UV lamp in a single-family house. How to choose a UV lamp? What do you need to know?

Is Sterilizing Drinking Water Necessary? When Should We Consider It?

In many Western countries, especially in urban areas, water sterilization using UV lamps is becoming the standard, and installing a lamp emitting ultraviolet rays is considered during the construction stage. Is it necessary? In some regions, absolutely, but claiming that every household should install a lamp may be overstating it.

If we have doubts - it's best to consult the Sanitary Epidemiological Station (Sanepid) for a water test. After providing a water sample, we will receive the results within a few days along with information on how to interpret them. Sanepid should provide basic information based on the water test on whether UV sterilization is worth considering. The primary criterion indicating the need for such sterilization is the presence of bacteria from the E-Coli strain.

This is not the only indication - UV water sterilization eliminates odors from the water supply, including the smell of chlorine or its taste. In this case, if there are no indications of bacteria or fungi in the water - we can consider such a UV lamp as an investment in improving the quality of life, but it cannot be said to be necessary.

What Requirements Does a UV Water Lamp Have? Can Any Water Be Sterilized?

Water must be transparent to be effectively sterilized by UV. Sterilizing dirty water, visually contaminated, is not an option because it is ineffective. Additionally, mechanical impurities could damage the bulb or adhere to the quartz tube in the lamp. Therefore, we always install the sterilizer after the first filters, which are located at the water inlet to the house, never before. These must be mechanical filters, such as string filters, chosen according to needs. In the case of water from the municipal water supply, the water generally meets certain standards, but for well water, a more robust filter may be required.

Another issue is the iron content in the water. In some regions, it is too high - exceeding the level of 0.2 mg/l. If in doubt, additional water tests should be conducted. Regulations require local authorities to provide water from water mains with an iron content not exceeding 0.2 mg/l (this value may vary depending on the country). The problem may arise with water drawn directly from wells - where this level is higher. Most UV lamp manufacturers specify the maximum iron level (defined as safe for the sterilizer) at 0.3 mg/l, but this is already a level that is not optimal for health. In such cases, if we were to use a water sterilizer, we should also install so-called iron removers.

How do we know if the iron level may be too high and we should conduct detailed water tests? The water then takes on a metallic taste and odor, and in extreme cases, it may acquire rusty or orange discolorations.

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How Big Should a UV Water Sterilizer Be for a Single-Family Home?

In practice, for a small single-family home, if it has a classic layout - i.e., one kitchen and one bathroom - a lamp with a power of 30W is often sufficient. We can opt for a larger lamp in such a home layout if there are more people using the water, for example, 4-5 people. Another argument for a larger lamp may be any specific water problems in the region, such as the awareness that the region faces a recurring E-Coli problem, etc.

For a larger layout - with 1 kitchen and two bathrooms - lamps of around 55W are absolutely recommended.
This is how it looks in practice, describing it in a way that is understandable for laypeople and simplified.

However, if we want to go into details - a UV water lamp should be selected so that the ultraviolet radiation dose is at least 400 J/m² in relation to the water flow at the inlet to the house. It is an absolute mistake for people without knowledge to select based on water consumption (e.g., on a weekly or monthly scale), which may be low (e.g., in a holiday home where we do not stay daily) - instead of selecting based on the maximum unit flow rate at the house inlet, converted to l/h or l/min. Also, the lamp's power expressed in Watts should not solely determine the selection because the size and structure of the sterilizer also play a role, allowing for the accumulation of a certain volume of water - which will be subjected to sterilization at a given moment. When providing the above power of sterilizers needed for water sterilization in a single-family home - we only give a range, which may vary slightly depending on the manufacturer. Our point of reference is the NORDIC Tec water sterilizers.

Which UV Water Lamps Should Be Avoided?

It's definitely worth skipping lamps made of plastic or PVC for home use. They should be decent units made of stainless steel. After all, it's about drinking water, and only good-quality stainless steel ensures a material that does not react and does not further contaminate the water. Plastic and PVC are cheaper materials that work well for sterilizing water for ponds or garden ponds.

It is also advisable to avoid lamps that have non-standardized bulbs, of which there are quite a few on the market. This is usually low-quality Asian imports. It's worth having a lamp with a bulb that is easy to replace if it burns out. Before making a purchase, it's a good idea to ask the seller for the lamp's bulb symbol and check online if it is relatively easy to purchase.

