water to make it safe to drink, make sure to bring it to a full boil for 1 full minute or more. Keep in mind; once it starts boiling, it is evaporating. If you boil it too long, you will actually lose a little to the air. After you boil it, let it cool.

If you have a couple of water-holding vessels, just pour them back and forth, and that will help the taste a little by aeration, and rid the water of:

  • Volatile organic materials such as benzene (gasoline impurities)
  • Ammonia
  • Methane
  • Chlorine
  • Hydrogen sulfide
  • Dissolved metals such as iron and manganese
  • Many oils
  • Algae by-products

Using Bleach

Another way of treating water, to make sure it is safe and potable, is to treat it with chemicals.

Bleach is the best thing to kill off the bad nasties that might be in there. It doesn’t take much.

  • If you have some cleaning bleach that says it is 5% chlorine you just need two drops of chlorine per quart (or liter) and 8 drops of chlorine for 1 gallon.
  • If it has lower than 5% concentrate chlorine, then you need to add 7 to 10 drops per 1 quart or liter, and 40 drops for 1 gallon.

Let stand for about half an hour and taste it. There should be a slight chlorine taste. If not, then you need to repeat the treatment and let it sit for another quarter of an hour.

If then the chlorine taste is strong, let it stand for a couple of hours (or so). Then pour it back and forth between two vessels to aerate it (as discussed above).

Rainwater Filter Variation With Buckets

You can build this same system on a smaller scale using 5-gallon buckets.

If you use 5-gallon buckets, you can do a stacked system by attaching the lid for the lower bucket to the bottom of the upper bucket when you screw the filter pipe on. This makes the buckets attached together. You need four buckets.

With buckets, you arrange the filter materials a little differently:

  • The upper bucket will have the coarse gravel.
  • The middle bucket will have the sand.
  • The third bucket will have the charcoal.
  • The bottom bucket will be a clean water reservoir with a spigot coming out of the side about 1-2” off the bottom of the bucket.

You just take a piece of 1 1/2″ – 2” PVC pipe about 4” long and glue a male threaded fitting on it. You insert that through a hole in the center of a lid and the bottom of a bucket.

You need three like this. Put 8-10” layer of gravel in the top bucket, snap that onto a middle bucket with 8-10” of sand in it, and snap that onto the third bucket that has the activated charcoal in it.

The three filtering buckets sit on the fourth, so it makes a fairly tall stack. If you set the whole stack on a stand (a couple of cinder blocks will suffice, whatever it takes), this allows you easier access to the spigot. This system will filter enough potable water per day for three to four people easily.

5 gal buckets filter system

Planning Ahead

If you plan ahead for this, you can buy pool filter sand and activated charcoal for aquariums. Buy four clean buckets with lids and a spigot, and put it up to be assembled for emergencies.

I actually bought a couple of ceramic filters and spigots that are designed for using two 5-gallon buckets. The filter fastens to the lid/bottom of a bucket and the bottom bucket has a spigot. That simple.

ceramic water filter

They cost about $30 for each filter/spigot set, and I’ve had them stashed for about 10 years or so.

The ceramic filters are usable pretty much forever. You just have to clean them periodically by brushing them clean. They are supposed to be a one-and-done setup, where you can pour whatever water in the top bucket and it comes out clean.

I planned that if I really ever had to use them, that I would do a gravel and sand bucket pre-filter system to make the ceramics last longer.

You can make as large of a sand and gravel system as you want, and the last step goes through these ceramic filters. The ceramic filter is supposed to be better than activated charcoal. Hopefully, if I ever need it, that’s an accurate statement from the manufacturer.

Here’s a video using a ceramic filter:

DIY Emergency Water Filter / Filtration System for $35 SHTF Berkey


The reality is that you need to plan ahead for a lot of things. I’ve had many certain items put up for years. They won’t go bad. They’re paid for and don’t eat anything.

If I never need them, I’ll be perfectly happy. But if a time ever comes when they are needed they will be invaluable.

If you can make clean water in a time when no one else has any, you can get anything you want for it.

You will also have to protect it too, just like anything else. If, and when, these times ever come, food and water will be as much of a concern as protecting it from bad guys that want to take it from you.

10 thoughts on “How to Make a Water Filter in a Barrel”

  1. Great article with lots of good tips. Are the grey Lowes buckets food grade? You can get frosting buckets from bakeries, sometimes free.

  2. Well done and great information.
    In my area of California, they are so afraid of mosquitoes and west Nile virus that it is not permitted to have rain catch systems. But I am printing this information and keeping it for just incase.

  3. If your using “Totes” to catch the rainwater in you might consider Guppies (mosquito fish) to keep down the bugs. Some people would not like this idea because fish might pee in the water??? Any way I loved the information you have provided for people who are looking ahead.

    1. Yes, this is my question, I am trying to get a feel for the flow rate. Obviously when there is heavy rain you don’t want water backing up and being wasted, but I don’t really know how fast water would percolate through the sand and charcoal, in other words, how broad the surface would need to be. We get some pretty heavy rain round here, it can be fairly gushing out the downspout. I suppose I will have to test for myself with a small mockup!

  4. You need to update the information you list in this article. Oregon no longer restricts rainwater harvesting on a state level, and in fact has a very informative booklet that is very easy to find. I am about to build in Klamath County, and they allow a cistern and rainwater harvesting in lieu of a well or well contract.

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