---
title: "Pipe Materials and Long-Term Water Quality: Copper, Stainless, Plastic and Galvanised Compared"
source_url: https://legionella.io/articles/pipe-materials-and-long-term-water-quality-copper-stainless-plastic-galvanised/
canonical_url: https://legionella.io/articles/pipe-materials-and-long-term-water-quality-copper-stainless-plastic-galvanised/
pillar: "Best Practice & Future of Legionella Control"
summary: "How copper, stainless, PEX, uPVC and legacy galvanised pipe age over decades, and what corrosion, roughness, biofilm and leaching mean for Legionella risk"
primary_keyword: "pipe materials and water quality"
date_published: 2026-06-26
date_reviewed: 2026-06-26
author: "Legionella.io editorial team (REMOTE TECH LTD)"
reviewed_against: "HSE L8 and HSG274 guidance"
region: "United Kingdom"
license: "CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Quote, adapt or republish with attribution to REMOTE TECH LTD and a link to source_url."
license_url: https://creativecommons.org/licenses/by/4.0/
---

# Pipe Materials and Long-Term Water Quality: Copper, Stainless, Plastic and Galvanised Compared

Every pipe is a habitat as well as a conduit. What it is made from shapes how scale, corrosion and biofilm build on its inner wall over decades, and that slowly shifts the conditions Legionella needs. Material is not a control in its own right, but it is a factor worth understanding when you specify or assess a system.

Most of the time you do not choose pipe material on a blank sheet. You inherit it, or you specify a section on a refurbishment. The useful question is rarely "which is best" in the abstract, but how each common material behaves over a twenty-, thirty- or forty-year service life, and what that behaviour means for the water quality and risk profile you have to manage.

## The decision you are actually weighing

In the UK, five materials cover almost everything you will meet: copper, stainless steel, cross-linked polyethylene and polybutylene plastics (PEX and PB), unplasticised PVC (PVC-U/uPVC), and legacy galvanised steel. New design and installation should follow recognised practice such as BS EN 806 and BS 8558, and every product in contact with wholesome water should be approved under the Water Supply (Water Fittings) Regulations, typically through WRAS [3][4]. Material choice is a designer's and competent person's decision, taken in the round and informed by the risk assessment, not a retrofit shortcut you reach for after a poor sample result.

Four characteristics matter for water quality and Legionella risk over time:

- **Corrosion resistance**, whether the pipe wall stays intact and clean, or sheds rust, scale and metal into the water.
- **Internal surface and roughness**, a rougher bore gives biofilm more to grip; a smooth one is easier to keep clean but never immune.
- **Ageing and leaching**, what the material releases, harbours or develops as it gets old: deposits, taste and odour, or by-products.
- **Compatibility with the regime**, particularly whether it tolerates the hot-water temperatures and any chemical disinfection your control scheme relies on.

None of these decides risk on its own. They sit alongside the things that actually control Legionella: keeping hot water hot, cold water cold, water moving, and surfaces clean [2].

## The five materials compared

The table below sets out how each behaves across those axes. Treat the ratings as general tendencies to verify against the relevant material standards and your own water chemistry, not fixed guarantees.

| Material | Corrosion behaviour | Internal surface & biofilm tendency | Ageing & water-quality issues | Where it sits today |
|---|---|---|---|---|
| **Copper** | Generally good; can suffer pitting or erosion-corrosion in aggressive or fast-flowing waters | Relatively smooth when new; some reported antimicrobial tendency but not self-sterilising | Can release copper and form scale in hard water; usually long-lived if water chemistry suits it | The long-standing UK workhorse for hot and cold distribution |
| **Stainless steel** | Very high resistance in clean potable water | Smooth bore, low fouling tendency | Durable and stable; cost and jointing are the practical constraints | Common in healthcare and higher-risk or premium installations |
| **PEX / PB plastics** | Immune to the metallic corrosion that affects steel and copper | Smooth bore, but biofilm still forms readily on all plastics | Possible permeability, taste/odour or solvent-sensitivity concerns; check hot-water temperature rating | Widely used in modern domestic and commercial pipework |
| **PVC-U / uPVC** | Corrosion-immune | Smooth, but typically cold-water and non-pressure roles | Can become brittle with age and UV; limited hot-water use | Cold supply, waste and specific cold applications |
| **Galvanised steel** | Poor over time; zinc layer depletes, then steel corrodes | Becomes rough and tuberculated as rust builds | Tuberculation, rust deposits, restricted bore and discoloured water | Legacy material; generally replaced on a planned basis, not specified new |

## Reading the table: which material, and when

**Copper** remains the default many UK systems are built from, and it is well understood. Its weak points are specific: certain aggressive water chemistries can pit it, excessive flow velocity can erode it, and in hard-water areas it scales like anything else, which is the link to [Does hard water, scale and iron increase Legionella risk? The water chemistry that feeds growth](https://legionella.io/articles/does-hard-water-cause-legionella/). Copper has a reputation for discouraging microbial growth, and there is laboratory support for some effect, but it is not a disinfectant and not self-sterilising. Biofilm and Legionella can establish on copper as on anything else, so copper is never a reason to relax temperature or flushing control.

