Viking water-saving cisterns: ecological and economic options
Introduction: why water consumption matters when choosing taps
Most people focus mainly on design, surface finish, and price when buying a bathroom tap. Water consumption? It was rarely considered – at least not a few years ago. Today the situation has changed. Water and heating prices are rising, the European Union legislation is gradually tightening requirements for appliances including fittings, and more and more households are looking for real, long-term savings. A tap that looks the same as the one next to it can consume tens of euros more or less per year – depending on whether it has built-in saving features or not.
Viking taps belong to the solid mid-range category of accessible bathroom and kitchen fittings. They are not luxury German brands priced at 300 euros per piece, nor are they no-name products without certifications. This mid-range category occupies a large part of the market – and it is precisely here that it makes sense to consider saving technologies, as they represent real value for a reasonable additional cost. In this article, we will look at which specific technologies save water, how they work, what to expect from them in practice, and how to make a choice when selecting.
Basic terms: flow rate, pressure and water consumption in numbers
Before we move on to the actual technologies, it is important to clarify a few basic terms that are repeatedly mentioned when talking about saving taps.
Water flow – what do liters per minute mean
The flow rate of a tap is given in liters per minute (l/min) or liters per hour (l/hour) at a reference pressure, usually 3 bar. A standard sink tap without any flow limiter has a flow rate of around 12–18 l/min. A shower tap can have even more. Saving taps with an aerator or flow meter operate with values of 4–8 l/min, while the subjective comfort remains preserved thanks to air mixing in the water stream.
To give you an idea: washing your hands for 30 seconds with a standard tap at a flow rate of 15 l/min consumes about 7.5 liters of water. The same operation with a saving tap at 6 l/min consumes only 3 liters. That is a saving of 4.5 liters per one hand wash. If we calculate this for a four-person household with two hand washes per day (only at the sink, not including the shower or cooking), we get a saving of more than 13,000 liters per year – from just one tap.
Water pressure and its influence on flow
The flow rate of a tap also depends on the pressure in the pipes. In apartment buildings in Slovakia, the pressure usually ranges between 2 and 5 bar, while in houses with their own well it can be even lower. Saving aerators and flow meters are designed to work stably across the entire range of normal pressures – so that they do not over-flow at 4 bar and do not have too weak a flow at 2 bar. Some premium types use constant flow regulators for this purpose, which maintain the flow at a set amount regardless of pressure fluctuations.
Aerator – the simplest and most accessible saving technology
An aerator is a small insert that is screwed into the outlet of the tap. It contains a fine mesh or several overlapping meshes and a diffuser that mixes air into the water stream. The result is a soft, "velvety" water stream that appears more voluminous than it actually is. The hand perceives it as full pressure, although the actual flow is significantly lower than without an aerator.
How an aerator works technically
Water comes from the tap under pressure, passes through the first mesh, which evenly distributes it. Behind the mesh is a chamber with side openings through which air is drawn in (or air is directly mixed in a closed diffuser). The resulting mixture of water and air forms a homogeneous, white stream that feels pleasant on the skin and does not splash when hitting the hands. The flow rate drops from 12–15 l/min to typically 4–8 l/min, while the subjective comfort remains the same or is even better – especially due to the smoothness of the stream.
Aerators are manufactured in several thread sizes: most commonly M22 (external thread, for most sink taps), M24 (also common), and M18 (smaller, for some kitchen and specific taps). When replacing with a saving model, it is therefore important to check the size of the original aerator – this process is described in more detail in the article Dimensions and connections of Viking taps: what to check before purchase.
Flow rates of aerators in practice – specific values
There are aerators on the market with the following flow rate classifications:
- Standard aerator: 8–12 l/min – mild comfort, no significant saving
- Saving aerator: 5–7 l/min – a good compromise for most households
- Highly saving aerator: 3.5–5 l/min – ideal for toilets and sinks, where water is used for short periods
- Laminar aerator: 3–5 l/min, but without air bubbles – a clean, transparent stream, suitable for laboratories, healthcare facilities, or places where water is used for precise dosing
Important practical note: very low flow (below 4 l/min) can be problematic for shower taps or taps with a built-in water heater – the heater may not start if the flow does not reach its minimum threshold (usually 2.5–4 l/min). Before installing a highly saving aerator, check what minimum flow your heater requires.
