What water pressure do taps need and what to check before purchasing
What water pressure do taps need and what to check before buying
When a customer is choosing a new tap, they usually focus on design, surface and price. Water pressure is almost never checked – and this is one of the most common reasons why a new tap doesn't work properly right after installation or starts dripping after a few months. I've seen dozens of cases where someone bought a quality thermostatic tap for a house with gravity heating and then was disappointed that the thermostat didn't react at all – simply because the pressure in the pipes was too low for the thermostatic mechanism to work reliably.
In this article, we'll look at water pressure in detail, from basic physical concepts through practical measurement to specific values you should know before buying any tap. In addition to pressure, we'll also cover other things worth checking before you reach for your wallet – water hardness, connection diameters, existing piping and compatibility with heating.
Basics: what is water pressure and why it matters
Water pressure in a home installation is given in bars (bar) or in megapascals (MPa). For practical purposes, it holds: 1 bar = 0.1 MPa = 10 m water column. In other words, if you have a water tank placed 30 meters above your tap, you have a static pressure of 3 bars. In a city network, pressure usually ranges between 3 and 6 bars, in some areas up to 8 bars during regulation failures.
Two values are crucial for taps: minimum operating pressure and maximum allowable pressure. Minimum pressure is the limit below which the tap does not work properly – the cartridge cannot be smoothly adjusted, the thermostat does not react, the aerator does not form an even jet. Maximum allowable pressure is the limit above which damage to seals, cartridge or even the body of the tap is possible.
Minimum operating pressure by type of tap
Not all taps have the same requirements. A simple single-lever tap with a ceramic cartridge can work from 0.5 bar, sometimes even a bit less. Thermostatic taps usually need at least 1.0 bar, and some thermostats from European manufacturers require even 1.5 bar for reliable temperature regulation. Taps with water-saving functions (e.g. with an aerator with a perlator insert or with a flow restrictor) can have higher pressure losses and their actual performance at low pressures drops significantly.
Approximate minimum pressures by type of tap:
- Single-lever tap (ceramic cartridge): 0.5 – 1.0 bar
- Two-handle tap (rubber seal): 0.3 – 0.5 bar
- Thermostatic tap: 1.0 – 1.5 bar (some models up to 2.0 bar)
- Tap with electronics / contactless infrared sensor: 1.0 – 2.0 bar + power supply
- Tap with integrated heating (boiler in the body of the tap): 0.3 – 1.5 bar (depends on the model)
- Shower tap with massage functions / under-bench: 1.5 – 3.0 bar for full effect
Difference between static and dynamic pressure
Most people make a mistake here. Static pressure is the pressure in a closed pipe – when everything is closed. Dynamic pressure (or operating pressure) is the pressure that actually appears when you open the tap and water is flowing. The difference can be significant: I have a client in a family house where the static pressure is 4.2 bar, but when the shower, sink and tank are used simultaneously, the dynamic pressure drops to 1.8 bar. Exactly at this level, the thermostatic shower tap works stably, but when another outlet is opened somewhere in the house, the thermostat starts "dancing".
Therefore, when choosing a tap, it is important to know the dynamic pressure – i.e. the pressure during real use. Static pressure on paper is a nice number, but it is not the number you should choose a tap based on.
How to measure water pressure at home yourself
You can measure pressure easily with a manometer, which you can buy in any garden store or online for a price of 5–15 euros. Most manometers have a thread of 1/2" or 3/4" – direct connection to the shut-off valve after the water meter, to the garden tap or directly to the tap outlet with an adapter.
Procedure for measuring static pressure: close all outlets in the house, connect the manometer and read the value. Procedure for measuring dynamic pressure: open all outlets you commonly use at the same time (shower + sink + WC flushing), and read the value at full flow. This second step is more important for choosing a tap.
High pressure: when is it a problem and what to do about it
High pressure – above 6 bar – is just as problematic as low pressure. Taps are typically designed for a maximum pressure of 10 bar (some higher-quality ones are certified for even more), but long-term operation at the 8–10 bar limit quickly degrades seals, cartridges wear out faster, and there is a risk of bursting flexible supply hoses.
In practice: many panel buildings and older apartment blocks in cities have a supply pipe pressure of 5–7 bar. If water "sprays" when you open a tap and forms a noisy jet, it is a sign that the pressure is at the upper limit. The solution is clear: pressure-reducing valve, which is installed after the water meter and sets the pressure to 3–4 bar. It costs around 20–60 euros and will extend the lifespan of the entire installation, including taps, the washing machine, and the dishwasher.
