Why does water pressure across the whole flat vary through the day?

Peak Consumption Hours – Morning and Evening

The most common reason for fluctuating water pressure in an apartment building throughout the day is simply that many residents use water at the same time. In the morning from 6–9 AM, everyone is showering and filling kettles; in the evening from 6–10 PM, they're washing dishes, taking baths, and running washing machines.

• The more users on the same riser drawing water simultaneously, the lower the pressure at each individual tap.
• At night and during the day, when consumption is low, pressure usually feels stronger.
• This is a physical phenomenon – water is distributed among all users within a pipe of limited diameter.
• This phenomenon is more pronounced in older buildings where risers have a smaller diameter or are partially calcified.

Floor Height and Riser Pressure Losses

Water pressure naturally decreases with each ascending floor – water must be pumped upwards against gravity, and friction loss in the pipework also increases with longer runs and more fittings. Therefore, residents on higher floors often experience lower pressure than those on lower floors, and they feel the peak hour drop more acutely.

• The higher the floor, the greater the impact of fluctuations in the shared pressure system.
• On lower floors, pressure may remain consistently high even during peak hours.
• If the problem occurs only on the highest floors, it likely points to an issue with the booster pump or riser, rather than a single apartment.

Apartment Building Booster Pump

Many apartment buildings, especially taller ones or those further from the main water supply, have a booster pump (hydrophore) installed to ensure adequate pressure even on upper floors. If this pump operates erratically, is incorrectly configured, or is faulty, the entire building or part of it will experience fluctuating water pressure.

• The pump's automation switches on and off according to the pressure in the tank – if the setting is off, a noticeable pulsing will occur.
• A faulty pressure tank (diaphragm tank) causes frequent pump start-ups and pressure surges.
• Pump maintenance, filter replacement, and setting checks are the responsibility of the apartment association, not the individual apartment owner.
• If you suspect a pump fault, report it to your apartment association's manager or maintenance partner.

City Network Pressure and Water Utility Works

If a building is not connected to a booster pump, apartment water pressure depends directly on the municipal water supply pressure in the street. The water utility regulates network pressure according to regional consumption and elevation differences, and may also intentionally reduce pressure during repair work, emergency localisation, or periods of high consumption.

• Higher consumption in an area (e.g., for summer garden watering) can lower pressure for all buildings in that district.
• Planned works or emergencies in the water utility's pipe network cause temporary pressure drops or interruptions.
• Information on planned works is usually available on the water utility's website or through notification channels.
• If pressure is low throughout the street or in several buildings at once, it is not a problem with the building itself.

Clogged Aerator and Tap Filter

If pressure is weak in only one tap or shower, while everything else in the apartment is fine, the cause is usually local – not system-wide. The most common culprits are the aerator (the mesh at the end of the tap that mixes air with water) or the tap's internal filter, which has become clogged with limescale, sand, or rust particles.

• The aerator can usually be unscrewed by hand, cleaned in a vinegar solution, and reattached.
• Shower and tap filters should be removed periodically and cleaned of limescale, especially in hard water areas.
• If cleaning doesn't help, the problem might be in the tap's ceramic cartridge, which needs replacing.
• This is one of the few water pressure problems an apartment owner can solve entirely independently.

Partially Closed Shut-off Valve

If construction or renovation work has been done in the apartment, it's common for a shut-off valve not to be fully opened after the work is completed. A partially closed valve restricts water flow and creates the feeling that the pressure has generally dropped, although it's simply a narrowed pipe diameter.

• Check the main shut-off valves in your apartment – these are usually located where the water enters or under the kitchen/bathroom sink.
• Old valves can also become stiff or partially jammed on their own, without anyone having touched them.
• Fully opening and closing the valve a couple of times can sometimes free a stuck mechanism.
• If the valve is old and loose, it's worth considering replacing it to prevent future leaks.

Calcified and Ageing Pipework

In Soviet-era buildings where pipework has not yet been upgraded, a common problem is an internal layer of limescale and rust, which reduces the internal diameter of the pipe. Such pipework reacts more acutely to consumption peaks than new pipes with a smooth inner surface, because a smaller diameter means greater flow resistance.

• Old galvanised steel pipes narrow over the years due to sediment, exacerbating pressure fluctuations.
• A similar issue, but from a drainage perspective, is discussed in the article on old cast iron pipes in the sewage system.
• Upgrading the entire building's pipework (riser replacement) is a major project decided by the apartment association, not individual apartment owners.
• Within their own apartment, owners can only upgrade the section they own, if it is technically separable.

Pressure Reducer (Pressure Limiter) Settings

Some apartments or building incoming pipework have a pressure reducer (pressure limiter) installed, designed to protect taps and appliances from excessively high pressure. If this device is incorrectly set, clogged, or faulty, it can cause uneven, fluctuating, or excessively low pressure, which may seem like a building-wide problem, even though it's a fault with a single device.

• The pressure reducer's setting can be adjusted with a special screw or nut, but this should be done by an experienced specialist.
• If taps immediately downstream from the pressure reducer suddenly have low pressure, check this device first.
• Pressure reducers should be serviced periodically, as sediment and limescale can accumulate there too.

Impact of the Hot Water Circulation System

In apartment buildings with central hot water circulation (water constantly flows through the pipes so you don't have to wait long for hot water in the shower), a disruption in the circulation system can specifically affect hot water pressure, leaving cold water untouched. If the problem occurs only with hot water, it's worth checking if the fault lies with the circulation pump or its controls.