Constant flow regulator – stability regardless of pressure
Where a standard aerator simply restricts flow through a physical obstacle (mesh), a constant flow regulator – sometimes also called a flow meter or flow regulator – uses a spring mechanism with an elastomer membrane. When pressure rises, the membrane compresses and narrows the flow cross-section, thus compensating for the higher pressure. At lower pressure, it opens more. Result: the flow remains constant – for example, exactly 6 l/min – regardless of whether the pipe has 2 bar or 5 bar.
This has practical significance mainly in apartment buildings, where water pressure fluctuates according to the daily load on the network – in the morning, when everyone is showering, it drops, in the afternoon it rises. Without a regulator, you would have a weak flow at low pressure and too much water at high pressure. With a regulator, comfort is balanced throughout the day.
Constant flow regulators are either mounted directly into the body of the faucet (built-in solution, installed by the manufacturer at the factory), or as a separate element behind the aerator or in front of the faucet on the supply. They have standardized sizes and can be purchased as accessories for most standard sink faucets.
Thermostatic faucets and their role in water saving
When we talk about water saving, most people think of aerators. Thermostatic faucets, however, are much more effective in terms of real hot water and energy savings – and that is due to a simple reason: they eliminate the waiting time for the right temperature.
Why a standard lever faucet wastes water
Typical bathroom situation: in the morning, you get up and go to wash. You turn the lever faucet to hot water. Until the hot water from the boiler or tank reaches the pipe to the faucet, cold water is flowing from the outlet – and you are pouring it down the drain, because you don’t need it. It depends on the length of the pipe and the water temperature: in a standard apartment, it can take 20–60 seconds, in a house with a longer pipe system even 2 minutes. At a flow rate of 8 l/min, this means 16–96 liters of wasted water per day – for one person, for one wash.
A thermostatic faucet remembers the last set temperature and immediately adjusts the mixing at the next use. This does not shorten the time it takes for hot water to arrive from the boiler (this depends on the hydraulic layout), but it eliminates repeated searching for the right temperature with the lever – and reduces the amount of cold water you waste while finding a comfortable temperature. In combination with hot water circulation (or tracing cable), it is the most effective solution.
More on when a thermostat is worth it and when a lever faucet is suitable for you can be found in the article Lever vs. thermostatic faucet Viking: which one suits your case.
Ecostart function – start with cold water
Some Viking lever faucets (also in the general mid-range category) have a function called Ecostart or Cold Start. The lever in the middle position starts cold water – to get hot water, you have to consciously move the lever to the left. It may seem like a small detail, but in practice it is effective: most short tasks (brushing teeth, quick hand wash) do not require hot water, and if the faucet is not currently mixing, it does not stimulate the boiler or tank to heat cold water into the pipe. Manufacturers report savings of 5–10 % on water heating just from this feature.
Saving technologies for shower systems
With a shower system, saving options are different from those for a sink – the flow rate of the shower is in a different range and the usage time is much longer. Here, a combination of several elements plays a role.
Showerhead with low-flow technology
A standard showerhead has a flow rate of 9–15 l/min. Saving models operate at 6–8 l/min, some even at 4.5–6 l/min with air injection technology directly in the head. Unlike a sink, where you can compensate for low flow by extending the washing time, with a shower, 7 minutes at 6 l/min is just as effective as 7 minutes at 12 l/min – you get just as clean, with a 50 % saving.
The Viking shower system itself does not determine the flow rate of the head – this depends on the combination of pressure, head, and aerator (if built into the head). However, a system with a constant flow regulator on the inlet or with a limited flow in the body has an impact on the maximum possible flow of the system.