Signs of excessively high pressure
- Noisy water flow, "noise" in the pipes
- Water hammer effect when quickly closing taps
- Frequent dripping of taps (worn seals)
- Bursting of flexible supply hoses
- Shortened cartridge lifespan
Low pressure: gravity systems and special taps
Gravity systems – where water flows from a tank located above the bathroom (typically a boiler room or an attic tank) – have a pressure of only 0.1 to 0.5 bar. For this case, there are special "low-pressure" taps, which are designed to work even with minimal pressure difference. Their internal parts – especially the cartridge – have less resistance and a larger flow diameter.
A standard ceramic cartridge from a regular tap will start to work irregularly at pressures below 0.5 bar: either it won't flow at all, or it will flow uncontrollably and cannot be regulated. Therefore, you can never take any arbitrary tap into a gravity system. The manufacturer must explicitly state in the technical specifications that the tap is suitable for low pressure (low pressure).
An interesting example from practice: a customer renovated an old rural house and kept the original tank on the roof. He bought a modern single-lever tap for the bathroom, the installation went smoothly, but the cartridge could not be regulated – either cold or hot, nothing in between. The problem was clear: the pressure was only 0.3 bar and the cartridge could not handle it. Solution: installation of a pressure-boosting pump (hydrofor) or replacement with a tap certified for low pressure.
Pressure balance: cold vs. hot water
Another technical detail that is rarely discussed: taps, especially thermostatic ones, require that the pressure of cold and hot water be balanced. The ideal situation is a ±20% difference. If the pressure of cold water is 4 bar and hot water is only 1 bar (for example, with instantaneous water heaters or with a distant location of the tank), the thermostatic tap will not be able to regulate the temperature properly – it will strongly favor the cold side.
This situation most often occurs when combining a public water supply with high pressure and a domestic storage water heater, where hot water comes through long pipes with pressure losses. Solution: a pressure-reducing valve on the cold supply, set to the same pressure as the hot water.
What to check before buying a tap: complete checklist
Water pressure is only one of the things you need to check. Here is a systematic overview of what you should know before you choose a specific tap.
1. Dimensions of the connection point
Before anything else, find out what the dimensions of the existing supply hoses or pipes are at the installation site. Standard taps have a supply of 1/2" (basin, sink, bidet), bathtub taps also have 1/2", some older installations and outdoor taps have 3/4". Changing the diameter is possible via reducers, but you need to know this in advance. More on this topic can be found in the article Dimensions and tap connections: what do 1/2", 3/4", and center distance mean.
2. Center distance between holes
For two-hole taps (bathtub, some basin taps), the center distance between the cold and hot supply is key. The European standard is 150 mm, but in older homes and some imported installations you can find 120, 160 or other dimensions. Measure before buying, not after.
3. Outlet height and type of mounting
A deck-mounted tap sits directly on the basin or sink and requires a hole in the worktop or sink. The standard size for a deck-mounted tap is 35 mm, some models have 32 mm. A wall-mounted tap, on the other hand, requires installation of the piping in the wall. If you are changing the type of mounting, it is a major construction job. More on this can be read in the article Wall-mounted vs. deck-mounted tap: which is suitable for your bathroom.
4. Type of hot water heating
This is crucial for choosing between a standard and a thermostatic tap, as well as for choosing the flow rate. Storage water heaters supply hot water with relatively stable temperature. Flow-through heaters are sensitive to flow – if you open the tap to maximum, the water may be cold (the heater cannot keep up), if you open it only slightly, it may be boiling. Flow-through heaters therefore require taps with flow restrictors or special solutions.
5. Water quality and hardness
Hard water – that is, water with a high content of calcium and magnesium – causes limescale deposits in the cartridge, aerator and on the surface of the tap. If you have water hardness above 25 °dH (German degrees of hardness), I recommend investing in a water softener or filtration system, or choosing taps with ceramic expansion cartridges certified for hard water. Aerators should be cleaned every 3–6 months in hard water conditions.
6. Surface finish and environment
The bathroom is a humid environment, the kitchen is exposed to grease. Not every surface of a faucet is equally resistant. Chrome is a classic – durable, easy to clean, but with hard water, water spots are visible on it. Satin (brushed stainless steel surface finish) hides fingerprints better, but with inappropriate cleaning agents it loses its shine. Black matte is trendy, but the most demanding in terms of maintenance – every drop leaves a mark. More details can be found in the article Surface finishes of faucets: chrome, satin, black matte – differences and durability.
