Pros and Cons of Mechanical Water Filtration

Part of a solid home preparedness plan involves some sort of water filtration system. All of the prepper stores include water filtration from tablets to straws and some offer some larger systems while others just have a gadget or two for your BOB.

Some are simple in design and some are complicated. From experience, we know that simple is not always enough and the more complex a solution the greater the chance some part of it will fail – Murphy’s Law. So, where does water filtration fit into your survival plan? In this conversation, we look at the benefits and weaknesses of mechanical water filtration so that you can decide if it is a fit for your survival strategy.

Water Filtration – The big picture

Complete water filtration does three things.

  1. First, it filters out the particulate matter down to a specific size. This is what mechanical filtration does.
  2. Secondly, it removes chemicals from the water, such as toxins. This is what chemical filtration does (mostly.)
  3. The third phase is biological filtration, which is a combination of both mechanical and chemical water purification. Complete water filtration addresses particulate matter, chemical and toxins issues, and deals with water organisms.

Dirty water has particles of “things” floating in it. We call that turbidity. After a heavy rain, rivers turn muddy looking. That dirty water is full of turbidity. As the rains stop and river begins to subside, the water clears. It is the force of gravity that helps, and, in a river, the force of the water can suspend objects – even large boulder if the current is fast enough.

water flowing

In a home aquarium, filter pads trap particles as the water passes through the filter material. That is mechanical filtration. In a home water filtration system, such as an Reverse Osmosis System, water is forced through filters that are so small that most particulate matter is trapped. So, mechanical filtration is the physical trapping or removing of particles from water.

The Particle and Water

One of the first questions that you must ask yourself is what is it that you want to filter out of water. Some solid materials – particles – dissolve in water – we call those salts. So, a salt is anything that dissolves in water. Not all salts are safe. Already, we have discovered one weakness of mechanical filtration – The filter is only as good as the smallest piece of toxin it will trap.

So, why not just boil water? One reason is that boiling water only kills the biota – bacteria and other living matter – it does not remove chemicals nor particles. That is not to say that we should not boil water just that it will not help remove the turbidity from the water.

The Ins and Outs of Mechanical Water Filtration

The reality of survival is that we need fresh water. Our bodies, on average, are made up of 70+ percent water. Generally, we can last around 72 hours without water. It is recommended that most adults take in 64 fluid ounces of water per day. That need is to help us flush out the toxins and byproducts of digestion, cellular waste, and to help us make new chemicals so that our body runs as it should.

There are a variety of things that affect how we use water:

  • Those include high temperatures. The hotter the situations the more water we need.
  • The quality of our diet. The higher the salt and sugar content of our food, the more water we need.

Mechanical water filtration can clean freshwater, but only to the limit of the filter. Around my home we have an old well that we use for household water. It was dug some hundred years back and nobody bothered to line it with cement rings.

The house sits in a flood plane so the land around is alluvial deposits – sandy soil. What that means around here is that the well fills up with sand and the water gets dirty. Not great for drinking, bathing, nor laundry. To solve that problem, we have a mechanical filter that separated the bigger particles from the water.

summer rock tree

For drinking, we have an RO system mostly because the well on our neighbor’s property tested positive for methane – a natural result of degradation of organic matter. – i.e. the stuff buried by the river. The wells here, and we have two of them, have never shown a trace of methane, but why chance it. Our second well, is modern and deep. It is what we use to water the gardens, and everything else, but the house.

Our filter system simply runs the water from the old well into a sump that has small weave fiber filters – they look like the green filters you get for you furnace – and then into a second filter that collects the water and pumps it into a storage tank. This helps us have a fresh supply of water that is fairly free of particulate matter. It also allows us to chemically treat a smaller batch of water rather than the entire well.

That system is adjustable, and it outlines the process of mechanical filtration which is the physical trapping of particles in water. The biggest problem with mechanical filtration is that particulate matter can be extremely small – think protozoa, bacteria, and other potentially harmful substances.

lake river cup

Case in point is Flint Michigan where corroded water pipes owned by the city leached particles of lead into the drinking water. This occurred after the water had been filtered and because the city did not wish to spend the small amount of money to protect the pipes – $100/day.