Stop button on the shower – a simple element with a big impact
Some shower sets have a stop button (eco-pause) on the handheld head. It allows you to temporarily interrupt the flow without moving the system. Typical use: you lather up, press stop, and open again only when rinsing. The temperature on the system remains set, so you don't have to recalibrate. According to real measurements, a person can save 10–15 liters per shower in this way – with daily use, this amounts to 3,650–5,475 liters per year per person.
Thermostatic shower system – long-term saving
A thermostatic shower system sets the temperature precisely to the degree – usually with an accuracy of ±1 °C. This eliminates the need to search for the right temperature with each use and significantly shortens the time of cold (or insufficiently warm) water running before the shower. In practice: with a thermostat, you press the start and after 5–10 seconds the temperature is correct. With a lever system with hot water running further, it can take 30–90 seconds of "searching".
Water-saving labels and standards – what they mean in practice
The European EcoDesign directive and regulation No. 1753/2015 on energy efficiency labeling introduce for fittings (including taps) a classification system similar to energy labels for appliances. Since 2021, a new label format has been in effect for sink and shower systems as well.
Water-saving classes WRAS and EU Water Label
The EU Water Label classifies taps into classes A to E according to flow rate and energy consumption. Class A corresponds to a flow rate below 6 l/min, class B is 6–8 l/min, class C is approximately 8–11 l/min, and lower classes correspond to standard or above-standard flow rates. Taps with class A or B are labeled as water-saving and are one of the main indicators to focus on when purchasing.
In practice: a standard Viking tap without special features typically corresponds to class C. With a replaceable water-saving aerator, it moves to B, with a flow regulator to A. It is important to know that this label is not mandatory for all manufacturers on the Slovak market – therefore, you should monitor the technical parameters directly in the datasheet, not just the label on the box.
WELL certification and health safety requirements
Aerators with very low flow rates (below 3 l/min) can under certain conditions create an environment for the growth of Legionella bacteria, if the water temperature does not drop below 20 °C and does not exceed 60 °C. This is why in some countries, special antibacterial aerators with an integrated filter that is periodically replaced are recommended for health and social facilities. For a standard home bathroom, this risk is not relevant, but in recreational buildings where the tap stands unused for several weeks, you should consider this.
Selecting the right combination – real-life scenarios
Every household is different. The following scenarios are based on real situations we repeatedly encounter when selecting fittings.
Scenario 1: Starter apartment, 2 people, 80 l water heater
Situation: a small apartment with a central electric water heater, short piping, pipe pressure 3–4 bar. Goal: maximum saving with minimal costs. Recommendation: lever sink tap with built-in Ecostart mechanism and a replaceable 5 l/min aerator. For the shower system, a standard lever with a 7 l/min flow showerhead and a stop button is sufficient. An investment in a special thermostat would only pay off after 8–10 years in such a short piping system, which is borderline.
Scenario 2: Family house, 4 people, 200 l tank, distant bathroom
Situation: a two-story house, hot water tank in the basement, main bathroom on the upper floor, piping 8–12 m. With each start of hot water, 30–60 seconds of cold water flows. Goal: eliminate hot water losses. Recommendation: Viking thermostatic shower system + circulation pump for the hot water loop. If circulation is not possible for some reason (wrong hydraulics), at least a thermostat with stop function and a bucket to catch the cold water (a real-life measure – the water is used for toilet flushing or irrigation).
Scenario 3: Rented apartment / recreational cabin
Situation: a property used intermittently, different users. Goal: resistance to vandalism, minimal consumption even with improper use. Recommendation: taps with built-in fixed aerator (not replaceable, because someone might steal or damage it), built-in constant flow regulator inside the body, thermostatic tap with maximum temperature locked at 38 °C (protection and saving at the same time). Thermostats with mechanical maximum temperature locking are a common part of hotel and apartment inventory.
Economic calculation: how much you actually save
Abstract numbers about savings are nice, but a concrete calculation is more convincing. Let's look at a real case of a four-person household in Slovakia.