Specific tips for common situations
Apartment in a panel building: typically 3–5 bar
In panel buildings, there is usually a public water supply network with a pressure of 3–5 bar – an ideal range for any standard faucet. The issue is more about water hardness (most cities in Central Europe have medium hard to hard water, 15–25 °dH) and noise problems from water hammer due to hydraulic shock. In these cases, a good choice is a wall-mounted faucet such as 946487 wall-mounted faucet LOOP or wall-mounted faucet ARKO in satin finish. For bidets, a practical choice is bidet faucet ARKO in chrome with drain kit, which includes a drain set – no need to buy additional accessories separately.
Detached house with a hydro pump: pressure may vary
A private well or cistern with a hydro pump (hydrofor) usually has a pressure set between 2–4 bar, but it may temporarily drop during fluctuating consumption. If the hydro pump is properly set and the membrane tank is large enough, the faucets will not fall below the working pressure. Problems arise with old hydro pumps with small membrane tanks – the pressure fluctuates between 1–4 bar, which puts stress on the cartridges. Solution: a larger pressure tank (>50 liters for a typical 3–4 person household).
Old house with a gravity tank: less than 0.5 bar
This is the most problematic scenario. The only reasonable solutions are: a) installation of a pressure-boosting pump, b) replacement of the tank with a pressurized tank with an expansion vessel, c) purchase of faucets explicitly certified for low pressure. Option c) is the cheapest, but the range of such faucets is limited.
Water flow: liters per minute and aerators
Along with pressure, flow rate is also important – the amount of water passing through the faucet per minute. It is given in l/min or l/hour. A standard sink faucet has a flow rate of 8–12 l/min at 3 bar. Saving aerators limit the flow to 5–6 l/min without significantly reducing comfort (the water is aerated and subjectively feels just as strong). Shower faucets can have a flow rate of 12–20 l/min.
Flow rate depends on pressure – higher pressure = higher flow. Therefore, flow rate is always stated at a reference pressure (usually 3 bar). At lower pressure, the flow rate will be lower. This dependence is roughly linear: a pressure drop from 3 to 1.5 bar means a flow rate drop of about 30–40 %.
Certificates and brands worth paying attention to
Before purchasing, it is worth checking which certificates the faucet has. For the Slovak and European markets, the following are relevant:
- CE: mandatory mark for the European market, basic compliance with safety standards
- DVGW (Germany): one of the strictest certificates for devices coming into contact with drinking water – if the faucet has it, it is a good sign
- KIWA (Netherlands): a similar certificate, recognized throughout the EU
- ETA (European Technical Assessment): less common for faucets, but occasionally found
- Water-label.eu: a voluntary European eco-label for water saving – the higher the class (A+), the lower the consumption
Be cautious of faucets without any certificate from dubious sources – they may contain lead or other harmful substances in the body of the faucet, which can leach into drinking water. This is especially important for kitchen faucets, where water is drawn for drinking and cooking.
Practical approach: how to compile your requirements before purchase
Based on my experience in customer practice, I recommend going through these steps before purchasing any faucet:
- Step 1: Measure static pressure (manometer behind the water meter with all taps closed)
- Step 2: Measure dynamic pressure (during normal consumption)
- Step 3: Check whether the pressure difference ST/TV is less than 20 %
- Step 4: Measure the axis distance of the inlet and the diameter of the mounting hole
- Step 5: Find out the water hardness (from the water utility or with a test strip)
- Step 6: Decide on the type of heating and choose a thermostatic or standard faucet accordingly
- Step 7: Choose the surface finish according to the environment and frequency of cleaning
- Step 8: Check the technical data sheet of the faucet – look for minimum working pressure, maximum pressure, flow rate at 3 bar
Basin taps and showers: pressure and flow are even more important
With basin taps and shower units, pressure is even more critical than with sink taps, because the shower head and hose consume significantly more water. A good shower needs at least 6–10 l/min at a pressure of at least 1.5 bar for a satisfactory experience. Rain showers (so-called overhead showers, diameter 20–30 cm) may require 12–20 l/min and with insufficient pressure they simply do not run fully – water flows only from the center and the edges remain dry.
If you are considering a basin tap, for example the ARKO basin tap in satin finish – this is supplied without accessories, giving you the freedom to choose a shower set according to your preferences and pressure situation. Always check which shower set you want to connect and what its minimum pressure is before purchase.