This is also an example of why people need to consider an isolated water supply. The Flint issue was the result of negligence on behave of a city government, but our own governments also worry about the risk of the public’s water supply by both domestic and foreign terror groups.

Note:

  • The big pros of mechanical water filtration is that they are fairly simple to set up and adjust or manipulate to meet your individual needs.
  • The big Con is that a mechanical water filtration system is only as good as the size and condition of the filter material that filters the water.

Another issue with Mechanical Filtration is that it does not always address the chemical makeup of the water. It is one thing to remove sand and turbidity and quite another to remove pesticides.

Some home systems use a coagulation method which traps particles as it falls through the water. This process can be costly and can require a lot of energy and labor to make it effective. So, another con of mechanical filtration can be the ongoing cost.

Some homes use in-line filters that only filter the water that is coming directly into the home. It is much more cost effective to filter only the water that you are going to use. The draw back to in-line filters is that they slow down water flow, but they can be placed on specific lines so that water flows freely where filtration is not needed.

cup of water plastic

Is Mechanical Filtration All you need?

On a daily basis and for many homes a mechanical filter is all that is needed. So long as you test your water regularly. The installation of a UV filter or the use of chemicals can help keep water safe from biological hazards such as protozoa or bacteria.

A mechanical filtration system that utilized charcoal can also help remove some chemicals from water. However, just like in a home aquarium, the charcoal just be replaced about every 30 days. Charcoal also will not remove heavy metals from drinking water. It is good at removing other chemicals but unless it physically traps bacteria it will not protect you from health issues associated with living matter in drinking water.

Charcoal filters are a type of mechanical filter that blends the lines between mechanical and chemical filtration. They are very common in water pitchers, in-line filters, and other types of water filtering devices. They are not practical in large scale filters because of the amount of charcoal needed.

You can certainly add charcoal pads to your filter system. The problem with these is that once the charcoal is wet it has a very short lifecycle. It can sit on the shelf for a million years and be just fine, but as soon as it is wet the clock starts ticking.

As mentioned we use a “rough” mechanical filter that has the sole task of removing the larger particulate material from the old well. For drinking, we use an RO system which is more manageable and more affordable. The big filter makes the well water safe for cleaning and bathing and the RO system gives up plenty of water that is purified for drinking.

man hand water flowing

There are many options available when adding a filtration system to your prepping strategy. Do your homework and address this important issue by asking yourself what you need to filter out of the water – what are you preparing for? In our case, the rough system works well, is easy to maintain, and is affordable.

We have a little solar station there to keep the pumps running when needed. This type of system is not appropriate for all types of residential applications. The big takeaway here is that filtration systems need to fit your need not be something that you try to fit into your lifestyle or prepping needs. We will follow this article up with some additional comparisons so that you can make an informed decision about home filtrations.


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  1. Methane won’t hurt you. You emit methane every day out the back end, along with hydrogen sulfide and lots of other trace elements. If you pump your water and let it sit in a tank for a while, methane dissipates fairly rapidly. I have hydrogen Sulfide gas in my well. The main thing it does is make the water corrosive. It eventually eats up the (metal) pipes and fittings (a cheap faucet from Walmart won’t last 6 months without the chrome coming off, the good ones (read expensive) do the same, it just takes 20 years). There is also Red, Black and Green Algae in the well and pipes. Not a big deal, we have lived with it for 34 years.

    As for RO, you might as well be drinking Distilled water. There are NO trace minerals left in RO water. Your body needs these trace minerals to stay healthy. At my house we use the well water for everything but drinking and cooking. For cooking/drinking we use a “Big Berkey” with the Black Carbon Block filters. They will filter out ALL the heavy metals like lead, Arsenic, etc. (we could have Arsenic in our water, they have it in town). But it leaves the trace minerals that your body needs to function. It also makes the (Very Soft) water taste great. I love our water so much, I hate to take a shower other places like San Antonio where the water is harder than a hammer.

    1. i would like to correspond with another prepper in this area. Especially with someone with some experience and common sense. I live in the brush country out of SanAntonio.

  2. After studying purification of water for the past 11 years, reading the “experts ” white papers on this and that, I’ve decided distilled with carbon filtration either before or after distillation!! All mechanical, nothing electrical…
    Thank you Gaye for another fantastically informative article!
    Be will everyone!

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