Calculation assumptions
- 4 people, each showering once a day (7 minutes)
- Each person washes their hands 6 times a day (30 seconds)
- Water + sewage price: 3.50 €/m³ (typical average in Slovakia 2024)
- Water heating cost: 0.28 €/kWh (electricity), heating 1 m³ from 10 °C to 55 °C = approx. 14.7 kWh → 4.12 €/m³ of hot water
Consumption without saving elements
Shower: 4 people × 7 min × 12 l/min = 336 l/day = 122.6 m³/year
Hand washing: 4 × 6 × 0.5 min × 15 l/min = 180 l/day = 65.7 m³/year
Total: approx. 188 m³/year, of which hot water is about 60 % → 113 m³ hot, 75 m³ cold
Water costs: 188 × 3.50 = 658 €/year
Heating costs: 113 × 4.12 = 465 €/year
Total: 1,123 €/year
Consumption with saving elements
Shower (7 l/min, stop button → -1 min effectively): 4 × 6 × 7 l = 168 l/day = 61.3 m³/year
Hand washing (aerator 5 l/min): 4 × 6 × 0.5 × 5 = 60 l/day = 21.9 m³/year
Total: approx. 83 m³/year, hot water 60 % → 50 m³ hot
Water costs: 83 × 3.50 = 291 €/year
Heating costs: 50 × 4.12 = 206 €/year
Total: 497 €/year
Saving: 626 € per year, which is more than 55 %. Investment in replacing aerators, shower heads and possibly a thermostatic mixer is in the range of 80–250 € depending on the chosen products. Payback period: 2–5 months.
These numbers are naturally model-based and depend on specific habits, water and energy prices in a given region, but they are roughly accurate and correspond to what experienced plumbers and energy consultants report from their practice.
How to choose the right combination for your case
The choice of a specific solution depends on several factors. Here is a practical approach to how to proceed:
- Find out the pressure in your pipes. Low pressure (under 2 bar) limits the choice – very restrictive aerators may give a weak flow. High pressure (over 4 bar) indicates the need for a constant flow regulator.
- Determine the length of the hot water distribution. If the water heater or tank is close to the faucet (up to 3 m), a thermostat provides less benefit than with a long distribution.
- Consider the household habits. Long showers = invest in a saving head. Frequent short hand washing = an aerator will provide quick payback.
- Check the type of heater. A flow heater has a minimum required flow – do not use an aerator with a flow lower than this threshold.
- Do not forget maintenance. Aerators get clogged with limescale – cleaning every 6–12 months is necessary. Details can be found in the article Cleaning and maintenance of Viking taps: how to extend their lifespan.
Ecological aspect: water is not inexhaustible
Economic savings are important, but the ecological context is also worth attention. Slovakia belongs to countries with relatively good surface water resources, but climate change complicates the situation – dry summers since 2017 repeatedly cause problems with reservoir levels, pressure in the water supply network and increased consumption in summer. Municipal water companies respond by increasing prices, but also by infrastructure investments, which are ultimately reflected in the sewage fee.
Every cubic meter of water saved in a household means less energy spent on water treatment to drinking standards, less energy for pumping into the network and less load on wastewater treatment plants. A saving bathroom faucet is therefore not only an economic measure – it is a small, but real contribution to the sustainability of the water management system.
Moreover, in the construction or renovation of a house, some state support programs (ŠFRB, Green Home and similar) today also consider water-saving fixtures as part of the overall assessment of green measures. Although this aspect is not yet regulated as strictly in Slovakia as in some EU countries, the trend is clear.
Installation and replacement of saving elements
Replacing an aerator is simple and can be done by anyone without professional knowledge. You need only an aerator key (or a flat key with a rubber coating), a new aerator of the correct size and 5 minutes. The procedure is described in detail in the article Installation of Viking water tap step by step, where you will also find instructions for the installation of the entire tap.
A constant flow regulator is a bit more demanding – it is usually mounted before the tap on a corner or straight valve, or directly into the body of the tap. When installing into the pipe, it is necessary to close the water supply and check the tightness after installation. If you are not sure about the procedure, we recommend consulting an experienced plumber.
