How does old plumbing affect drinking water quality?

Why the age of your plumbing affects drinking water quality

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

The inner 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 growth medium for microorganisms. The older the plumbing, the thicker and more uneven this layer usually becomes, and the greater the likelihood that the water quality at the tap will differ from what originally came from the mains supply or well.

This means that the source of a water quality problem might not be the mains supply or well itself – water can enter the property meeting all requirements but degrade as it passes through the building'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 simultaneously changes three things: the internal diameter of the pipe narrows as the rust layer thickens; the inner surface of the pipe becomes uneven, promoting sediment build-up; and metal ions begin to leach into the water. While harmless in normal quantities, increased concentrations over long periods 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 system – and along with corrosion, other, more sensitive substances can also enter the water.

Biofilm: The invisible layer on the inner surface of pipes

Almost every water plumbing system gradually develops a thin layer of microorganisms, mineral particles, and organic matter on the inner surfaces of pipes, known as biofilm. In new, smooth pipes, biofilm is thin and stable, causing no problems. However, in old, corroded, and uneven-surfaced pipes, biofilm has much more area to adhere to and grows thicker.

Biofilm itself is not automatically dangerous – most microorganisms living within it are harmless. Problems arise when conditions within or beneath the biofilm favour the proliferation of undesirable bacteria, especially if water remains stagnant in the pipes for long 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 iron, zinc, or copper content, originating from the pipe material itself.
• An earthy or musty taste most often points to biofilm or water that has been stagnant in the terminal sections of the plumbing for too long.
• A strengthening or weakening chlorine smell might indicate that the water has been in the pipes longer than usual.
• A sulphur or rotten egg smell is typically related to the well water itself, rather than the plumbing, but it can worsen if water sits stagnant in a warm environment for an extended period.

Lead, zinc, and other metals – when should you be concerned?

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

Zinc, on the other hand, is a more common problem because galvanised steel pipes are very typical in old Estonian apartment buildings and private homes. The internal zinc layer 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 has significantly worn down, meaning the pipe's own corrosion is also well advanced.

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

• Lead does not typically give water a taste or colour – it cannot be detected by the senses, only through analysis.
• Zinc often imparts a recognisable bitter-metallic taste even before the amount becomes concerning.
• Copper (common in older plumbing systems) in larger quantities can give water a bluish-green tint on sanitary fittings and a metallic taste.
• If the property was built before the 1990s and the plumbing has not been replaced, it is advisable to be more cautious about lead content.

The effect of stagnant water on drinking water quality

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

This effect is particularly strong in long, rarely used pipe sections – for example, in a guest room, summer house, rarely used sink, or an empty flat. It is also an important issue in properties where overall water usage is low, as the water then moves more slowly through the plumbing and stands 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 does not 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-surfaced pipes offer more living space 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 numbers can increase to a level that is problematic in terms of drinking water quality standards.

This risk is higher in buildings where parts of the plumbing are rarely used – such as empty flats, seasonally used premises, or additional fixtures that are 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 influences when and how problems arise.

• Galvanised steel pipes – 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, so old connections can become leaky.
• Copper pipes – more resistant to corrosion than steel, but in old systems, soldering 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 appear only 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 upgrade – the individual apartment owner or the apartment association as a whole. The answer depends on whether the problem is located in the common property riser or within 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 similar complaints come from several apartments on the same riser or throughout the entire building, it indicates a general aging of the common property plumbing, which is the association's responsibility to address and should be discussed at a general meeting along with a long-term renovation plan.

• Before making major decisions, it is advisable to have water tests done in several apartments simultaneously to determine if the problem is local or building-wide.
• Replacing risers planned at the association level is more cost-effective in the long run than solving individual internal apartment problems year after year.
• When a new resident moves in, it is always wise to ask the association when the plumbing was last inspected or upgraded to anticipate potential problems.

Which water test to conduct if you suspect a plumbing problem

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

• Metal analysis (iron, manganese, zinc, copper, lead) – most relevant if you suspect the problem originates from the plumbing material.
• Microbiological analysis – necessary if you suspect a hygiene problem, for example, after a long period 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 is also worth including an analysis of natural indicators (iron, manganese, hardness, pH), as these also affect how quickly the plumbing itself corrodes.

What to do if the test confirms a problem

The test result determines the sensible next step. If the problem is borderline or minor, a water treatment device (e.g., 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 at one tap, does not solve the problem for the entire house or stop the aging of the plumbing itself – it only alleviates the symptom at one point. If the plumbing is already so old that it affects drinking water quality in several places simultaneously, it is worth considering a more systematic renovation, which you can read more about in our separate guide on the need for old water pipe renovation.

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. Since young children are more sensitive to heavy metals, such as lead and zinc, than adults, it is advisable to be more cautious in such cases.

The general recommendation is to always use cold water for cooking, 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 test specifically for lead content before using it for baby food preparation, or to use bottled water 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 down its deterioration before a major investment.

• Regularly run water through rarely used taps to prevent long-term water stagnation in the pipes.
• Always use cold water for drinking and cooking, not from the hot water tap, as hot water dissolves metals more quickly.
• Periodically clean and maintain mixers and aerators, where sediment can accumulate and also affect taste.
• If the plumbing is known to be old, have water tests done 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 complete renovation is not yet planned.