Considering ultraviolet water purification for your home? This guide to UV water filters will answer all your questions about how these filtration systems work and when should you be using one.

At least half a million people in the UK source drinking water from a private supply such as a spring, a stream, a well or a borehole. Since these supplies are untreated, sterilisation is needed prior to consumption.

And what better way to sterilise water than using a chemical-free, environmentally-friendly and reliable method like ultraviolet filtration?

How Does UV Water Sterilisation Work?

UV filters use a special lamp that emits ultraviolet light at a wavelength that’s lethal to microorganisms. This UV light destroys the DNA (or RNA in case of viruses) of microorganisms.

Microorganisms exposed to UV lights are rendered harmless, inactive, unable to infect or reproduce. UV filters do all this without the use of chemicals and without altering the taste or chemistry of water.

UV filtration is extremely effective, destroying 99.99% of bacteria exposed to UV lights.

When Should You Use UV Filters?

UV water filters are usually used in the treatment of private water supplies either as a point of use filter or as a point of entry filter.

Aging infrastructures in cities can increase the risk of contamination even of water supplies that are treated with chlorine, therefore, in some cases, it may be indicated to use UV filtration even for the treatment of municipal water supplies.

However, UV filters are predominantly used for the sanitation of private water supplies.

What are the Advantages of Using an UV System?

Compared to traditional water disinfection methods like adding chlorine or chloramine to water, UV filtration has multiple advantages:

  • It’s safe: No chemicals are used, nothing is added to water, and microorganisms cannot develop resistance to UV light;
  • Reliable: UV water purification is a reliable alternative to chlorination;
  • Set-it-and-forget-it type of filtration: UV purification doesn’t require constant monitoring or maintenance. An annual light bulb change is all that’s required;
  • Eco-friendly: Unlike chlorine, which is a pollutant, UV filtration does not result in by-products that harm the environment;
  • No taste alteration: Chlorine and similar disinfectants alter the taste of water; UV purification does not.

Indeed, UV systems don’t alter the taste of water as chlorine does, but they also don’t improve the taste of water like many other filtration systems do (e.g. activated carbon).

Another disadvantage of UV filters is that they only target microorganisms and no other contaminants, so using UV systems in combination with other filtration methods may become necessary.

Unlike chlorination, UV filtration requires electricity, however, the system’s electricity consumption is low.

Even so, UV filters are much better at handling microbiological contamination issues than chlorine. Unlike chlorine, UV filters successfully eliminate even chlorine-resistant bacteria like E-Coli, Giardia, and Cryptosporidium.

What are the Parts of an UV System?

Depending on brand and model, UV systems can be made up differently — some systems may be equipped with more advanced components, while other systems may be so-called bare-bone systems.

The basic components of an UV system, however, are the following:

  • UV bulb/lamp: It’s the element in the system that’s responsible with emitting the UV light that will disinfect the water that’s undergoing treatment;
  • UV quartz sleeve: This cylinder-shaped tube houses the UV lamp and protects it from water;
  • UV chamber: This part houses the lamp and the quartz sleeve, all the while controlling the flow of water through the system;
  • Untreated water inlet and treated water outlet;
  • Controller unit: Whether simple or more complex, the controller unit controls the electrical output of the unit and powers the light needed for purification.

These are the most common and basic elements of an UV filter. Optional elements that some systems may feature include:

  • Solenoid valve: It’s an automatic shut-off mechanism that springs into action if the purification system is not functioning properly, thus, avoiding untreated water flowing through the system;
  • UV sensor: The UV sensor monitors the UV light intensity and triggers an alarm if the intensity is too low;
  • Flow meter: Calculates and displays the real-time UV dose for a certain flow rate.

Another important part in an UV filter — and this part is usually purchased separately — is an UV Prefiltration System, which is a sediment filter designed to remove suspended particles from water.

