How does old plumbing affect drinking water quality?

Why the age of plumbing affects drinking water quality

Every plumbing material is initially designed for a specific lifespan. During this period, the internal surface of the pipe is considered relatively stable – water flows through it without significantly reacting with the pipe material. However, over years and decades, this balance changes.

The internal surface of metal pipes (especially galvanised steel) begins to corrode over time, forming a layer that both releases substances into the water and provides a breeding ground for microorganisms. The older the plumbing, the thicker and more uneven this layer usually is, and the greater the likelihood that the water quality at the tap will differ from what originally entered from the mains supply or borehole.

This means the source of a water quality problem might not be the water supply or borehole itself – water can enter the property meeting all standards, but deteriorate as it passes through the property's old plumbing system.

Corrosion: how pipe material dissolves into water

Corrosion is an electrochemical process where metal reacts with water and dissolved gases (primarily oxygen), forming rust, or iron oxides. This process is slow but continuous and accelerates if the water's chemical composition is less compatible with the pipe material – for example, if the water is more acidic or contains more dissolved oxygen.

Corrosion results in three simultaneous changes: the pipe's internal diameter narrows as the rust layer thickens; the internal surface becomes uneven, which promotes sediment build-up; and metal ions begin to dissolve into the water. In normal quantities, these are harmless, but in increased concentrations over long periods, they can affect both the water's taste and its suitability for drinking.

Although iron itself is not typically an acute health hazard in large quantities, elevated iron content indicates active corrosion in the plumbing – and other, more sensitive substances can also enter the water along with corrosion by-products.

Biofilm: an invisible layer on the internal pipe surface

Almost every water plumbing system develops a thin layer of microorganisms, mineral particles, and organic matter on the internal surfaces of pipes over time, known as biofilm. In new, smooth pipes, biofilm is thin and stable and doesn't cause problems. However, in old, corroded pipes with uneven surfaces, biofilm has much more area to attach to and grows thicker.

Biofilm itself isn't automatically dangerous – most microorganisms living within it are harmless. The problem arises when conditions within or beneath the biofilm favour the proliferation of undesirable bacteria, especially if water remains stagnant in the pipe for prolonged periods and the water temperature is warm.

Biofilm also affects the taste and odour of water: water passing through this layer can acquire a slightly earthy, musty, or metallic taste, even if microbiological indicators are within normal limits.

Why water tastes or smells different in old plumbing

Taste and odour are often the first signs people notice – long before a problem is severe enough to exceed regulatory limits. Water from old plumbing might taste metallic, slightly rusty, earthy, or unusually 'heavy' for cold water.

• A metallic taste usually indicates elevated levels of iron, zinc, or copper, originating from the pipe material itself.
• An earthy or musty taste most often points to biofilm or water that has been standing for a long time in the furthest sections of the plumbing.
• A strengthening or weakening of the chlorine smell can indicate that water has been stagnant in the pipes longer than usual.
• A sulphurous or 'rotten egg' smell is typically related to the borehole water itself, rather than the plumbing, but it worsens if water stands in a warm environment for extended periods.

Lead, zinc, and other metals – when to worry

The most sensitive issue regarding old plumbing and drinking water quality is the leaching of heavy metals, especially lead, into the water. Lead pipes are not as widespread in Estonian construction as in some other countries, but in older buildings, lead can still be found in individual fittings, soldering materials, or very old service lines.

Zinc, in contrast, is a more common problem because galvanised steel pipes are very typical in old Estonian apartment buildings and private homes. The internal zinc coating in these pipes protects the steel from corrosion, but over time this layer wears away and partially dissolves into the water, especially if the water is more acidic or softer.

A small amount of zinc in water is not usually a health hazard, but elevated levels can give the water a bitter or metallic taste and indicate that the protective layer is significantly worn, meaning that the pipe's own corrosion is already well advanced.

The situation with lead is more serious, as lead is hazardous to health even in small quantities and its effects are cumulative, especially for young children and pregnant women. If the property has very old plumbing or there is a suspicion of old soldering materials, it is advisable to have a water analysis specifically targeting lead content performed.

• Lead typically does not impart taste or colour to water – it cannot be detected by senses, only by analysis.
• Zinc often gives a recognisable bitter-metallic taste even before the quantity becomes a concern.
• Copper (common in older plumbing systems) can, in larger quantities, give a bluish-green tint to plumbing fixtures and a metallic taste.
• If the property was built before the 1990s and the plumbing has not been replaced, extra caution regarding lead content is warranted.

The effect of stagnant water on drinking water quality

Water that remains stagnant in pipes for extended periods deteriorates in quality in several ways simultaneously. Firstly, it has more time to react with the pipe's internal surface, increasing the amount of dissolved metals. Secondly, residual chlorine content in the water decreases over time, meaning the water's natural protection against microbes weakens. Thirdly, stagnant water heats up to the ambient temperature of the pipe's surroundings, which can promote microbial growth during warm seasons.

This effect is particularly strong in long, rarely used pipe sections – for example, in a guest bathroom, summer home, infrequently used sink, or an unoccupied flat. It is also a significant issue in properties with generally low water consumption, as water then moves slower through the plumbing and remains stagnant for longer, even if no one has been away for an extended period.

A simple but effective measure is to let the tap run for a few minutes before drawing drinking water, especially in the morning or after a long absence. This doesn't solve the root cause but reduces the risk that the first few litres contain more dissolved substances and less fresh chlorine.