Bidet taps: a specific case
Bidet taps generally require a lower flow rate than sink taps – 4–6 l/min is sufficient. More important than flow here is temperature regulation – a bidet is used on more sensitive parts of the body and even a few degrees change in temperature is noticeable. Therefore, a thermostatic system or at least a quick-acting single-lever ceramic cartridge is suitable here when pressure fluctuates (e.g., simultaneous toilet flushing).
A practical solution with complete equipment is, for example, the ARKO bidet tap with drain set in satin finish, where the drain set is part of the package – this is an important detail, as it eliminates the need to search for a compatible drain set separately.
Installation and pressure: what to check after installation
After installing a new tap, there are a few things you should check before using it fully. First, check the sealing and tighten the supply lines – when opening for the first time, slowly open the valve and watch for leaks. Second, purge air from the installation – when opening the new tap for the first time, air in the pipes can cause noisy operation. Third, remove and flush the aerator – during a new installation, impurities from the pipes are released and the aerator will catch them.
If you hear hammering in the pipes after installation (water hammer effect), the cause is likely the ceramic cartridge closing too quickly. Some taps have cartridges with slower closing (so-called quarter-turn or 3/4-turn design), while in others it is possible to install a flow limiter on the supply. More about installation can be found in the article Installing a water tap – step by step.
Most frequently asked questions (FAQ)
How many bars is the ideal pressure for a standard bathroom?
For most standard taps, the ideal range is 2–4 bars. At this pressure, the cartridge operates smoothly, the flow is sufficient, and component wear is minimal. If your network pressure is constantly above 5 bars, I recommend installing a pressure-reducing valve after the water meter and setting it to 3–3.5 bars – this will extend the life of your entire installation.
My thermostatic tap does not hold the temperature – can pressure be the cause?
Yes, very likely. Thermostatic taps require balanced pressure of cold and hot water (ideally ±20%) and a minimum operating pressure of 1.0–1.5 bar. If the pressure of hot water is significantly lower (e.g., due to long pipe runs or an old storage tank), the thermostat will not be able to maintain the set temperature. A solution is a pressure-reducing valve on the cold side or replacing the hot water distribution system.
What is a low-pressure tap and how do I know if I need one?
A low-pressure tap is designed to operate at pressures below 0.5 bar – typically in houses with gravity-fed water tanks (roof tank or attic). You can recognize it by the marking in the technical documentation (minimum operating pressure 0.1–0.3 bar). If your pressure at the point of use drops below 0.5 bar, a standard tap will operate unreliably – it will either not flow at all or will not be adjustable.
Can I use a standard tap with a flow heater?
Yes, but with limitations. A flow heater works on the principle that the higher the flow, the lower the temperature (and vice versa). A standard single-lever tap can handle this, but you should know that opening and closing the tap changes the temperature. A better option is a tap with smooth flow and temperature regulation, or a special version for flow heaters with certification for this type of system. A thermostatic tap generally does not work well with a flow heater.
How do I find out the water hardness before buying a tap?
The easiest way: call your water utility or visit their website – most water companies publish current water quality, including hardness. Alternative: water hardness test strips, available for a few euros at a pharmacy or garden center. For precise measurement, a water laboratory analysis is available. If hardness is above 20 °dH, I recommend investing in filtration or softening, regardless of the type of tap.
What to do if after buying a tap I find out that my pressure is too low?
You have three options: a) return the tap and buy a type certified for your pressure, b) install a pressure-boosting pump (hydro-for or flow pump), c) increase the pressure in the system by adjusting the hydro-generator, if you have one. The cheapest option is a), if the seller allows it. Option b) is a permanent solution, but requires an investment of 80–300 euros depending on the pump's performance. Never use a tap long-term below the minimum pressure – the cartridge will wear out much faster.
Conclusion: water pressure is not just a number on paper
Water pressure is a fundamental parameter, without which tap selection makes no sense. It is not enough to know that you have a "normal" pressure – you need to know the exact values of static and dynamic pressure, their balance between cold and hot water, and how they behave at maximum simultaneous consumption. This information will help you avoid the most common mistakes: buying a thermostatic tap without sufficient pressure, selecting a standard tap for a gravity-fed system, or ignoring high pressure that slowly damages seals and cartridges.
The combination of the correct pressure, matching inlet diameter, suitable surface, and certified tap from a reputable manufacturer will ensure that your new tap operates reliably for years without problems. Take a look at the full range of water taps, where you will find models with complete technical specifications – including minimum pressure, flow rate and dimensions – for every type of installation.
Do you have a question about this topic?
Not sure or dealing with a specific situation in your home? Write to us – we are happy to help.