An UV pre-filter is not optional. All UV systems should be used in combination with a prefilter to remove particles that may block out UV lights. This is important because these particles may shield bacteria and prevent UV lights from reaching them.

Can You Use an UV Filter with Other Filters?

Since microorganisms are the only thing UV filters can eradicate from water, it’s recommended that you pair up UV filters with other filters as well.

Some filter options that you could consider using alongside an UV filter include:

  • Activated carbon filters, which remove chlorine and other contaminants attracted to carbon;
  • Reverse osmosis systems that are best for removing fluoride, heavy metals, asbestos and many other contamination issues;
  • Any other filter depending on the contamination issues with your water supply.

What to Consider When Buying an UV Filter?

Before you buy an UV system, you should consider:

  • Your daily water usage: Assessing your daily water consumption needs can help in sizing your UV filter accordingly;
  • Flow rates: When it comes to flow rates, it’s always better to oversize the UV filter. Flow rates are measured in gallons per minute, and a 6 gallon per minute UV filter is standard for 1-bathroom households;
  • UV dose: UV dose is the amount of UV energy that water is exposed to while flowing through the system. It’s expressed in mJ/cm2, however, unless you’re looking for a commercial UV system, you don’t need more than 10 mJ/cm2, and typical residential UV water purifiers are rated higher than that;
  • Quality of water supply: As we’ve mentioned before, it’s important to make sure that water undergoing sterilisation is free from sediments that might shield bacteria from UV lights;
  • Space considerations: UV systems tend to be bulky if you consider pre-treatment systems as well. Therefore, make sure you have enough space to accommodate the entire setup.

These are the things you should check before investing in an ultraviolet water filtration system whether you’re considering treating well water, rain water or other private water source.

Alternatives to UV Systems

UV systems aren’t the only systems to remove bacteria from water. There are a few other systems you can consider for home water treatment, including:

  • Ceramic water filters: Whether as gravity filters or undersink filters, these filters feature microporous filter media that removes bacteria, viruses, cysts, and other pathogens;
  • Reverse osmosis: RO filters are another great choice when it comes to dealing with microbiological issues.

Water contaminated with bacteria, viruses, cysts should always be treated prior to consumption. Boiling water for at least 5 minutes is another way to sanitise it if you’re in a situation where you can’t use a filter system for the job.

In the next section, you can read more about UV purification and how it works. 

FAQs About UV Systems

Is UV filtration safe?

  • UV filtration protects only from viruses, bacteria, cysts and other microorganisms. Treating water with UV lights is a safe and reliable method to get rid of disease-causing pathogens. With that said, UV filtration does not remove other contaminants from water that may be a potential threat to your health (e.g. heavy metals, chlorine, etc.).

What happens if the power goes out? How does the UV filter work then?

  • Modern UV systems are equipped with a Lamp-Out-Circuit (LOC), which, in case of power outage, will notify you of a power failure by sounding an alarm. You should not continue using water in case of a power outage.

Can I turn off the UV lamp while not in use?

  • You could, however, you ABSOLUTELY SHOULDN’T. The UV lamp is designed to be left on at all times and turning it on and off could cause premature lamp failure, therefore, we recommend leaving it on even when you’re not using water.

Is the UV lamp exposed directly to the water?

  • No, the UV lamp is not exposed directly to water. Instead the UV lamp is protected by a clear quartz sleeve, which allows UV light to pass right through and penetrate the water.

Will flow rates decrease because of sediment filters and/or activated carbon filters?

  • Every time water must pass through a filter media, flow rates will slightly drop. Therefore, if you’re using an UV pre-filter or you’re using UV filtration in combination with other filter systems, you may notice a slight drop in water pressure.

Final Thoughts…

Ultraviolet filtration can be a great alternative to chemical water disinfection of private water sources. It’s a completely safe way of ensuring that the water you drink or use in your household is free of microbiological contaminants.

We hope that the information in this guide will help you pick the best filter system for your home.