• If only hot water pressure fluctuates, but cold is stable, the cause is likely in the hot water system, not the general water supply.
• Maintenance of the circulation system is usually the responsibility of the apartment association or its heating and water maintenance partner.
• See also the guide on cleaning a water heater if the problem seems to be with a private hot water appliance.

How to Measure Water Pressure and What the Numbers Mean

If you want to objectively assess water pressure fluctuations, rather than just by "feel," the easiest way is to install a temporary manometer (pressure gauge) on the tap, which can be bought at a DIY store and screwed onto the tap.

• Measure pressure at different times of the day – morning, midday, evening, night – and record the results.
• Generally, 2–4 bar is considered normal for residential premises, but the exact suitable range depends on the building type and appliances.
• If the pressure is consistently below 1.5 bar, consider having the system checked.
• If the pressure repeatedly rises above 6 bar, there's also a risk to appliances and seals – high pressure wears out equipment faster.

What the Apartment Owner Can Do and What the Apartment Association Does

When solving water pressure problems, it's important to distinguish between what is an internal apartment responsibility and what is a common building responsibility, to direct inquiries to the correct party and avoid wasting time.

• Apartment owner's responsibility: cleaning aerators and filters, checking apartment shut-off valves, maintaining or replacing tap internal mechanisms.
• Apartment association's responsibility: condition of risers, maintenance and adjustment of the booster pump, maintenance of the pressure reducer in common pipework, hot water circulation system.
• Water utility's responsibility: city network pressure up to the building's connection point, planned works and emergencies in the main pipe network.
• If the problem affects multiple apartments simultaneously, inform the apartment association immediately – addressing it as an isolated case will not yield results.

When to Call a Plumber

If you've cleaned the local aerator, checked the shut-off valves, and the problem persists only in your apartment, it's time to call a specialist who can inspect the internal pipework, taps, and if necessary, measure pressure at different points more precisely.

• Pressure is consistently low in only one tap, not cyclically during peak hours.
• You suspect a blockage or limescale build-up in your apartment's pipe section.
• You need an assessment of whether a shut-off valve or tap needs replacing.
• You want to install a new tap or sanitary equipment that requires a professional connection.

Pipework Material and Diameter in Different Buildings

The material and diameter of an apartment building's pipework directly affect how strongly consumption peaks are felt. Newer buildings today mostly use plastic or composite pipes, which have a smooth inner surface and low flow resistance. In Soviet-era buildings, however, galvanised steel pipes are often still in use, whose inner surface becomes covered with limescale and rust over the years, reducing the actual flow diameter, even if the pipe externally appears to be the same size.

If a partial riser replacement has been carried out in a building (e.g., one stairwell has been upgraded, another has not), there can be very different pressure experiences within the same building – stable in the upgraded part, strongly fluctuating in the old part. This is also one reason why neighbours in the same building describe water pressure problems very differently.

• Plastic and composite pipes maintain their original diameter for decades, provided they are not burdened by excessive limescale formation.
• Steel pipes are more likely to require cleaning or replacement over time, as flow resistance increases due to inner surface roughness and deposits.
• In a partially upgraded building, a pressure difference between stairwells can be completely normal, not necessarily a sign of a fault.

Seasonal Factors – Summer, Winter, and Irrigation Period

Water pressure fluctuations are not consistent throughout the year. In summer, when many households also use tap water for garden irrigation or washing around the house, overall consumption in the area increases, and this can lower pressure throughout the street, not just in one building. In winter, temporary pressure fluctuations may occur due to the risk of freezing in certain pipe sections or repair work carried out by the water utility before the onset of severe frosts.

• The summer irrigation season increases overall water consumption in the area and can lower pressure specifically in the evening, when people water gardens after work.
• Planned maintenance work often takes place in autumn and spring, which can cause short-term pressure fluctuations or interruptions.
• If you notice that the problem is strongly seasonal, it's worth noting it down – this information will help the apartment association or water utility identify the cause faster.

Impact of Appliances and Taps on Perceived Pressure

Part of what residents perceive as a "drop in water pressure" is not actually a change in pipework pressure, but a characteristic of the appliances themselves. For example, water-saving shower heads and aerators are deliberately designed for lower water flow, making them feel weaker than older, higher-flow variants – even though the actual pressure in the pipe has not dropped.

• Water-saving shower heads mix more air into the water to create the sensation of a stronger jet with less water – some users still perceive this as weaker.
• Comparing an old and new tap in the apartment might make it seem like the overall pressure has changed, when in reality, the appliance designs simply differ.
• If you're unsure whether the problem is with the appliance or the pipework, test the pressure at several different taps and compare the results.

Step-by-Step Home Diagnosis

Before calling a specialist, it's worth going through a simple self-check sequence that helps quickly pinpoint whether it's a local or shared problem.

• Check the pressure at several taps in your apartment – if the problem is only in one place, the cause is likely local.
• Ask a neighbour or the apartment association representative if they have also noticed similar fluctuations at the same time.
• Observe whether the pressure changes repeatedly at a specific time (peak hours) or unexpectedly and irregularly (technical fault).
• Clean the aerator and filter first – this is the quickest and cheapest step, solving a large proportion of local cases.
• Write down dates, times, and a description – this information will significantly speed up problem resolution if you contact the apartment association or a specialist.
• If the problem recurs following the same pattern (e.g., every morning at 7–8 AM), this is further confirmation that it's a peak consumption issue, not an isolated technical fault.