Microbiological risk in old plumbing

In addition to chemical indicators, old plumbing also affects the microbiological quality of drinking water. Corroded and uneven pipe surfaces offer more living environment for biofilm and, consequently, microorganisms than new, smooth pipes. In most cases, these microorganisms are harmless, but under certain conditions (warm stagnant water, low residual chlorine, long unused pipe sections), their number can grow to a level that is problematic from the perspective of drinking water quality standards.

This risk is higher in buildings where part of the plumbing is rarely used – for example, empty flats, seasonally used rooms, or additional equipment not used regularly. Regular water exchange in these sections significantly reduces the risk without replacing the plumbing.

How different pipe materials affect drinking water quality

The impact of old plumbing on drinking water quality is not uniform across all materials – each pipe material has its typical risks and lifespan, which affects when and how problems arise.

• Galvanised steel pipes – the most common in older Estonian buildings, prone to internal corrosion and wear of the zinc layer, causing a metallic taste and a drop in water pressure over time.
• Cast iron pipes – primarily used for drainage, but in some cases for water supply; corrode slower than steel but are heavy and brittle, meaning old joints can become leaky.
• Copper pipes – more corrosion-resistant than steel, but in older systems, solder joints may contain tin-based materials that require attention if the plumbing is very old.
• Plastic pipes (PEX, PP-R) – the most common choice in modern homes, virtually corrosion-free and do not significantly affect water taste or chemical composition, making them the most stable long-term option.
• If a building uses several different materials simultaneously, for example, an old galvanised main pipe with later copper branches, the problem may only appear in certain parts of the building, not uniformly throughout the entire property.

Apartment association and individual owner responsibility for plumbing condition

In apartment buildings, water quality issues often raise the question of who is responsible for the condition of the plumbing and its renewal – the individual apartment owner or the apartment association as a whole. The answer depends on whether the problem lies within the common property risers or the specific apartment's internal plumbing.

If water quality deteriorates only in one apartment, the problem is likely within that apartment's internal pipes, for which the owner is responsible. However, if a similar complaint comes from several apartments on the same riser or throughout the building, it indicates general aging of the jointly owned plumbing. Addressing this is the responsibility of the association and should be discussed at a general meeting as part of a long-term renovation plan.

• Before making major decisions, it's advisable to have water analysis performed in several apartments simultaneously to determine if the problem is localised or affects the entire building.
• Planned riser replacement at the association level is more cost-effective in the long run than solving individual in-apartment problems year after year.
• When a new resident moves in, it is always worth asking the association when the plumbing was last inspected or renewed to anticipate potential problems.

Which water analysis to perform if you suspect a plumbing problem

If the taste, odour, or appearance of your water raises concerns, water analysis is the only way to get an objective answer. Different analyses cover different indicators, so it's important to choose the correct type of analysis based on your suspicion.

• Metal analysis (iron, manganese, zinc, copper, lead) – most relevant if you suspect the problem originates from the pipe material.
• Microbiological analysis – necessary if you suspect a hygiene issue, for example, after long periods of stagnation or an unusual odour.
• General drinking water quality analysis – suitable for an initial overview if it's not yet clear which indicator is causing the problem.
• For well water, it's also worth adding an analysis of natural indicators (iron, manganese, hardness, pH), as these also affect how quickly the plumbing itself corrodes.

What to do if analysis confirms a problem

The analysis result determines the appropriate next step. If the problem is borderline or minor, a water treatment device (such as an iron and manganese filter) or simply more regular water flushing in rarely used pipe sections might suffice. If the problem is more serious – for example, confirmed elevated lead or microbiological indicators – the only truly permanent solution is to replace the damaged pipe section or the entire plumbing system.

An intermediate solution, such as installing a filter only on one tap, does not solve the problem throughout the house or stop the aging of the plumbing itself – it merely alleviates the symptom at one point. If the plumbing is already so old that it affects drinking water quality in several places simultaneously, a more systematic renovation should be considered, which you can read about in more detail in our separate guide on the necessity of renovating old water pipes.

Is water from old plumbing suitable for preparing baby food and formula?

Families with young children often ask whether tap water in a house with old plumbing is suitable for preparing baby food or formula. As infants are more sensitive to the effects of heavy metals, such as lead and zinc, than adults, it is advisable to be more cautious in such cases.

The general recommendation is always to use cold water for food preparation, never from the hot water tap, as hot water dissolves metals from pipe walls more quickly. If the plumbing is known to be old or the house was built before the 1990s, it is advisable to have at least one water analysis focusing on lead content performed before using it for baby food preparation, or to use bottled water for this purpose until the situation is clear.

How to maintain drinking water quality with old plumbing

While a complete plumbing replacement is the ultimate solution, there are several steps you can take to improve drinking water quality or slow its deterioration before a major investment.

• Regularly flush rarely used taps to prevent water from stagnating in the pipes for long periods.
• Always use cold water for drinking and cooking, not from the hot water tap, as warm water dissolves metals faster.
• Periodically clean and maintain taps and aerators, where sediment can accumulate and also affect taste.
• If the plumbing is known to be old, have water analysis performed regularly, not just when a problem becomes visible.
• Consider prioritising the replacement of the oldest and most sensitive pipe sections (e.g., the kitchen drinking water branch) if a full renovation isn't yet planned.