**Stainless steel** is the quiet performer: very corrosion-resistant, a smooth bore that resists fouling, and stable over a long life. The constraints are cost and jointing competence rather than water quality, which is why it tends to appear where the consequences of failure are highest.

**Plastics (PEX, PB, uPVC)** remove metallic corrosion from the equation entirely, which is a genuine advantage in aggressive waters, and their bore is smooth when new. The trade-offs are different in kind: some plastics carry reported permeability or taste-and-odour issues and can be sensitive to certain solvents, and crucially their temperature rating governs whether they suit hot-water duty at the temperatures a thermal control scheme needs. Smoothness is not sterility, biofilm attaches to plastic readily, so the same flushing and temperature discipline applies.

**Galvanised steel** is the one to recognise rather than recommend. As the protective zinc depletes, the steel beneath corrodes, the bore roughens and tuberculates, and the system starts shedding rust and harbouring deposits in exactly the rough, low-flow pockets that shelter biofilm and the sediment it feeds on. Where a survey finds galvanised pipework still in service, its condition belongs in the risk assessment and usually points toward planned replacement, prioritised by condition rather than ripped out overnight.

## What material choice cannot do for you

No pipe material is self-sterilising, and none detects or prevents contamination. Every material here will grow biofilm given the right temperature, nutrients and stagnant water, and material condition is an indicator that should prompt inspection, never a verdict that a system is safe or unsafe. The controls remain temperature, turnover and cleanliness, with sampling used to inform the picture [1][2]. Choosing copper, stainless or a well-rated plastic on a new installation removes some failure modes and buys easier long-term maintenance; it does not buy you out of running the system properly.

This is general guidance, not a specification. The right material for a given building depends on its water chemistry, its temperature and disinfection regime, the application and the standards in force, and that judgement belongs to a competent designer working from a site-specific risk assessment under BS 8580-1 [5]. Nothing here is design, legal or medical advice.

## FAQ

### Does copper pipework stop Legionella growing?

No. Copper has some reported antimicrobial tendency and a good service record, but it is not a disinfectant and not self-sterilising. Biofilm and Legionella can colonise copper wherever water sits warm and still. Copper is a reasonable, well-understood material, not a substitute for temperature and flow control.

### Is plastic pipe such as PEX worse than copper for biofilm?

Not inherently worse, but not biofilm-proof either. Plastics avoid metallic corrosion and have a smooth new bore, yet biofilm attaches readily to all plastics. The bigger practical questions for hot water are the material's temperature rating and any taste, odour or permeability characteristics, verify those against the manufacturer's data and the relevant standard rather than assuming plastic is automatically lower-risk.

### We still have old galvanised steel pipes, do they need replacing for Legionella reasons?

Their condition needs assessing. Ageing galvanised steel tends to lose its zinc layer and develop internal rust and tuberculation, roughening the bore and shedding deposits that shelter biofilm and sediment. That makes condition an input to the risk assessment, which may justify planned, prioritised replacement. It is a risk-assessed decision, not an automatic overnight rip-out.

### Can I cut Legionella risk just by choosing the right pipe material?

No single material does that. Better material can remove specific failure modes and make a system easier to keep clean over its life, but the controls that actually keep Legionella in check are temperature, water turnover and cleanliness. Material is one contributing factor the competent person weighs, alongside design, use and maintenance.

## Related reading

- [Does hard water, scale and iron increase Legionella risk? The water chemistry that feeds growth](https://legionella.io/articles/does-hard-water-cause-legionella/)
- [Biofilms: how Legionella hides in plumbing systems](https://legionella.io/articles/biofilms-how-legionella-hides-in-plumbing-systems/)
- [The Water Supply (Water Fittings) Regulations, WRAS and Legionella risk](https://legionella.io/articles/the-water-supply-water-fittings-regulations-wras-and-legionella-risk/)

## Sources

[1] HSE, HSG274 Part 2 (2024), “Water system design and commissioning”, p.63. https://www.hse.gov.uk/pubns/books/hsg274.htm
[2] HSE, ACoP L8 (2013), “Carrying out a risk assessment”, p.12. https://www.hse.gov.uk/pubns/books/l8.htm
[3] BSI, "BS EN 806 / BS 8558, design, installation and maintenance of services supplying water for domestic use within buildings". https://www.bsigroup.com/
[4] WRAS, "Water Regulations Approval Scheme, approved products and materials". https://www.wras.co.uk/
[5] BSI, BS 8580-1:2019, clause 4 (factors to be considered in the risk assessment). https://www.bsigroup.com/