Also, pay attention to whether the UV sterilizer has any system indicating a lamp malfunction or the need to replace the bulb. The sterilizer always has a converter (power supply), which should be equipped with a LED signaling system. There are lamps available on the market that signal a lamp malfunction (usually resulting from bulb burnout) with a specific sound signal. In most cases, however, this is done through simple light indicators. In Nordic Tec sterilizers, this is done in a simple and practical way, i.e., on the converter, you can see 2 LEDs, a green one indicating the sterilizer's operation and a red one that lights up when replacement is needed.

Tips for Installing a UV Lamp at Home?

A UV sterilizer should be installed primarily so that we have access to it later - for basic servicing tasks. About once a year, the lamp bulb should be replaced or the quartz sleeve cleaned (which is recommended even more often than once a year) - so it's worth thinking about this when designating the installation location.

Very important tip: When installing a UV sterilizer on the wall and connecting it to the DHW system in the house, as described above, remember that we need to access the lamp from time to time. Turning off the UV lamp and replacing the bulb, especially removing the quartz sleeve protecting the bulb, may cause water loss. To avoid draining water from the entire installation, which would be costly and absolutely pointless, valves should be installed on both sides of the UV lamp (at the inlet and outlet). This will allow us to cut off the sterilizer from the installation in case of any problems and redirect the water through an alternative route. Our photograph illustrates this solution.

In most cases, such a lamp can be installed in any position, i.e., horizontally or vertically, as shown in our photo. However, it's worth connecting the lamp securely to the installation with sturdy reinforcing pipes. The UV lamp should not be mounted with any flexible hoses, which only add extra weight.

Can I Synchronize the UV Sterilizer with the Water Flow or Install a Timer Switch to Save Electricity?

This is a very common question we receive from users or people planning to purchase a UV water sterilization system. The answer is unequivocal - it is not recommended, and we discourage such a solution.
Firstly, such sterilization is ineffective, even for several reasons - the activated UV lamp acts as a barrier for bacteria and fungi, which is practically impossible to overcome. However, these microbes can still develop in front of the lamp, and turning off the lamp can cause them to penetrate our installation, and then new foci of infection develop beyond the UV lamp. Secondly, the bulb reaches its optimal effectiveness only after a few seconds. These first few seconds of flow - which would activate the lamp - represent a significant amount of water that will not be realistically sterilized.
Another reason is the lifespan of the lamp or rather the bulb. The TUV bulb emitting ultraviolet radiation is not a traditional light bulb and is not designed for continuous on-off cycling. It is, however, perfectly suited for continuous operation. Paradoxically, it burns out much faster with too frequent on-off cycles than with continuous operation (even for months). We know the stories of people who experimented with synchronizing the lamp with the water flow in the pressure tank, and the UV bulb lifespan usually shortened to a few weeks (when under normal conditions, the bulb is replaced on average once a year).

A common argument for more frequent lamp shutdown is energy savings. This is understandable, especially in times of rising electricity prices. Therefore, it is worth calculating the expenditure related to electricity consumption before purchasing. For example, the NORDIC TEC 55W lamp has a power consumption of around 60-70W. It consumes about 1.5-1.7 kWh per day, and monthly about 45-50 kWh. This is a monthly expense of no more than 30-40 PLN calculated at market electricity prices. If we talk about a 30W lamp, this cost drops to below 20 PLN per month.

In summary, the UV sterilizer should operate continuously - i.e., 24/7. The UV sterilizer should only be disconnected from the power grid in situations of longer absence exceeding 1-2 days. We discourage turning off the lamp at night, during working hours, when walking the dog, and when nobody is home - and in similar situations. We recommend turning off the UV when going away for the weekend or even for 1 full day - such a procedure will undoubtedly contribute to the bulb's lifespan.

Will UV Water Sterilization Eliminate the E-Coli Problem?

In single-family homes, it most often does - UV sterilization kills 99.9% of E-Coli microorganisms. However, in larger and extensive installations, such as commercial buildings with a larger water network area (e.g., schools, shopping centers, recreational centers, hotels, etc.), it often happens that E-Coli has already created its foci in more distant parts of the installation. Then, despite sterilizing the water entering the installation, E-Coli develops behind the lamp. Such a situation, in addition to installing a UV lamp of the appropriate size, also requires cleaning the installation with an appropriate disinfecting agent based on calcium hypochlorite. However, in single-family homes, due to the less extensive installation and practically all domestic water accumulating in the tank, such situations occur less frequently, and usually, installing a UV lamp should help.

Feel free to check out our catalog of UV lamps, featuring PHILIPS bulbs.