Replacing the entire tap with a model with integrated saving elements is a more complex task, but it is still a routine job that a plumber can do in 1–2 hours. Before choosing a new tap, check the dimensions, type of connection and center-to-center distance – these parameters are key and their overview can be found in the article Dimensions and connection of Viking taps: what to check before purchase. For long-term faults or cartridge sealing, refer to the article Replacement of sealing and cartridge in Viking taps.
Most frequently asked questions (FAQ)
Will a saving aerator also reduce water pressure when showering?
It depends on the situation. An aerator on a sink tap has no effect on the shower circuit – these are separate outlets. There are no aerators on shower taps, saving is ensured by the shower head. If you feel a pressure drop on the sink after installing an aerator, it is a common phenomenon – the flow is lower, but if the aerator is set to 5–6 l/min and the pressure in the network is at least 2 bar, the flow should still be comfortable. At a pressure below 1.5 bar (some older apartment buildings), a 4 l/min aerator can be really weak – in that case, we recommend an aerator with a 6 l/min limit.
How often should an aerator be cleaned?
In areas with harder water (most of Slovakia has hardness of 15–30 °dH), we recommend cleaning every 6 months. Limescale can be easily removed by soaking in vinegar or citric acid for 30–60 minutes. You know it's time to clean when the water flow becomes uneven, splashes sideways or generally decreases. More details in the article Cleaning and maintenance of Viking taps: how to extend their lifespan.
Is a thermostatic tap significantly more expensive than a lever one?
In the category of Viking taps, the price difference is roughly between 30 and 80 euros – a thermostatic model is more expensive. With a long hot water distribution (5 m and more), this investment pays off in 1–2 years from the saved water and energy. With short distributions or a water heater directly in the bathroom, the payback period is longer and a lever tap with a good aerator can be a more economical choice. A more detailed comparison can be found in the article Lever vs. thermostatic Viking tap: which is suitable for your case.
Can I mount a new saving aerator on an old Viking tap?
In most cases yes. Aerators are standardized and there are adapter kits for different thread sizes. You can buy either a precisely dimensioned aerator (M22×1 external thread, M22×1 internal thread and so on), or an adapter kit with multiple transitions. The only exception are old taps with non-standard or heavily rusted threads – in that case, replacing the entire tap may be more economical than repair. How to recognize faults and the condition of the tap is described in the article Common Viking tap faults and how to eliminate them.
Does an aerator affect water quality (hygienic aspect)?
In normal household use, an aerator is not a hygienic problem as long as it is regularly cleaned. Problems with Legionella, which some sources warn about, are relevant only in specific conditions: low temperature of hot water circulation (20–45 °C), long water stagnation in pipes and use in a healthcare environment. In a normal household bathroom, where the tap is used every day and the hot water temperature is above 55 °C, this risk is not relevant. Clean the aerator regularly and use the tap normally – that is all the prevention needed.
Does it pay off to replace aerators in a new building where the taps are new?
It depends on what type of aerator is originally installed. Many developers and construction companies install radiators with standard aerators of 8–12 l/min – price is secondary to them, they only solve functionality and delivery time. If you find out that your new radiator has a flow rate above 8 l/min (simply measure it: catch the water in a container for 30 seconds and double it), replacing it with a 5 l/min aerator (price 3–8 €) is one of the most direct and fastest-returning investments in your entire apartment.
Conclusion: small changes, big results
Water savings in the bathroom are not about sacrificing comfort. A well-designed system – combining a water-saving aerator, flow regulator and possibly a thermostatic valve – will provide the same or even better subjective experience of use while significantly reducing annual consumption and costs. For a four-person household, this means savings in the hundreds of euros per year and thousands of liters of water.
Valves Viking from the category on atria.sk offer a solid foundation for these modifications – either with integrated water-saving features or as a base for aerator replacement and additional accessories. If you are unsure about the choice, more information on how to choose valves according to specific parameters can be found in the article How to choose Viking water valves for the bathroom and kitchen, and if you have questions about common uncertainties, answers are collected in the article Frequently asked questions about Viking water valves.
Do you have a question about this topic?
Having trouble deciding or dealing with a specific situation in your household? Write to us – we are happy to help.